[0001] This invention relates to a method of a metal surface treatment.
[0002] Considerable problems have hitherto been experienced in effecting coating of some
materials including paints and some metals on metal surfaces.
[0003] As illustrative, but not limiting, enormous difficulty is experienced in attempting
to coat what is termed hard chrome onto a metal surface of another type for instance,
steel, and while it is capable of being achieved, in practice, it requires a number
of steps in an electroplating process which require both time and expertise in effecting.
[0004] In another application, it is known that it is very difficult to have a paint based
upon a resin, adhere to a zinc coated steel surface where this has been newly prepared.
[0005] Perhaps because the paint whether this is based on an acrylic resin or some differing
resin material requires a mechanical interlocking bond or not, it is conventionally
accepted that such paint should not be applied to a surface such as newly prepared
zinc coated steel until the coat has weathered, which may take some months or in some
cases, years.
[0006] In another instance, it is conventionally acknowledged that it is most difficult
to effect the coating either of another metal or a protective coating on an aluminium
surface.
[0007] It is now believed that this is because of the characteristic of the well acknowledged
oxide formed on the surface of the aluminium metal.
[0008] The above three illustrations indicate difficulties that have been experienced thus
far and are real problems in the art in relation to the coating of metal surfaces.
[0009] This invention is concerned with the treatment of metal surfaces including ferrous
and non-ferrous metals and alloys which assist in the subsequent bonding of surface
coatings and which incidentally assist in reducing vulnerability of the surface to
subsequent further oxidisation.
[0010] The invention involving the method uses a solution which is applied to the metal
surface and which is so compounded that it will provide a beneficial coating effect
in relation to metal surfaces which will provide a base upon which subsequent coating
can be more effective than has hitherto been the case, and in some instances enables
a coating that has hitherto not been able to be as effectively or economically enabled
to be secured to the surface of the said metal.
[0011] I have hitherto described a solution especially in relation to a preferred arrangement
which I found was suitable for application to corroded metal surfaces.
[0012] This invention relates to firstly a broadening of the general discovery of that first
invention and the discovery of its wider applicability to enable coating to be achieved
subsequently which has hitherto not been realized.
[0013] Conventionally, treatment of a metal surface has been based on the concept of removing
the oxidised surface which almost inevitably exists on the surface whether the metal
appears to be bright clean or badly corroded.
[0014] Treatment therefore has taken two main approaches that is, either to apply to the
surface a material which can substantially attack and thereby dissolve and remove
the metal oxides as well as the metal underlying the oxides on the basis that this
will remove any seat of corrosion or secondarily it relies upon the expectation of
most of the metal oxide to be physically removed and then to cover the surface with
a generally impermeable membrane which will therefore seal the surface from access
of water or other corrosion inducing materials.
[0015] From experiments conducted thus far, neither of the two conventional processes appear
to provide significant improvement and in a number of cases, according to experiments
conducted would appear to, at least in the long term, worsen the vulnerability of
the material to attack.
[0016] Typically, if steel is pickled by immersion in hydrochloric acid, besides the fact
that the surface can be irregularly corroded by the hydrochloric acid, the hydrochloric
acid in itself must subsequently be neutralized or removed by quenching and this in
itself leaves agents which can induce further oxidisation.
[0017] While an acid such as phosphoric acid can be used for pickling, it is seldom used
for scale removal because it is an expensive acid and slow in operation.
[0018] However, some steel plates are often initially de-scaled in sulphuric acid, and then,
after rinsing, immersed in a 2% phosphoric acid containing very small quantities of
iron and at a high temperature, such as 80-90°C. for several minutes.
[0019] This provides an iron phosphate coating which is considered useful for afterwards
coating with paint.
[0020] The difficulty with simply coating the material with a material that forms in effect
an impermeable membrane is the difficulty that it is almost impossible to ensure that
there is not a humid atmosphere between the membrane and the metal surface provided
either by the drying of the setting membrane or by entrapped air providing from time
to time condensed water or perhaps more commonly, the breakdown in the surface at
one or more places, and the subsequent ingestion between the commonly rather loosely
adhered membranes and the metal surface, thus allowing water not only to be pulled
into the interface but to be kept there because of the membrane and in fact therefore
promote corrosion.
[0021] The first discovery of this invention is that it is of significant value to apply
to the metal surface which will inevitably have oxide thereon upon any exposure to
air, a material which is formulated so that rather than attack the metal oxide. it
will have no or minimal reactivity with respect to the metal oxide and hence much
more readily than with other materials perfuse through the oxide without substantially
affecting this or blocking this porous character of the oxide by the reaction products
such as a gas or other materials.
