The present invention pertains to a composition for surface treatment, treating liquid for surface treatment, method of surface treatment, and surface-treated metal materials obtained by said treatment method. The composition will allow deposition of a surface coating film with excellent corrosion resistance or bare corrosion resistance after coating the surface of metal material such as building materials and home electrical appliance materials.
The phosphoric acid zinc treatment method or the chromate treatment method is commonly used for deposition of a surface coating film with excellent corrosion resistance on the surface of metal materials after coating. With the phosphoric acid zinc treatment method, a film with excellent corrosion resistance can be deposited on a steel plate or zinc-plated steel plate such as a hot rolled steel plate or cold rolled steel plate.
However, the formation of sludge as a byproduct during the phosphoric acid zinc treatment cannot be avoided. With the chromate treatment method, although sufficient performance can be ensured after coating, there is a tendency to avoid using this method from the standpoint of current environmental regulations because the treatment liquid contains harmful hexavalent chromium.
Therefore, techniques have been developed in recent years to provide the necessary corrosion resistance using a treatment liquid that contains no harmful components and in which sludge does not form. Such techniques involve coating the surface of the base material with a thin film of a metal such as zirconium. Surface treatment methods of the kind described below have been proposed.
For example, in the method described in Patent Reference 1, a non-chrome coating for metal surface treatment that contains a compound having a nitrogen atom with a lone electron pair or that contains the aforementioned compound and a zirconium compound is used. The purpose of this method is to obtain a surface coating film with excellent corrosion resistance and adherence with the use of the aforementioned compositions that contain no harmful hexavalent chromium.
However, the use of this method is limited to metal base materials such as aluminum alloys. Moreover, it is difficult to use this method for coating a material with a complex structure because a coating drying process is required for the formation of the surface coating film.
In the method described in Patent Reference 2, a surface treatment agent and a treatment bath containing selenium, zirconium, phosphoric acid, and fluorine compounds are used for the deposition of a surface coating film with excellent tight bonding and corrosion resistance after coating by means of a formation reaction.
The use of this method, as in the case of the method described in Patent Reference 1, is limited to aluminum or aluminum alloys, which are metal base materials already having excellent corrosion resistance. This method cannot be used for the deposition of a surface coating film on the surface of iron-based material or zinc-based material.
In the method described in Patent Reference 3, a metallic surface treatment composition consisting of a metal acetylacetonate and a water-soluble inorganic titanium compound or water-soluble inorganic zirconium compound is used for the deposition of a surface coating film with excellent corrosion resistance and adherence after coating. This method can be used to treat metal materials other than aluminum alloys, such as magnesium, magnesium alloys, zinc, and zinc plated alloys.
However, this method cannot be used for the deposition of a surface coating film on the surface of iron-based metal materials such as hot rolled steel plate or cold rolled steel plate.
In addition, a metal surface treatment using a chromium-free coating type acid composition has been described in Patent Reference 4. In this metal surface treatment method, an aqueous solution of components capable of forming a film with excellent corrosion resistance is coated on a metal surface and then a baking/drying process is carried out for fixing the formed film without a water washing process. Therefore, no chemical reaction is involved in the formation of the film and thus it is possible to use this method for the deposition of a film on the surface of metals such as hot rolled steel plate, cold rolled steel plate, zinc-plated steel plate, and aluminum alloys.
However, with this method, the film is formed by coating and drying as in the case of the method described in Patent Reference 1 and thus it is difficult to achieve a uniform film coating on a material with a complex structure.
In Patent Reference 5, a metal chemical conversion method using a treatment bath containing zirconium ion and/or titanium ion and fluorine ion is described. This method is applicable to iron-based metal materials as well as aluminum and zinc.
However, this method requires using an oxidizing agent for controlling the iron ion concentration in the chemical conversion agent during the conversion process.
Therefore, this method cannot be used to carry out a highly workable surface treatment capable of depositing a film with excellent corrosion resistance and adherence on metal materials such as iron-based metal materials, zinc-based metal materials, etc., using a treatment liquid containing none of the environmentally harmful components used in the conventional technique.
- Patent Reference 1: Japanese Patent Application No.
2000-204,485 - Patent Reference 2: Japanese Patent Application No.
2[1990]-25,579 - Patent Reference 3: Japanese Patent Application No.
2000-199,077 - Patent Reference 4: Japanese Patent Application No.
5[1993]-195,244 - Patent Reference 5: Japanese Patent Application No.
2004-43913
The purpose of the present invention is to provide a composition for surface treatment, treating liquid for surface treatment, method of surface treatment, and surface-treated metal materials obtained by said treatment method. Said composition will allow deposition of a surface coating film having excellent corrosion resistance or bare corrosion resistance after coating on the surface of metal materials, for example, iron-based metal materials such as hot rolled steel plate, cold rolled steel plate used in building materials and home electrical appliance materials, zinc-based metal materials such as zinc-plated steel plate, etc. Furthermore, said surface treatment method uses a treating liquid that contains none of the environmentally harmful components used in the conventional technique.
We have carried out extensive studies on methods for solving the problems described above and were able to develop a composition for surface treatment, treating liquid for surface treatment, method of surface treatment, and surface-treated metal materials obtained by said treatment method, unlike those of the conventional technique.
The aforementioned problems can be solved by the present inventions as described in sections (1)-(17) given below.
(1) A composition for the surface treatment of metals that contains iron and/or zinc that comprises a component (A), component (B), and component (C) as described below.
- (A) A compound containing at least one element selected from the group consisting of Ti, Zr, Hf, and Si.
- (B) A compound containing Y and/or a lanthanide element.
- (C) Nitric acid and/or a nitric acid compound. In the aforementioned composition, the ratio of the total mass concentration B of the aforementioned Y and/or lanthanide element contained in the aforementioned component (B) to the total mass concentration A of the aforementioned elements contained in the aforementioned component (A), i.e., K1 = B/A, is in the range of 0.05 ≤ K1 ≤ 50 and the ratio of the total mass concentration C of the nitrogen atoms contained in the aforementioned component (C) in terms of the NO3 concentration to the aforementioned total mass concentration A, i.e., K2 = C/A, is in the range of 0.01 ≤ K2 ≤ 200.
