Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Patent
1992-07-28
1994-06-07
Silverberg, Sam
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
148273, C23C 1846
Patent
active
053186400
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to treating the surface of zinc coated steel, particularly sheet steel, e.g., electrogalvanized, electrolytic zinc-alloy plated, hot-dip galvanized, galvannealed, and/or zinc/aluminum alloy-plated steel, in order to deposit thereon nickel, cobalt, and/or compounds thereof, with the object of providing a surface which is an excellent underlayer for such subsequent coating operations as painting, laminating, ceramic coating, and the like. In concrete terms, the present invention is especially suited for the production of surface treated steel sheets (for example, painted steel sheet, laminated steel sheet, and surface treated car body panels) by coating or laminating either immediately after execution of treatment according to the present invention or after an intermediate chromating treatment or phosphating treatment.
BACKGROUND ART
It has long been known that the paint adhesion and post-coating corrosion resistance can be improved through chemical treatments in which a heavy metal and/or compound thereof is deposited on the surface of zinc coated steel sheet. Examples from the art in this regard are (1) Japanese Patent Publication Number 52-22618 (22,618/77] and (2) Japanese Patent Publication Number 43-12974 [12,974/68]. Both of these concern the deposition of a heavy metal, such as nickel, cobalt, iron, or the like, onto galvanized steel sheet. Heavy metal or oxide thereof is deposited onto zinc coated steel sheet by treatment in the acidic range at pH 2 according to the invention of reference (1) and by treatment in the alkaline range at a pH of at least 11 according to the invention of reference (2). A disadvantage accruing to each of these prior art references is the occurrence of excessive etching of the zinc (an amphoteric metal) by the H.sup.+ ion or OH.sup.- ion. This results in a degradation in the performance of the end product, for example, a decline in corrosion resistance.
Thus, methods are already known for improving the adhesion of coatings (e. g., paints, laminates, ceramic coatings, etc.) to the substrate through the substitution precipitation of cobalt or nickel onto zinc coated steel sheet, but in each case the prior treatment solution, being acidic or alkaline, etches the zinc substrate too much, with a resulting decline in performance, for example, in corrosion resistance. On the other hand, while excessive etching does not occur in the neutral pH region, the corresponding rate of metal substitution precipitation is so slow as to be useless for practical applications.
DESCRIPTION OF THE INVENTION
Problem to Be Solved by the Invention
The principal goal of the invention is the development of a nickel and/or cobalt deposition process which could be run at a nearly neutral pH but which would nevertheless be rapid, which deposits nickel and/or cobalt in quantities large enough to improve the paint adhesion and post coating corrosion resistance, and which has a good solution stability.
SUMMARY OF THE INVENTION
It was discovered that one or more compounds selected from among ammonia and amine compounds which carry at least one amino group, or preferably at least two amino groups, constitute an excellent complexing agent for the substitution precipitation of nickel and/or cobalt from a treatment solution in the neutral region. Said complexing agents have a good stability with metal ion in the neutral region and support the rapid deposition of quantities sufficient to improve the paint adhesion and post coating corrosion resistance. Examples of amine compounds which carry at least one amino group are: ethylenediamine, triethylenediamine, N-methylenediamine, N-n-propylethylenediamine, N,N-dipropylethylenediamine, 1,2-diaminopropane, meso-2,3-diaminobutane, meso-2,3-diaminobutane, cis-2,3-diaminocyclohexane, trans-1,2-diaminocyclohexane, trans-1,2-diaminocycloheptane, diethylenetriamine, triethylinetetramine, and various amino acids.
The substitution precipitation reaction of nickel and cobalt is substantially accelerated by the presenc
Ishii Hitoshii
Miyawaki Toshi
Mori Kazuhiko
Shima Shizuo
Henkel Corporation
Jaeschke Wayne C.
Silverberg Sam
Szoke Ernest G.
Wisdom, Jr. Norvell E.
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