[0022] The material however is selected or formulated so that when it reaches the base of
the oxide, it is reactive with respect to the metal providing the surface from which
the oxide is formed or perhaps in other words is substantially more reactive with
respect to the metal base than the oxides so that by applying such material to the
surface of a corroded material, the material will perfuse without significant reaction
through the pores of the oxide and then attack the meta; at the base releasing or
lifting off the oxides.
[0023] The next discovery of this invention relates to the problem of limiting the corrosion
and providing a further base upon which subsequent coating can be effective.
[0024] By including in the formulation, materials with significant concentrations having
large molecular weights, it has been found that this material can confine the acid
attack or the base attack so that firstly the rate of reaction is limited so that
the release of gas is at a limited rate but at the same time, the reaction products
are held within the vicinity of the area of reaction so that by including metal iron
in the solution, especially those at a higher position in the electromotive series,
then with the acid or base attack occurring, the reaction products will be taken into
the solution with the result displacement potential of these other metals and these
are very likely to form a strong attachment bond with the then accessible metal bonds
forming the base or insofar that there are complex molecules in the solution, there
is a high likelihood of forming complex association bonds at or around the site of
the reaction.
[0025] The characteristics of the solution then provide also in effect, protection from
oxidation of the metal being exposed by the acid or base attack.
[0026] By then treating the thus prepared surface in such a way as to induce further coating
either by metal buildup or by reason of organic or inorganic coating materials and
in such a way as to be able to accept within the coating method the presence of the
said solution or in another way neutralising this, one can then obtain a coating on
metals in such a way and with materials that have not hitherto been able to be so
combined, or so economically combined.
[0027] The invention can in one form then be said to reside in a method of treatment of
a metal surface including the steps of preparing the surface and then building up
a protective coating on the metal surface so prepared, the preparation of the surface
including the step of applying to the surface a solution formulated or selected so
as to be substantially non-reactive with any oxide of the metal surface, adapted to
perfuse through any oxides on the surface of the metals insofar that these are porous
without thereby being blocked by reaction products, and then adapted to react with
the underlying metal providing the metal surface, and then to cover such underlying
metal so as to allow ion exchange between metal ions such as those of higher electromotive
series with respect to the metal of the surface and those in the formulation of the
solution and the metal of the surface but to substantially resist access to the metals
or gas so as to significantly retard any formation of oxides of the metal forming
the surface, and then applying compatible coating materials either by way of electro-deposition
or otherwise onto the thus prepared surface.
[0028] It is to be emphasized that the results of the preparation appear to produce a surface
which does not appear to have previously been provided and its compatibility to subsequent
coating either by way of electro-deposition or to coating by applying a painting solution
or otherwise is also a significant discovery in that the prepared surface appears
to provide significant molecular bonding so that there is a better grip and therefore
a potential for applying metals by way of electro-deposition that could not previously
be applied with effective grip hitherto, and similarly with painting solutions, provided
these are compatible with the solution that will to a certain extent be left on the
surface, then there can also be a significant increase in bonding attachment.
[0029] The process therefore appears to have the joint advantage that it will not only not
depend upon having to physically remove rust or to provide a first attack of a very
strong acid with subsequent necessary treatments but of course with a single application
being available and with the necessity of removal not being any longer present, a
number of materials can be treated in situ and of course within a short period of
time can be immediately coated withcut significant disadvantage by reason of underlying
great rust or other oxide potential.
[0030] The concept then is to formulate the solution and treat the surface so that in fact
quite contrary to what has been the conventional concept, the oxide of the metal is
not attacked and it is the concept that one should arrange the formulation that there
is most decidedly preferrential attack to the base metal so that access to the base
metal is not impeded by any reaction with the oxides this of course assuming as has
been discovered by experiment that all of the oxides of metal forming on the surface
in a corrosion type situation appear to be porous and of course that the formulation
is suitable for the selected metal and the oxide in question. There is also an assumption
that the formulation will wet the oxides and if this is not generally possible, additional
material such as appropriate surfactants may be necessary to assist such wetting and
therefore perfusion of the formulation through the oxides.
[0031] An understanding of the action is perhaps better achieved by reference to a preferred
formulation which also happens to be useful for a number of metals with their oxides
on their surface.
[0032] The preferred formulation also perhaps surprisingly, has materials which individually
provide a single function or a multiplicity of functions but it is well understood
that such functions can be provided by two or more materials acting in concert.