(2) A composition for surface treatment as described in the aforementioned (1) that contains a component (D) as described below:
- (D) At least one fluorine-containing compound.
(3) A treatment liquid for the surface treatment of metals containing iron and/or zinc that comprises a component (A), component (B), and component (C) as described below.
- (A) A compound containing at least one element selected from the group consisting of Ti, Zr, Hf, and Si.
- (B) A compound containing Y and/or a lanthanide element.
- (C) Nitric acid and/or a nitric acid compound.
(4) A treatment liquid for surface treatment as described in the aforementioned (3) that contains a component (D) as described below:
- (D) At least one fluorine-containing compound,
and the free fluorine ion concentration D is in the range of 0.001 ppm ≤ D ≤ 300 ppm.
(5) A treatment liquid for surface treatment as described in the aforementioned (3) or (4) having a pH value of no more than 6.0.
(6) A treatment liquid for surface treatment as described in any one of the aforementioned (3)-(5) that contains at least one compound selected from the group consisting of HCl, H2SO4, HClO3, HBrO3, HNO2, HMnO4, HVO3, H2O2, H2WO4, H2MoO4 and their salts in a concentration in the range of 10-20,000 ppm.
(7) A treatment liquid for surface treatment as described in any one of the aforementioned (3)-(6) that contains at least one compound selected from the group consisting of ethylenediamine tetraacetic acid, gluconic acid, heptogluconic acid, glycolic acid, citric acid, succinic acid, fumaric acid, aspartic acid, tartaric acid, malonic acid, malic acid, salicylic acid, and their salts in a concentration in the range of 1-10,000 ppm.
(8) A treatment liquid for surface treatment as described in any one of the aforementioned (3)-(7) that contains a water-soluble polymer compound and/or a water-dispersible polymer compound.
(9) A treatment liquid for surface treatment as described in any one of the aforementioned (3)-(8) that contains at least one surfactant selected from a group consisting of nonionic surfactants, anionic surfactants, and cationic surfactants.
(10) A surface treatment method for metals containing iron and/or zinc that includes a treatment liquid contact process in which a metal material containing iron and/or zinc is brought into contact with the treatment liquid for surface treatment described in any one of the aforementioned (3)-(8).
(11) A surface treatment method for metals containing iron and/or zinc that includes a treatment liquid contact process in which a metal material containing iron and/or zinc is brought into contact with the treatment liquid for surface treatment as described in the aforementioned (9) to simultaneously carry out a degreasing treatment and a film formation treatment on the aforementioned metal material.
(12) A surface treatment method as described in the aforementioned (10) or (11) in which the aforementioned metal material that contains iron and/or zinc is a metal material that has been cleansed by a degreasing treatment.
(13) A surface treatment method as described in any one of the aforementioned (10)-(12) in which the aforementioned treatment liquid contact process involves an electrolytic treatment using the aforementioned metal material that contains iron and/or zinc as a cathode.
(14) A surface treatment method as described in any one of the aforementioned (10)-(13) that includes a process in which the aforementioned metal material that contains iron and/or zinc is brought into contact with an aqueous solution containing at least one of the elements selected from a group consisting of cobalt, nickel, tin, copper, titanium, and zirconium after the aforementioned treatment liquid contact process.
(15) A surface treatment method as described in any one of the aforementioned (10)-(13) that includes a process in which the aforementioned metal material that contains iron and/or zinc is brought into contact with an aqueous solution containing a water-soluble polymer compound or a water-dispersible polymer compound after the aforementioned treatment liquid contact process.
(16) An iron-containing metal material having a surface coating film layer that is formed on the surface of the iron-containing metal material by the surface treatment method described in any one of the aforementioned (10)-(15), that contains the aforementioned elements of the aforementioned component (A) and that has an adhesion quantity in terms of the aforementioned elements of greater than 20 mg/cm2.
(17) A zinc-containing metal material having a surface treatment film layer that is formed on the surface of the iron-containing metal material by the surface treatment method described in any one of the aforementioned (10)-(15), that contains the aforementioned elements of the aforementioned component (A) and that has an adhesion quantity in terms of the aforementioned elements of greater than 15 mg/cm2.
A composition for surface treatment of a metal, treating liquid for surface treatment, method of surface treatment, and surface-treated metal materials obtained by said treatment method of the present invention are epoch-making techniques capable of depositing a surface coating film with excellent corrosion resistance after coating on the surface of the metal material using a treatment bath that contains none of the environmentally harmful components used in the conventional technique.
A composition for surface treatment of a metal of the present invention (also to be called simply "the composition of the present invention" in the following), a treatment liquid for metal surface treatment of the present invention (also to be called simply "the treatment method of the present invention" in the following), and a metal material containing iron and/or zinc of the present invention (also to be called simply "the metal material of the present invention" in the following) will now be described in more detail. The composition and the treatment liquid of the present invention will be explained first.
The composition of the present invention is diluted with water or dissolved in water at the time of its use to form the treatment liquid of the present invention.
The materials to be surface-treated with the treatment liquid of the present invention are iron-based metal materials or zinc-based metal materials.
There are no particular limitations with regard to the kind of iron-based metal materials that can be used as long as they contain iron. Suitable materials would include, for example, steel plate such as cold rolled steel plate, hot rolled steel plate, etc., cast iron, and sintered materials.
There are no particular limitations with regard to the kind of zinc-based metal materials that can be used as long as they contain zinc. Suitable materials would include, for example, zinc die-cast and zinc-containing plated materials. The zinc-containing plated materials consist of zinc or alloys of zinc and at least one other element selected from among, for example, nickel, iron, aluminum, manganese, chromium, magnesium, cobalt, lead, and antimony, and unavoidable impurities. There are no particular limitations with regard to the plating methods that can be used. Suitable methods would include, for example, electroplating methods, fusion plating methods, vapor deposition plating methods, etc.
