MY111371A - Non-chromated oxide coating for aluminum substrates. - Google Patents

Abstract

(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 CONTAINING A SOLUBLE COBALT-III HEXAVALENT COMPLEX, THE CONCENTRATION OF THE COBALT-III HEXAVALENT COMPLEZ BEING FROM ABOUT 0.01 MOLE PER LITER SOLUTION TO THE SOLUBILITY LIMIT OF THE COBALT-III HEXAVALENT 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 CD PLATED, ZN PLATED, ZN-NI PLATED, AND STEEL. THE COBALT-III HEXAVALENT COMPLEX MAY BE PRESENT IN THE FORM OF MEM[CO(R)6]N, WHEREIN ME IS NA, LI, K, CA, ZN, MG, OR MN, AND WHEREIN M IS 2 OR 3, N IS 1 OR 2, AND R IS A CARBOXYLATE HAVING FROM 1 TO 5 C ATOMS. (B)A CHEMICAL CONVERSION COATING SOLUTION FOR PRODUCING THE COBALT CONVERSION COATING ON A METAL SUBTRATE, THE SOLUTION INCLUDING AN AQUEOUS SOLUTION CONTAINING A SOLUBLE COBALT-III HEXAVALENT COMPLEX, THE CONCENTRATION OF THE COBALT-III HEXAVALENT BEING FROM ABOUT 0.01 MOLE PER LITER OF SOLUTION LIMIT OF THE COBALT-III HEXAVALENT COMPLEX. (C)A COATED ARTICLE EXHIBITING ACCEPTABLE 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 A12O3 AS THE LARGEST VOLUME PERCENT, AND COBALT OXIDES COO, CO2O3, AND CO3O4.