[0033] The reference to the preferred formulation then is not to be taken as necessarily
limiting the applicability of the method to such formulation although the components
of the formulation have provided significant advantages but clearly many other formulations,
once the underlying concept of the method has been realized, can be devised to provide
the same function and significant advantages.
[0034] According to the preferred solution then, this includes a acid and preferably also
phosphoric acid H
3P0
4 produced from commercial acid of 82% H
3PO
4 known as syrupy nhosphoric acid. Because orthophosphoric acid is a triprotic acid,
it forms three series of salts corresponding to three stages of ionisation. The primary
phosphates are mote soluable in water than tertiary phosphates.
[0035] The solution also contains a significant proportion of urea. Typically a mixture
of 82% orthophosphoric acid, mixed with an aqueous solution of urea in the proportions
- one part by weight of urea, to two parts by weight of the phosphoric acid solution
- produces a crystalline addition product which is strongly acid and which is soluable
in water. In the solution preferred in the embodiment, there is an excess of phosphoric
acid over that which is required to produce this addition product.
[0036] The preferred solution also contains significant amounts of the sulphates of copper,
nickel, chromium,manganese, cobalt, and in some cases zinc. These can have several
functions, one of which is to act as an activator in assisting the attacking or underlying
metal providing the metal surface and they also of course provide for sequential deposition
of the metal on the surface and subsequent passivating of the surface.
[0037] The depositions also include phosphates which are of course formed when this preferred
solution is formed which grow on the phosphate ion primary layer.
[0038] Typically then, when the preferred solution is applied to a metal surface such as
iron, the metals in the solution, for example copper, being cathodic to the dissolving
iron, increase the rate of solution of iron by depositing on the iron and forming
local cells with it. Thus a large number of centres for crystal growth are produced
which result in rapid formation of phosphate coating.
[0039] In a preferred instance then, a copper film is formed in relation to a still surface
with the copper film being uniformly adherent when the preferred solution is applied
by wiping, or if the surface temperature of the steel is raised to about 80°C. For
the later building up of the coat, the steel sheet is then immersed after draining
in either nickel sulphate or chromium sulphate for several minutes so that nickel
or chromium phosphaue is deposited on the iron phosphate underlayer and finally there
becomes a layer of pure nickel or chromium phosphate.
[0040] The term phosphate is given as a simple terminology reference but of course, especially
with the urea present, there would be a mixed phosphate with the crystalline addition
product of urea and orthophosphoric acid. An absorption barrier is accordingly formed
in the unrusted areas of the specimen by the urea phosphoric acid complex and there
is of course a lower reaction rate than that of the solution absorbed into the rust.
[0041] In the metal oxide, autophoretic or electrophoretic separation of the excess phosphoric
from the completed reaction appears to occur, accelerating attack on the underlying
iron compared with the unoxidized areas providing a reservoir of acid.
[0042] The action of the urea therefore can be likened to an inhibitor, but it also has
additional characteristics which are of significant advantage in the method.
[0043] A first of these is that it assists in wetting of oxidized metal surfaces and it
has a characteristic perhaps termed an ability to creep over surfaces which has been
suggested as being caused by an ability to crystallize and recrystallize at its edges,
thereby achieving this creeping feature.
[0044] Another advantageous feature is the character of the combination of urea and phosphoric
acid and also another feature is the fact that it provides especially in the higher
concentrations at the metal face, this more viscous layer which significantly inhibits
the action which firstly reduces the size of any gas bubble evolution which means
that the action is much more uniform over the whole of the surface and the effect
appears to be somewhat akin to a micro-etch rather than a macro-etch or significant
pitting and it also appears to provide an association complex with the materials at
the reacting face which is substantially insoluble subsequently but provides a good
binder for subsequent coating. It is also useful because it will be compatible when
used as a complex associating molecule with subsequent electroplating techniques.
[0045] Reference has been made to the applications to especially steel surfaces, but it
is to be understood that it would appear that the concept applies to any metal surface.
[0046] As illistrative, aluminium alloy is very suitable for this treatment, and as with
steel, an aluminium alloy should be appropriately degreased by application of appropriate
solvents which allow for removal of fatty compounds that are typically'found on the
surface of metals.
[0047] With relation to the preferred solution, an aluminium part, if heated to approximately
90°C and then immersed in the preferred solution for approximately 5 minutes, will
have significantly corrosion products removed and there will be observed a minor etching.