The present invention pertains to surface treatment of the surface of metal materials. The metal materials can be surface-treated individually or combinations of two or more of them can be treated simultaneously. When two or more metal materials are to be treated simultaneously and when at least one of the metal materials is an iron- or zinc-based metal material, the other metal material can be aluminum, magnesium, nickel, or their alloys. Moreover, the different metals may not be in contact with each other or they can be in contact with each other or joined together by a welding, adhesion, or riveting method.
The functions of the present invention will now be described in detail.
A composition of the present invention contains the component (A), component (B), and component (C) as described below.
Component A is a compound containing at least one element selected from the group consisting of Ti, Zr, Hf, and Si. Suitable compounds include, for example, TiCl4, Ti(SO4)2, TiOSO4, Ti(NO3)4, TiO(NO3)2, Ti(OH)4, TiO2OC2O4, H2TiF6, salts of H2TiF6, TiO, TiO2, Ti2O3, TiF4, ZrCl4, ZrOCl2, Zr(OH)2Cl2, Zr(OH)3Cl, Zr(SO4)2, ZrOSO4, Zr(NO3)4, ZrO(NO3)2, Zr(OH)4, H2ZrF6, salts of H2ZrF6, H2(Zr(CO3)2(OH)2, salts of H2(Zr(CO3)2(OH)2, H2Zr(OH)2(SO4)2, salts of H2Zr(OH)2(SO4)2, ZrO2, ZrOBr2, ZrF4, HfCl4, Hf(SO4)2, H2HfF6, salts of H2HfF6, HfO2, HfF4, H2SiF6, salts of H2SiF6 and Al2O3(SiO2)3. Two or more of these compounds may also be used concomitantly.
Component (B) is a compound containing Y and/or a lanthanide element; i.e., a compound containing at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Suitable compounds include, for example, oxides, sulfates, nitrates, and chlorides of these elements. More specifically, for example, they include yttrium chloride, lanthanide chloride, cerium chloride, praseodymium chloride, neodymium chloride, promethium chloride, samarium chloride, europium chloride, gadolinium chloride, terbium chloride, dysprosium chloride, holmium chloride, erbium chloride, thulium chloride, ytterbium chloride, lutetium chloride, yttrium sulfate, lanthanide sulfate, cerium sulfate, praseodymium sulfate, neodymium sulfate, promethium sulfate, samarium sulfate, europium sulfate, gadolinium sulfate, terbium sulfate, dysprosium sulfate, holmium sulfate, erbium sulfate, thulium sulfate, ytterbium sulfate, lutetium sulfate, yttrium nitrate, lanthanide nitrate, cerium nitrate, praseodymium nitrate, neodymium nitrate, promethium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate, terbium nitrate, dysprosium nitrate, holmium nitrate, erbium nitrate, thulium nitrate, ytterbium nitrate, lutetium nitrate, yttrium oxide, lanthanide oxide, cerium oxide, praseodymium oxide, neodymium oxide, promethium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, and lutetium oxide. Two or more of these compounds may also be used concomitantly.
Component (C) is nitric acid and/or a nitric acid compound. Suitable compounds include, for example, nitric acid, metal nitrates, etc. Metal nitrates would include, for example, ferric nitrate, manganese nitrate, nickel nitrate, cobalt nitrate, silver nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, and calcium nitrate. Two or more of these compounds may also be used concomitantly.
A composition of the present invention is diluted with water or dissolved in water at the time of its use for the surface treatment of a metal. Namely, the treatment liquid for metal surface treatment is prepared and used. In preparing the treatment liquid for metal surface treatment, water is added to the composition for metal surface treatment to bring the total mass concentration of the aforementioned elements (Ti, Zr, Hf, and Si) of the aforementioned component (A) within the range of 10 ppm to 10,000 ppm.
The term "the total mass concentration A of the aforementioned elements contained in the aforementioned component (A)" indicates "the concentration of the aforementioned elements contained in the aforementioned component (A) contained in the composition (in some cases, the treatment liquid) of the present invention".
The same is true for the terms "the total mass concentration B" and "the total mass concentration C".
In the composition for surface treatment and the treatment liquid for surface treatment of the present invention, the ratio of the total mass concentration B of the aforementioned Y and/or lanthanide element contained in the aforementioned component (B) to the total mass concentration A of the aforementioned elements contained in the aforementioned component (A), i.e., K1 = B/A, is in the range of 0.05 ≤ K1 ≤ 50 and the ratio of the total mass concentration C of the nitrogen atoms contained in the aforementioned component (C) in terms of the NO3 concentration to the aforementioned total mass concentration A, i.e., K2 = C/A, is in the range of 0.01 ≤ K2 ≤ 200.
Here, component A is a substance having excellent anti-acid and anti-alkali properties and is the main component of the surface coating film of the present invention.
Component (B) can promote the film deposition of component (A). Moreover, component (B) may be contained in the surface coating film so that the corrosion resistance and bare corrosion resistance of the film after coating can be expected to further improve.
Component (C) in the treatment liquid for surface treatment serves to maintain the stability of the treatment liquid by increasing the solubility of component (A) and component (B). Furthermore, component (C) can also assist the film deposition of component (A), though not as effectively as component (B).
When the aforementioned K1 = B/A is too small, component (B) can not be expected to promote the film deposition of component (A) because of the reduced proportion of component (B). Consequently, the amount of film adhesion of component (A) will decrease compared to that obtained when the total mass concentration ratio of component (A) to component (B), i.e., K1, is within the range of 0.05 ≤ K1 ≤ 50 and the corrosion resistance of the treated metal material may decrease.
When the aforementioned K1 is too large, the reaction initiation point itself of component (A) on the surface of the treated metal material may be lowered and the amount of film adhesion of component (A), that is the main component of the film and the component that provides the corrosion resistance to the film, will decrease even though the film deposition promoting effect of component (B) is present. Therefore, excellent corrosion resistance cannot be obtained and the adherence may also be adversely affected in some cases.
