EP 0488430 B1 19970611 - Non-chromated cobalt conversion coating
Title (en)
Non-chromated cobalt conversion coating
Title (de)
Chromatfreier Kobalt-Konversionsüberzug
Title (fr)
Revêtement de conversion au cobalt, sans chromate
Publication
Application
Priority
US 62113290 A 19901130
Abstract (en)
[origin: EP0488430A2] (A.) A process for forming a cobalt conversion coating on a metal substrate, thereby imparting corrosion resistance and paint adhesion properties. The invention was developed as a replacement for the prior art chromic acid process. The process includes the steps of: (a) providing a cobalt conversion solution comprising an aqueous solution having a pH of about 7.0 to 7.2 and containing a soluble cobalt-III hexacoordinated complex, the concentration of the cobalt-III hexacoordinated complex being from about 0.1 mole per gallon of solution to the saturation limit of the cobalt-III hexacoordinated complex; and (b) contacting the substrate with the solution for a sufficient amount of time, whereby the cobalt conversion coating is formed. The substrate may be aluminum or aluminum alloy, as well as magnesium and its alloys, Cd plated substrates, and Zn plated substrates. The cobalt-III hexacoordinated complex may be present in the form of Me3[Co(NO2)6] wherein Me is one or more of Na, K, and Li. (B.) A chemical conversion coating solution for producing the cobalt conversion coating on a metal substrate, the solution being an aqueous solution having a pH of about 7.0 to 7.2 and containing a soluble cobalt-III hexacoordinated complex, the concentration of the cobalt-III hexacoordinated complex being from about 0.1 mole per gallon of solution to the saturation limit of the cobalt-III hexacoordinated complex. The cobalt conversion solution may be prepared by a bath makeup sequence including the steps of: (a) dissolving a metal nitrite salt; (b) dissolving an accelerator such as NaI; (c) dissolving a cobalt-II salt; and (d) then adding an oxidizer such as H2O2. (C.) A coated article exhibiting corrosion resistance and paint adhesion properties, the article including: (a) a metal substrate; and (b) a cobalt conversion coating formed on the substrate, the cobalt conversion coating including aluminum oxide Al2O3 as the largest volume percent, and cobalt oxides CoO, Co3O4, and Co2O3. <IMAGE>
IPC 1-7
IPC 8 full level
C23C 22/05 (2006.01); C23C 22/56 (2006.01); C23C 22/57 (2006.01); C23C 22/58 (2006.01); C23C 22/68 (2006.01); C23C 22/70 (2006.01); C23C 22/83 (2006.01)
CPC (source: EP)
C23C 22/68 (2013.01); C23C 22/83 (2013.01)
Designated contracting state (EPC)
AT BE CH DE DK ES FR GB GR IT LI LU NL SE
DOCDB simple family (publication)
EP 0488430 A2 19920603; EP 0488430 A3 19921216; EP 0488430 B1 19970611; AT E154401 T1 19970615; AU 650494 B2 19940623; AU 8822591 A 19920604; BR 9105184 A 19920721; CA 2056159 A1 19920531; CA 2056159 C 20010703; DE 69126507 D1 19970717; DE 69126507 T2 19970925; DK 0488430 T3 19980105; ES 2104655 T3 19971016; GR 3024046 T3 19971031; HK 1006861 A1 19990319; JP 3194607 B2 20010730; JP H059745 A 19930119; MX 9102254 A 19920601; NZ 240779 A 19941125
DOCDB simple family (application)
EP 91202181 A 19910827; AT 91202181 T 19910827; AU 8822591 A 19911127; BR 9105184 A 19911128; CA 2056159 A 19911125; DE 69126507 T 19910827; DK 91202181 T 19910827; ES 91202181 T 19910827; GR 970401701 T 19970709; HK 98105956 A 19980622; JP 31608191 A 19911129; MX 9102254 A 19911128; NZ 24077991 A 19911128