[0048] With the preferred solution, a copper deposit will be noticed on the surface of the
aluminium in a friable form. This can be simply removed by washing and scrubbing the
surface leaving a clean aluminium surface but preferably in relation to this invention,
the part can be immediately plated in copper, nickel or chromium plating baths,-leaving
the copper. The copper will be replaced in the action but it provides a good basis
upon which the action can proceed.
[0049] A selection of the various compounds or materials forming the solution will depend
upon many factors including effectiveness in relation to the material to be used,
the costing, safety of usage and of course the long term effectiveness of the answer
provided.
[0050] It is appreciated that there are many combinations of solutions that would be suitable
and that at least in the wider concept of this invention, it is the discovery of the
mechanism so that compounds can be effectively formulated and when applied, can be
understood as to provide a useful basis for subsequent coating.
[0051] The preferred solution has significant advantages in sofar that with relatively safe
materials from a toxicity point of view and from a cost point of view, a solution
which is relatively simple and economic can be widely used in relation to a large
variety of metal surfaces.
[0052] It is to be emphasized however, that this is realized as being typical and not limited
to the inventive concept at least in its wider concept.
[0053] Typically then, acids or bases with relatively weak dissociation constants may be
used in a formulation either with or in replacement of phosphoric acid typically a
dissociation constant of 7.5 x 10
-3 or as in the case of ascetic acid 1.8 x 10
-5 or in the case of formic acid 1.8 x 10
4 all could be suitable.
[0054] Typically, other acids that are considered useful provided the other formulation
aspects are satisfactory, can include oxalic acid, carbonic acid, hydrogen selenide,
hydrofluoric acid and so on.
[0055] Typically, bases can also be used including ammonia, dymethylamine, methylamine,
trimethylamine and the like.
[0056] It is significant that as well as a weakly dissociated acid or base, there needs
to be a significant concentration of a material which conventionally can be useful
as an inhibitor.
[0057] It is to be emphasized that the action is not only an inhibitor in this application,
but it is a name used to indicate the type of material suitable in this case.
[0058] Large molecules such as the polysaccharides or urea or substituted ureas, amides,
thiourea and substituted thioureas may also be suitable.
[0059] This of course is not to suggest a limitation to the scope but simply to indicate
an illustrative example of type of molecule and the fact that a significant concentration
will firstly assist to inhibit the acid action on the oxide of the metal, assisting
hopefully in also perfusing through the oxide to the underlying metal and then assisting
firstly in the limiting of the reaction base and access of oxide forming materials
from externally and finally, being either compatible with or forming an association
complex with the underlying metal in combination with other portions of the compound
provided.
[0060] Finally, it is a necessary feature to assist in the later passivation that there
be metal ions provided in the material and typically these are transitional elements
sulphates.
[0061] Once again however, this is illustrative in that the sulphates are generally water
soluable and we have been talking generally of aqueous solutions and also that these
salts are more economic than others which are also water soluable.
[0062] Having now described in general terms aspects of the invention, the invention will
be better understood with reference to examples which shall now be given, of the way
the invention wan be preferrably carried out.
[0063] The composition and preparation of the solution used in the first application to
the metal surface in one preferred form is as follows:
Four hundred grams dry urea (46%N 0.4 biuret) is dissolved in 1600 millilitres of
hot water (85°C) and to this is added 200 millilitres of a sulphate solution, this
being made by dissolving 40 grams of each of the following metal sulphates in 1140
millilitres of water - these sulphates being Copper Sulphate, Cobalt Sulphate, Chromium
Sulphate, Nickel Sulphate, Manganese Sulphate and Zinc Sulphate -- and to this mixture
adding 3200 millilitres of phosphoric acid 82% technical grade.
[0064] This provides approximately 5 litres of the solution.
[0065] The above solution contains by weight then:
[0066] In the forthcoming examples this solution will be referred to as the solution of
the preferred embodiment of the invention.
EXAMPLE 1
[0067] The metal article to be plated may first be cleaned to remove grease, oil, and loose
solids by any of the common methods such as solvent cleaning, emulsion cleaning or
alkaline cleaning. Where mill scale and rust are present, it is of course feasible
to use weathering and wire brushing, acid pickling, grit blasting or flame cleaning.
In the present invention it is found that new steel may be cleaned with solvent such
as perchlorethylene 80% and butanol 20% by weight, or methyl ethyl ketone, particularly
if the initial temperature of the specimen is for example from 20°C - 100°C. Adequate
cleaning may be given by immersing the specimen in the solution of the preferred embodiment
of the invention at temperatures of 40°C - 100°C for times depending on the temperature
but generally of the order of 10 seconds to 1 minute at 100°C. If the specimen is
heated to 100°C - 140°C first and dipped in the solution of the preferred embodiment
of the invention a cloud of fine bubbles emanates from the specimen and indicates
that micro-etching has occurred. and the surface is ready for further treatment.