When the aforementioned K2 = C/A is too small, suitable corrosion resistance of the treated metal material cannot be obtained and the treatment liquid stability of the treatment liquid for surface treatment may be adversely affected. Consequently, continuous operation may be hindered. Furthermore, because of the small proportion of component (C) in the treatment liquid, the assisting effect of component (C) on the film deposition of component (A) cannot be expected.
When K2 = C/A is in the range of 0.01 ≤ K2 ≤ 200, it will be sufficient to maintain the stability of the treatment liquid of the present invention. Larger K2 values will not improve the corrosion resistance and thus are economically disadvantageous.
The aforementioned total mass concentration A of the aforementioned component (A) used in the treatment liquid of the present invention is preferably adjusted to be in the range of 10 ppm to 10,000 ppm, and more preferably in the range of 50 ppm to 5,000 ppm. When the aforementioned total mass concentration A is too small, it will become difficult to obtain an amount of adhesion sufficient for acquiring the desired corrosion resistance within a practical treatment time due to the low concentration of the film main component, even though the aforementioned K1 and the aforementioned K2 are within the specified ranges. When the aforementioned total mass concentration A is too large, although a sufficient amount of adhesion can be obtained, the corrosion resistance cannot be improved further and thus an excessively high total mass concentration A is not economically desirable.
It is desirable that the composition and treatment liquid of the present invention additionally contain at least one fluorine-containing compound as component (D). Suitable compounds include, for example, hydrofluoric acid, H2TiF6, salts of H2TiF6, TiF4, H2ZrF6, salts of HZZrF6, ZrF4, H2HfF6, salts of H2HfF6, HfF4, H2SiF6, HBF4, salts of HBF4, NaHF2, KHF2, NH4HF2, NaF, KF, and NH4H. Two or more of these fluorine-containing compounds may also be used concomitantly.
When component (D) is to be added to the treatment liquid of the present invention, the concentration of at least one of the fluorine-containing compounds of component (D) is preferably adjusted so that the free fluorine ion concentration D will be in the range of 0.001 ppm to 300 ppm, and more preferably in the range of 0.1 ppm to 100 ppm. Here, the term "free fluorine ion concentration D" means the fluorine ion concentration determined with the use of a commercially available ion electrode. When the free fluorine ion concentration D is too high, the etching reaction on the raw material surface by HF will be too excessive and the amount of film deposition sufficient to achieve corrosion resistance of the surface of the treated metal material will tend to become difficult to obtain. The corrosion resistance of the surface of the treated metal material can be achieved even when the free fluorine ion concentration D produced by the fluorine-containing compound of component (D) is too small, but the stability of the treatment liquid for surface treatment may be adversely affected and continuous operation may be hindered.
Film deposition by the treatment liquid of the present invention is preferably induced by the formation reaction accompanying the etching of the metal base material. Therefore, the treatment is preferably carried out in a pH range in which an etching reaction will ordinarily occur, i.e., a pH value below 6.0, preferably below 5.0, and more preferably below 4.0.
There are no particular limitations with regard to the kind of reagent used for adjusting the pH of the treatment liquid of the present invention when needed. For example, acids such as hydrochloric acid, sulfuric acid, boric acid, and organic acids, alkalis such as lithium hydroxide, potassium hydroxide, sodium hydroxide, calcium hydroxide, magnesium hydroxide, barium hydroxide, alkali metal salts, ammonia, ammonium salts, and amines may be used.
A treatment liquid of the present invention may be contaminated by the metals contained in the base material which are eluted out by the etching reaction of the base material, or by the metals or compounds contained in the tap water and industrial water because component (B) can promote the film deposition of component (A) and the film deposition of component (A) will not be affected by other metal elements.
An anion component is preferably added to the treatment liquid of the present invention to further promote the film-formation reaction. Suitable anion components that may be added to the treatment liquid for surface treatment of the present invention include, for example, HCl, H2SO4, HClO3, HBrO3, HNO2, HMnO4, HVO3, H2O2, H2WO4, H2MoO4, etc. There are no particular limitations with regard to the concentration of the anion component added; a concentration in the range of about 10 ppm to 20,000 ppm is sufficient for providing the desired effect.
When the treatment load of the metal material to be treated is high for the treatment liquid of the present invention, a chelating agent capable of chelating metal ions dissolved out by the etching reaction is preferably added. Suitable chelating agents that can be used in the treatment liquid of the present invention include, for example, ethylenediamine tetraacetic acid (EDTA), gluconic acid, heptogluconic acid, glycolic acid, citric acid, succinic acid, fumaric acid, aspartic acid, tartaric acid, malonic acid, malic acid, salicylic acid, and their salts. There are no particular limitations with regard to the content of these chelating agents. For example, a concentration in the range of about 1 ppm to 10,000 ppm is sufficient for providing the desired effect.
A water-soluble polymer compound and/or a water-dispersible polymer compound having an ionic reactive group in their molecule are preferably added to the treatment liquid of the present invention. Suitable compounds include, for example, copolymers of polyvinyl alcohol, poly(meth)acrylic acid or acrylic acid, and methacrylic acid, copolymers of ethylene and acryl-type monomers such as (meth)acrylic acid, (meth)acrylate, etc., copolymers of ethylene and vinyl acetate, polyurethane, amino modified phenol resins, polyester resins, epoxy resins, polyamide amines, polyamines, polyamine derivatives, polyallyl amines, polyallyl amine derivatives, polyamide amine derivatives, polyvinyl amine, polyvinyl amine derivatives, tannin, tannic acid and its salts, and phytic acid. There are no particular limitations with regard to the concentration of the aforementioned compounds added, but a concentration in the range of 1 ppm to 10,000 ppm is preferable. This addition quantity should give a sufficient effect.
At least one surfactant selected from a group consisting of nonionic surfactants, anionic surfactants, and cationic surfactants is preferably added to the treatment liquid of the present invention. When a treatment liquid for surface treatment of this kind is used for the surface treatment of a metal base material, as will be mentioned later, a good film can be formed without a preliminary degreasing treatment or cleansing treatment of the metal material to be treated. Namely, the treatment liquid for surface treatment of the present invention can be used as a degreasing surface treatment agent as well as a formation surface treatment agent.
The treatment method of the present invention is a surface treatment method for metals containing iron and/or zinc that includes a treatment liquid contact process in which the metal material containing iron and/or zinc is brought into contact with the treatment liquid of the present invention.
The only requirement of the surface treatment method of the present invention is to bring the aforementioned metal material containing iron and/or zinc into contact with the aforementioned treatment liquid of the present invention. In this way a film made of oxides and/or hydroxides of the aforementioned elements of the aforementioned component (A) will be deposited on the surface of the metal base material and a surface coating film layer with excellent adherence and corrosion resistance can thus be formed.
Any method such as a spray treatment, immersion treatment, or cast liquid treatment [unconfirmed -- Tr. Ed.] can be used for the contact treatment mentioned above; the contact method used will not affect the performance of the film formed.
It is chemically difficult to obtain the hydroxide of metals contained in the film of the aforementioned component (A) in the form of a pure hydroxide. In general, therefore, oxides of the aforementioned metals with attached water of hydration are also included in this group of oxides. Therefore, the aforementioned hydroxides of metal will eventually become oxides by heating. As for the structure of the surface coating film of the present invention, it is believed that the film is present in the state of a mixture of oxides and hydroxides when the film is dried at normal temperature or a low temperature after the surface treatment, whereas the film is present in a state in which oxides only or oxides as the majority component are present when the film is dried at a high temperature after the surface treatment.
The aforementioned metal material containing iron and/or zinc is preferably subjected to a cleansing process, such as a degreasing treatment. There are no particular limitations with regard to the method used for degreasing, i.e., any conventional method can be used.
As mentioned before, when the treatment liquid of the present invention contains the aforementioned surfactant, a good film can be formed even without pre-cleansing of the aforementioned metal material containing iron and/or zinc by a degreasing treatment. Namely, in this case, the degreasing treatment and the film-forming treatment of the aforementioned metal material containing iron and/or zinc are carried out at the same time.
There are no particular limitations with regard to the condition of use of the treatment liquid of the present invention.
The reactivity of the treatment liquid of the present invention can be controlled freely by changing the ratio of the aforementioned total mass concentration B to the aforementioned total mass concentration A, i.e., K1 = B/A, and the ratio of the aforementioned total mass concentration C to the aforementioned total mass concentration A, i.e., K2 = C/A.
Furthermore, even when at least one of the aforementioned component (D) fluorine-containing compounds is used, the reactivity can still be controlled by changing the free fluorine ion concentration D. The treatment temperature and treatment time can be altered freely in accordance with the reactivity of the treatment bath.
In the treatment method of the present invention, an electrolytic treatment with the aforementioned metal material containing iron and/or zinc as the cathode can be carried out while the metal material is in the state of contact with the treatment liquid of the present invention.
In this case, a hydrogen reducing reaction will occur at the interface of the aforementioned metal material containing iron and/or zinc serving as the cathode and the pH will rise. With a rising pH, the stability of the compound containing the elements of component (A) at the cathode interface will decrease and the surface treatment film will be deposited as an oxide or as a water-containing hydroxide.
After the aforementioned metal material containing iron and/or zinc has made contact with the treatment liquid of the present invention or has been subjected to an electrolytic treatment following such contact, it may then be brought into contact with an acidic aqueous solution containing at least one element selected from a group consisting of cobalt, nickel, tin, copper, titanium, and zirconium or with a treatment solution containing at least one water-soluble polymer compound and/or water-dispersible polymer compound. In this way, the effect of the present invention can be further enhanced.
A surface coating film obtained by the present invention is a thin film with excellent coating performance. When the surface condition of the metal material to be treated shows the presence of an abnormality, the surface treatment film layer may end up with a very small defective portion. Therefore, the metal material is brought into contact with the acidic aqueous solution containing at least one element selected from a group consisting of cobalt, nickel, tin, copper, titanium, and zirconium or with a treatment solution containing at least one water-soluble polymer compound and/or water-dispersible polymer compound. In this way, any defective portion can be covered and the corrosion resistance can be further improved.
There are no particular limitations with regard to the source of supply of the aforementioned at least one element selected from a group consisting of cobalt, nickel, tin, copper, titanium, and zirconium. Readily available oxides, hydroxides, fluorides, complex fluorides, chlorides, nitrates, oxynitrates, sulfates, oxysulfates, carbonates, oxycarbonates, phosphates, oxyphosphates, oxalates, oxyoxalates, and organometal compounds of the aforementioned metal elements can be used. The acidic aqueous solution containing the aforementioned metal elements preferably has a pH value in the range of 2-6. Acids such as phosphoric acid, nitric acid, sulfuric acid, hydrofluoric acid, hydrochloric acid, and organic acids, and alkalis such as sodium hydroxide, potassium hydroxide, lithium hydroxide, alkali metal salts, ammonia, ammonium salts, and amines can be used for pH adjustment.
The aforementioned at least one polymer compound selected from among water-soluble polymer compounds and water-dispersible polymer compounds can be, for example, a copolymer of polyvinyl alcohol, poly(meth)acrylic acid or acrylic acid, and methacrylic acid, copolymers of ethylene and acryl-type monomers such as (meth)acrylic acid, (meth)acrylate, etc., copolymers of ethylene and vinyl acetate, polyurethane, amino modified phenol resins, polyester resins, epoxy resins, polyamide amines, polyamines, polyamine derivatives, polyallyl amines, polyallyl amine derivatives, polyamide amine derivatives, polyvinyl amine, polyvinyl amine derivatives, tannin, tannic acid and its salts, and phytic acid.
As was described in detail above, with the present invention, the corrosion resistance of a metal material can be improved markedly by forming a film layer made of the oxides and/or hydroxides of the aforementioned component (A) or a film layer made of a mixture of film layers consisting of the film layer of the aforementioned component (A) and a film layer made of the oxides and/or hydroxides of the metal elements of the aforementioned component (B). Here, any films made of the oxides and/or hydroxides of the aforementioned component (A) are acid and alkali resistant and are chemically stable.