[0068] The article may then be placed in the selected electroplating bath, for example a
copper plating bath comprising:
[0069] Operating conditions:
50 - 70°C, 2-6 amps per dm , 2 - 6 volts, pH 12.2 - 12.8, current efficiency 50 -
60%, anodes copper rolled and annealed, steel vat, free cyanide 3 - 6 grams per litre.
[0070] Or the article may be placed in a selected electroplating bath for example a chromium
plating bath comprising:
[0071] The solution should be boiled with citric acid 12.5 grams per litre, tartaric acid
18 grams per litre or oxalic acid 25 grams per litre to give some reduction. The operating
conditions are, 40 - 50°C 12 - 20 amps per dm
2, current efficiency 12 - 15%, volts 4 - 5, 7% antimonial lead anodes, in a vat made
of steel, lined with 7% antimonial lead.
EXAMPLE 2
[0072] Where the metal article to be heated is zinc or zinc based alloys such as used in
diecastings, the application of the solution of the preferred embodiment of the invention
may be carried out by brushing, spraying or immersion. As the solution rate for the
zinc is much higher than that for steel, temperatures and times of immersion are reduced
to prevent undue etching of the surface, for example at 40°C, 5 - 10 seconds may be
adequate. The copper plating bath shown in example 1 is recommended for zinc and zinc
based diecastings; the pH value should be controlled by adding sodium hydroxide if
it is too low, tartaric acid if it is too high.
[0073] A chromium plating solution for direct plating on the zinc and zinc based diecastings
is as follows:
[0074] Operating conditions:
15 - 21°C, current density 100 amps per dm2, 6 - 12 volts.
EXAMPLE 3
[0075] When the metal article to be heated is aluminium or aluminium alloys, as in sheet
or castings, the application of the solution of the preferred embodiment of present
invention to the article is best achieved at temperatures in the range of 20°C - 40
0C and the progress of treatment can be gauged by the appearance of a friable thin film
of copper on the specimen.
[0076] The specimen can then be transferred to a copper plating solution such as alkaline
copper of composition:
[0077] Operating conditions:
20 C, 0.3 - 0.6 amps per dm , copper anodes, vat: earthenware or polymer lined.
[0078] Or transferred direct to a chromium plating solution such as that in example 1.
[0079] Or transferred to an autocatalytic copper plating that is current-less bath such
as that proposed by A.E. Cahill in U.S. Patent 2,874,072 (1959).
[0080] For example a solution could be:
[0081] Or transferred to a zincate solution containing 525 grams of sodium hydroxide and
100 grams of zinc oxide per litre and immersed for 1 - 3 minutes at 20°C, rinsed and
copper plated in the previously mentioned copper baths, followed by plating with hard
chromium from solution as in example 1.
EXAMPLE 4
[0082] Treatment of the metal articles with the solution of the preferred embodiment of
the invention is followed by dipping in a concentrated solution of metal sulphate
or phosphate at 40 - 100°C for 5 seconds - 1 minute at 100°C, which produces a metal
phosphate coating such as chromium phosphate. A suitable solution is for example:
[0083] A further solution is for example:
EXAMPLE 5
[0084] In example 4, metal sulphates or phosphates are used such as cobalt, nickle, manganese,
silver, gold, platinum and zinc.
EXAMPLE 6
[0085] This example involves the direct plating in a single solution of copper onto a metal
in single stage process.
[0086] A suitable solution is as follows:
[0087] The copper sulphate may be replaced by nickel, cobalt, manganese, zinc, silver or
gold, or by chromic acid to directly plate these metals onto a metal surface.
EXAMPLE 7
[0088] The solution of the preferred embodiment of the invention is used to prepare the
surface of aluminium alloy castings for hard chrome plating from a normal plating
solution of chromic acid 250 grams per litre, sulphuric acid 25 grams per litre and
is operated at 300 amps per square foot at 4 - 8 volts.
[0089] These examples are by way of illustration only and are not intended to limit the
invention.