Here, in the actual coated film corrosion environment of a metal, the pH will decrease at the anode portion where the elution of metals takes place and the pH will increase at the cathode portion where a reduction reaction occurs. Therefore, a surface coating film with poor acid and alkali resistance will be dissolved in a corrosive environment and lose its effectiveness. A film made of the oxides and/or hydroxides of the aforementioned component (A) used in the present invention is resistant to both acids and alkalis. In addition, with the present invention, a thin and uniform surface coating film can be formed on the surface of the metal to be treated and thus the superior effect of the present invention can be maintained even in a corrosive environment.
Since the oxides and hydroxides of the metal elements contained in the film can form a network structure through metals and oxygen, the formed film is an excellent barrier film. The corrosion of a metal material will vary depending on the environment in which the metal material is used. In general, however, corrosion will occur under the condition where water and oxygen are present and thus is usually of the oxygen requiring type. Therefore, the corrosion speed will be increased in the presence of components such as chlorides, etc. Since the film layer of the present invention has a barrier effect on water, oxygen, and corrosion-promoting components, it offers an excellent anti-corrosion property.
In addition to the aforementioned component (A) and the aforementioned component (B), the composition and the treatment liquid of the present invention may also contain the aforementioned component (C), the proportions of of which are set to be within specified ranges. Therefore, at the time of deposition of the surface coating film, a formation reaction will also occur. The accompanying formation reaction can sharply increase the adherence property of the film.
Here, in order to utilize the aforementioned barrier effect to increase the corrosion resistance of iron-based metal materials such as cold rolled steel plate, hot rolled steel plate, cast iron, sintered materials, etc., the adhering amount of the surface coating film in terms of component (A) is preferably greater than 20 mg/m2, more preferably greater than 30 mg/m2, and especially greater than 40 mg/m2.
Moreover, in order to increase the corrosion resistance of zinc-based metal materials such as zinc or zinc plated steel plate, zinc electroplated steel plate, etc., the adhering amount of the surface coating film in terms of component (A) is preferably greater than 15 mg/m2, and more preferably greater than 20 mg/m2.
When the adhering amount is too small, the aforementioned barrier effect will not be sufficient and it will be difficult to obtain excellent corrosion resistance.
There are no particular limitations with regard to the upper limit of the adhering amount on the iron-based metal material or zinc-based metal material. However, when the adhesion amount is too large, cracks will readily from in the surface coating film and the process of trying to form a uniform film will become difficult. Therefore, the adhering amount in terms of component (A) for both iron-based materials and zinc-based materials is preferably no more than 1 g/m2, and especially no more than 800 mg/m2.
The effect of the surface treatment liquid and the surface treatment method of the present invention will now be explained in detail with the use of actual examples and comparison examples. The material to be treated, the degreasing agent, and the coating material used were selected arbitrarily from among commercially available products and should not restrict in any way the actual use of the surface treatment liquid and the surface treatment method.
The code designations and description of the plates used in the actual examples and comparison examples are given below.
- SPC (cold rolled steel plate; JIS-G-3141)
- EG (zinc electroplated steel plate; plating quantity 20 g/m2)
The surface treatment in Actual Examples 1-5 and Comparison Examples 1-3 was carried out in accordance with the following treatment process:
Alkaline degreasing → water washing → film formation treatment → water washing → deionized water washing → drying.
In Actual Example 6, the surface treatment was carried out in accordance with the following treatment process:
Alkaline degreasing → water washing → film formation treatment → water washing → post treatment → deionized water washing → drying.
In Actual Example 7, the surface treatment was carried out in accordance with the following treatment process:.
Alkaline degreasing → water washing → electroformation treatment → water washing → deionized water washing → drying.
In Comparison Example 4, the surface treatment was carried out in accordance with the following treatment process:
Alkaline degreasing → water washing → surface preparation → water washing → deionized water washing → drying.
For the alkaline degreasing treatment employed in both the actual examples and comparison examples, Fine Cleaner L4460A (registered trade name, manufactured by Nihon Parkerizing Co., Ltd.) and Fine Cleaner L4460B (registered trade name, manufactured by the Nihon Parkerizing Co., Ltd.) diluted with tap water to 2% and 1.4%, respectively, were sprayed on the plate to be treated at 40°C for 120 seconds.
For the water washing and deionized water washing treatments in both the actual examples and comparison examples, water and deionized water, respectively, were sprayed on the plate to be treated at room temperature for 30 seconds.
The plate was then dried by allowing it to stand in a room at room temperature.
An aqueous zirconium sulfate solution, lanthanide sulfate, and nitric acid were used to prepare a composition for surface treatment with a total mass concentration ratio K1 = B/A = 0.1 and a total mass concentration ratio K2 = C/A = 0.01. The aforementioned composition for surface treatment was diluted with deionized water to adjust the mass concentration of the zirconium element to 8,000 ppm. Sodium hydroxide was then used to obtain a surface treatment liquid with a pH value of 3.2. A test plate that had been degreased and water-washed was immersed in the aforementioned surface treatment liquid at 50°C for 180 seconds for surface treatment.
An aqueous hexafluoro zirconium solution, samarium nitrate, and nitric acid were used to prepare a composition for surface treatment with a total mass concentration ratio K1 = B/A = 2.0 and a total mass concentration ratio K2 = C/A = 50. The aforementioned composition for surface treatment was diluted with deionized water to adjust the mass concentration of the zirconium element to 100 ppm. Hydrofluoric acid and ammonia were then used to obtain a surface treatment treatment liquid with a free fluorine concentration of 25 ppm (fluorine ion meter: IM-55G, manufactured by Toa Denpa Kogyo Co., Ltd.) and a pH value of 3.6. A test plate that had been degreased and water-washed was immersed in the aforementioned surface treatment liquid at 45°C for 150 seconds for surface treatment.
An aqueous zirconium nitrate solution, hafnium oxide, gadolinium oxide, and potassium nitrate were used to prepare a composition for surface treatment with a total mass concentration ratio K1 = B/A = 5.0 and a total mass concentration ratio K2 = C/A = 20. The aforementioned composition for surface treatment was diluted with deionized water to adjust the mass concentration of the zirconium element and the mass concentration of hafnium element to a combined mass concentration of 50 ppm. 100 ppm of succinic acid was added to the liquid thus obtained and then potassium fluoride and lithium hydroxide were used to obtain a treatment liquid for surface treatment with a free fluorine concentration of 20 ppm (fluorine ion meter: IM-55G, manufactured by Toa Denpa Kogyo Co., Ltd.) and a pH value of 4.0. A test plate that had been degreased and water-washed was immersed in the aforementioned surface treatment liquid at 60°C for 120 seconds for surface treatment.
An aqueous zirconium nitrate solution, an aqueous lanthanum chloride solution, erbium oxide, sodium nitrate, and nitric acid-soda were used to prepare a composition for surface treatment with a total mass concentration ratio K1 = B/A = 35 and a total mass concentration ratio K2 = C/A = 100. The aforementioned composition for surface treatment was diluted with deionized water to adjust the mass concentration of the zirconium element to 20 ppm. Hydrofluoric acid and calcium hydroxide were then used to obtain a treatment liquid for surface treatment with a free fluorine concentration of 15 ppm (fluorine ion meter: IM-55G, manufactured by Toa Denpa Kogyo Co., Ltd.) and a pH value of 3.0. A test plate that had been degreased and water-washed was sprayed with the aforementioned surface treatment liquid at 55°C for 120 seconds for surface treatment.
An aqueous titanium nitrate solution, an aqueous hexafluoro silicate solution, praseodymium oxide, and potassium nitrate were used to prepare a composition for surface treatment with a total mass concentration ratio K1 = B/A = 0.4 and a total mass concentration ratio K2 = C/A = 8.0. The aforementioned composition for surface treatment was diluted with deionized water to adjust the mass concentration of the zirconium element and the mass concentration of the silicon element to a combined mass concentration of 2,500 ppm. Ammonium fluoride and ammonia were then used to obtain a treatment liquid for surface treatment with a free fluorine concentration of 100 ppm (fluorine ion meter: IM-55G, manufactured by Toa Denpa Kogyo Co., Ltd.) and a pH value of 2.9. A test plate that had been degreased and water-washed was sprayed with the aforementioned surface treatment liquid at 65°C for 300 seconds for surface treatment.
An aqueous zirconium nitrate solution, an aqueous hexafluoro titanium solution, lanthanum chloride, and iron nitrate were used to prepare a composition for surface treatment with a total mass concentration ratio K1 = B/A = 1.0 and a total mass concentration ratio K2 = C/A = 0.5. The aforementioned composition for surface treatment was diluted with deionized water to adjust the the mass concentration of the zirconium element and the mass concentration of the titanium element to a combined mass concentration of 200 ppm. Ammonium fluoride and potassium hydroxide were then used to obtain a treatment liquid for surface treatment with a free fluorine concentration of 50 ppm (fluorine ion meter: IM-55G, manufactured by Toa Denpa Kogyo Co., Ltd.) and a pH value of 4.2. A test plate that had been degreased and water-washed was immersed in the aforementioned surface treatment liquid at 60°C for 200 seconds for surface treatment. After water washing, the plate was subjected to a post treatment. As for the post treatment liquid used, an aqueous hexafluoro titanium solution and nickel nitrate were used to prepare an aqueous solution with a titanium mass concentration of 200 ppm and a nickel mass concentration in terms of the metal element of 50 ppm. This aqueous solution was heated to 45°C and then sodium hydroxide was used to adjust its pH to 4.5. The solution thus obtained was used in the post treatment.
An aqueous hexafluoro zirconium solution, yttrium sulfate, and nitric acid were used to prepare a composition for surface treatment with a total mass concentration ratio K1 = B/A = 3.0 and a total mass concentration ratio K2 = C/A = 3.0. The aforementioned composition for surface treatment was diluted with deionized water to adjust the mass concentration of the zirconium element to 200 ppm. 50 ppm of EDTA was added to the liquid, then hydrofluoric acid and sodium hydroxide were used to obtain a treatment liquid for surface treatment with a free fluorine concentration of 80 ppm (fluorine ion meter: IM-55G, manufactured by Toa Denpa Kogyo Co., Ltd.) and a pH value of 2.8. A test plate that had been degreased and water-washed was used as a cathode and a carbon electrode was used as an anode to carry out electrolysis under an electrolysis condition [= current density -- Tr. Ed.] of 5A/dm2 in the aforementioned surface treatment liquid at room temperature for 10 seconds for surface treatment.
An aqueous zirconium nitrate solution and nitric acid were used to prepare a composition for surface treatment with a total mass concentration ratio K1 = B/A = 0.01 and a total mass concentration ratio K2 = C/A = 10. The aforementioned composition for surface treatment was diluted with deionized water to adjust the mass concentration of the zirconium element to 100 ppm. Sodium hydroxide was then used to obtain a treatment liquid for surface treatment with a pH value of 3.0. A test plate that had been degreased and water-washed was immersed in the aforementioned surface treatment liquid at 55°C for 180 seconds for surface treatment.
An aqueous hexafluoro zirconium solution, europium oxide, and sodium nitrate were used to prepare a composition for surface treatment with a total mass concentration ratio K1 = B/A = 5.0 and the total mass concentration ratio K2 = C/A = 200. The aforementioned composition for surface treatment was diluted with deionized water to adjust the mass concentration of the zirconium element to 4 ppm. Potassium fluoride and potassium hydroxide were then used to obtain a treatment liquid for surface treatment with a free fluorine concentration of 20 ppm (fluorine ion meter: IM-55G, manufactured by Toa Denpa Kogyo Co., Ltd.) and a pH value of 3.8. A test plate that had been degreased and water-washed was immersed in the aforementioned surface treatment liquid at 60°C for 120 seconds for surface treatment.