1. A method of treatment of a metal surface including the steps of preparing the surface
and then building up a protective coating on the metal surface so prepared, the preparation
of the surface including the step of applying to the surface a solution formulated
or selected so as to be substantially non-reactive with any oxide of the metal surface,
adapted to perfuse through any oxides on the surface of the metals insofar that these
are porous withcut thereby being blocked by reaction products, and then adapted to
react with the underlying metal providing the metal surface, and then to cover such
underlying metal so as to allow ion exchange between metal ions such as those of higher
electromotive series with respect to the metal of the surface and those in the formulation
of the solution and the metal of the surface but to substantially resist access to
the metals or gasses so as to significantly retard any formation of oxides of the
metal forming the surface, and then applying compatible coating materials either by
way of electro-deposition or otherwise onto the thus prepared surface.
2. A method of metal surface treatment as in Claim 1 wherein said solution includes:
(1) a weak acid or weak base,
(2) an inhibitor, and '
(3) salts of one or more transition metals
the acid or base having the characteristic that the acid or base will not substantially
react with the oxides of the metal comprising the metal surface but will react with
the unoxidised metal of the metal surface,
the inhibitor being selected to limit substantially the rate of reaction of the acid
with the unoxidized metal, and to provide a buffering action of the acid in the said
solution, and further to at least substantially limit gaseous effusion and hence limiting
access of further solution to the metal surface, and
the concentration and types of the said acid or base, inhibitor and metal salts being
further selected such that at least after an initial reaction with the base metal
surface there is a bonding of the metal of the one or more of the metal salts in solution
with the unoxidized metal surface as a complex.
3. A method of metal surface treatment as in Claim 2 wherein the weak acid is selected
from a group comprising phosphoric acid, acetic acid, tartaric acid, citric acid,
succinic acid, malaeic acid, tannic acid and formic acid.
4. The method of metal surface treatment as in Claim 2 wherein the weak base is selected
from the group comprising ammonia, methylamine, dimethylamine and trimethylamine.
5. A method of metal surface treatment as in either of the preceding claims in which
the inhibitor is selected from a group comprising urea and substituted ureas, amides,
thiourea and substituted thioureas, and polysaccharides.
6. A method of metal surface treatment as in any one of Claims 2 to 6 wherein the
metal salts are selected from a group comprising cobalt sulphate, copper sulphate,
nickel sulphate, chromium sulphate, zinc sulphate, or manganese sulphate.
7. A method of metal surface treatment as in Claim 2 in which the acid is phosphoric
acid and the inhibitor is urea and the proportions by weight are within the range
of approximately 5 - 15% by weight of urea as compared to the weight of phosphoric
acid.
8. A method of metal surface treatment as in any one of Claims 2 to 7 in which the
concentration of metals salts is in the range of 0.5 - 1.5% by weight as compared
to the weight of phosphoric acid.
9. A method of metal surface treatment as in any one of the preceding claims in which
said compatible coating is applied by means of a chemical plating solution to thereby
deposit a metal coat onto the thus prepared surface.
10. A method of metal surface treatment as in any one of the preceding claims in which
said compatible coating solution is applied by means of an electroplating solution
and the method includes the further step of applying an electric current to thereby
obtain the deposition of a metal coat onto the thus prepared surface.
11. A method of metal surface treatment as in any preceding claim in which said compatible
coating is applied by means of a solution of polymeric resins and pigments in a solvent
and said coating material is a paint.
12. The method of treatment of a metal surface which includes the steps of applying
to the surface a solution including phosphoric acid, urea, and one or more soluble
metal salts selected from the salts of the metals chromium, cobalt, copper, nickel,
zinc and manganese and then applying, either with the said solution or with a further
solution, to the thus prepared surface, coating materials applied either by way of
electro-deposition or otherwise onto the thus prepared surface.
13. The method of treatment of a metal surface as in Claim 12 in which the urea is
present in a concentration of from 5 - 15%,by weight compared to the weight of phosphoric
acid.
14. The method of treatment of a metal surface as in Claim 12 in which the concentration
of phosphoric acid is the range of 40 - 75% by weight as compared to the weight of
the solution.
15. The method of treatment of a metal surface as in any one of Claims 12, 13 or 14
in which the further application comprises the use of a chemical plating solution
to thereby deposit a metal coat onto the thus prepared surface.
16. The method of treatment of a metal surface as in any one of Claims 12, 13 or 14
in which the further application comprises the use of an electroplating solution and
further applying an electric current to thereby obtain the deposition of a metal coat
onto the thus prepared surface.
17. The method of treatment of a metal surface as in any one of Claims 12, 13 or 14
in which the further application comprises the use of solution of a polymeric resin
and pigments in a solvent and said coating material is a paint.