An aqueous hexafluoro titanium solution, gallium sulfate, potassium nitrate, and ammonium nitrate were used to prepare a composition for surface treatment with a total mass concentration ratio K1 = B/A = 70 and a total mass concentration ratio K2 = C/A = 50. The aforementioned composition for surface treatment was diluted with deionized water to adjust the mass concentration of the titanium element to 50 ppm. Ammonium fluoride and ammonia were then used to obtain a treatment liquid for surface treatment with a free fluorine concentration of 400 ppm (fluorine ion meter: IM-55G, manufactured by Toa Denpa Kogyo Co., Ltd.) and a pH value of 2.8. A test plate that had been degreased and water-washed was sprayed with the aforementioned surface treatment liquid at 50°C for 150 seconds for surface treatment.
A test plate that had been degreased and water-washed was sprayed at room temperature for 30 seconds with a liquid obtained by diluting Preparen ZN (registered trade name, manufactured by the Nihon Parkerizing Co., Ltd.) (a surface preparation agent) to 0.1% with tap water. The test plate was then immersed in a zinc phosphate formation treatment liquid at 43°C for deposition of a zinc phosphate film. The aforementioned zinc phosphate formation liquid was prepared as follows: Parbond L3020 (registered trade name, manufactured by the Nihon Parkerizing Co., Ltd.) was diluted with tap water to 4.8%. A sodium hydrofluoride reagent in a quantity equivalent to 200 ppm of fluorine was then added at 43°C and the total acidity and free acidity were adjusted to be central values of the catalogue values provided.
The external appearances of the test plates obtained in accordance with the actual examples and comparison examples after the surface treatment were evaluated visually by the naked eye and the adhering quantity of the surface coating film layer was determined with the use of a fluorescence X-ray analyzer (System 3270, manufactured by Rigaku Denki Kogyo Co., Ltd.).
In order to evaluate the coating performance of the surface treatment plates obtained from the actual examples and comparison examples, the coating was carried out according to the following process: cation electrodeposition → deionized water washing → baking → midcoat application → baking → topcoat application → baking.
Cation Electrodeposition: epoxy-based cation electrodeposition coating material (Elecron 9400, manufactured by Kansai Paint Co., Ltd.), voltage 200 V, film thickness 20 µm, baking at 175°C for 20 minutes.
Midcoat Application: aminoalkyd-based coating material (Amilac TP-37 White, manufactured by Kansai Paint Co., Ltd.), spray coating, film thickness 35 µm, baking at 140°C for 20 minutes.
Topcoat Application: aminoalkyd-based coating material (Amilac TM-13 Gray, manufactured by Kansai Paint Co., Ltd.), spray coating, film thickness 35 µm, baking at 140°C for 20 minutes.
The coating performance of the actual examples and comparison examples was evaluated according to JIS specification. The evaluation items are described below. The coated film obtained at the time of completion of the electodeposition coating was called the electrodeposition coated film and the coated film obtained at the time of completion of the topcoat application was called a 3-coat coated film.
- (i) Salt Spray Test: electrodeposition coated film
- (ii) Adherence Test: 3-coat coated film
A crosscut was made with the use of a sharp cutter on the electrodeposition coating plate. This plate was sprayed with 5% salt water for 720 hours (according to JIS-Z-2371). After spraying, the widths of the maximum swelling from both sides of the crosscut area were measured and evaluated according to the following evaluation standards:
A sharp cutter was used to make 6 cuts in both the vertical and horizontal directions at 2 mm interval on the 3-coat coated film to obtain 25 squares (according to JIS-K-5600-5-6). The squares were peeled off by a tape and evaluated by the evaluation method according to the aforementioned JIS specification.
The results of evaluation of the external appearances of test plates obtained from the actual examples and comparison examples and the adhering quantity of the surface coating film are summarized in Table 1 and Table 2. The SPC materials and EG materials obtained from the actual examples all gave a uniform film and the targeted film adhering quantity could be attained. In contrast, the deposition of a surface coating film could not be achieved on either the SPC materials or the EG materials obtained from Comparison Example 1 because of the small value of the total mass concentration ratio K1. Deposition of a surface coating film was also not possible on either the SPC material or the EG material obtained from Comparison Example 2 because of the small content of component (A). Deposition of a surface coating film was also not possible on either the SPC material or the EG material obtained from Comparison Example 3 because of the large value of the total mass concentration ratio K1 and the high free fluorine ion concentration D. Formation of a surface coating film was possible on the SPC material and the EG material obtained from Comparison Example 4 because a conventional zinc phosphate treatment was employed in this example.
Table 3 shows the results of coating performance evaluation of the electrodeposition-coated film. The SPC material and EG material obtained from the actual examples all showed excellent corrosion resistance. In contrast, the promoting effect of component (B) on the film formation of component (A) was not sufficient in Comparison Example 1 because of the small value of the total mass concentration ratio K1. Accordingly, there was not very much deposition of a surface coating film on either the SPC material or the EG material and the corrosion resistance of the deposited film was poor. For the SPC material and the EG material obtained from Comparison Example 2, the targeted adhering quantity could not be achieved and the corrosion resistance was poor because the content of component (A) was too low. For the SPC material and the EG material obtained from Comparison Example 3, the targeted adhering quantity could not be achieved and the corrosion resistance was poor because the total mass concentration ratio K1 was too large and the free fluorine ion concentration D was too high. In Comparison Example 4, a zinc phosphate treatment commonly used for cation electrodeposition coating was employed. The coating performances obtained from the actual examples were all superior to those obtained from Comparison Example 4 at all levels.
Table 4 shows the results of evaluation of the adherence property of the 3-coat plate. The adherence property with regard to all the test plates used in the actual examples was excellent. For the comparison examples, as in the case of the corrosion resistance of the electrodeposition coated plate, the adherence property with regard to the test plates used in all the comparison examples except for Comparison Example 4 was not as good as that obtained with the actual examples.
It can be seen from the results mentioned above that, with the use of the composition for surface treatment, the treatment liquid for surface treatment, the surface treatment method, and the surface treated metal material of the present invention, the deposition of a surface coating film with excellent adherence and excellent corrosion resistance becomes possible.
2.0 g/m2
4.2 g/m2
adhering quantity of zinc phosphate
[Table 4]
Evaluation According to JIS K-5600-5-6