Anticorrosive coating material and method of rust prevention

Details Anticorrosive coating material and method of rust prevention Anticorrosive coating material and method of rust prevention

2000-11-06

2003-08-19

Green, Anthony J. (Department: 1755)

Compositions: coating or plastic

Coating or plastic compositions

Corrosion inhibiting coating composition

C148S243000, C427S372200, C427S385500, C428S425800, C428S545000, C524S140000, C524S211000, C524S539000, C524S591000, C524S839000, C524S840000

Reexamination Certificate

active

06607587

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a surface treatment composition and a surface treatment for a metal material, a steel plated with a metal (referred to as a metal-plated steel hereinafter) or a non-plated steel, and provides an anticorrosive agent capable of imparting a sufficient corrosion resistance to a metal material.
BACKGROUND ART
A metal-plated steel undergoes the formation of white rusts on their surface in a salt-containing atmosphere such as a sea water or in a high-temperature/high humidity atmosphere, resulting in a markedly deteriorated appearance or a reduced anticorrosive ability of a substrate iron surface.
In order to prevent the formation of such white rusts, a chromate-based anticorrosive treatment agent has been employed, such as a resin-based treatment agent disclosed in Japanese Patent Application Laid-Open No. 3-131370, which contains a water-dispersible chrome compound and a water-dispersible silica in an olefin-&agr;, &bgr;-ethylenically unsaturated carboxylic acid copolymer resin dispersion.
However, a chromium-containing resin-based treatment agent described above dose not always exhibit a sufficient corrosion resistance, and undergoes the formation of the white rusts when exposed to a salty water or a high temperature/high humidity atmosphere for a prolonged period. Recently, a non-chromium anticorrosive treatment agent is desired increasingly.
We had discovered that a sulfide ion reacts with zinc to form a stable ZnS coating and had disclosed non-chromium anticorrosive treatment agents employing a sulfide and sulfur in Japanese Patent Application Laid-Open No. 8-239776 and No. 8-67834.
Nevertheless, some of the sulfides exhibit peculiar odors and are not always handled easily.
An anticorrosive treatment agent employing a triazinethiol compound which contains a sulfur atom but has no odor or toxicity was also proposed. For example, Japanese Patent Application Laid-Open No. 53-31737 titled “water-soluble anticorrosive paints” discloses a water-soluble anticorrosive paint containing a dithiol-S-triazine derivative.
Japanese Patent Application Laid-Open No. 61-223062 titled “Emulsions having reactivity with metals” discloses an emulsion having a reactivity with a metal obtained by mixing a thiocarbonyl group-containing compound and an organic compound which is hardly soluble or insoluble in water.
However, a water-soluble anticorrosive paint disclosed in Japanese Patent Application Laid-Open No. 53-31737 described above is intended to prevent the corrosion of a soft steel, copper, brass, a copper wire and the like, and is formulated so that it enables a tight contact especially when a substrate is a copper and a brass. Accordingly, it is not satisfactory when used as an anticorrosive agent for the surface of a metal such as zinc.
A reactive emulsion disclosed in Japanese Patent Application Laid-Open No. 61-223062 described above is not satisfactory either when used as an anticorrosive agent for the surface of a metal such as zinc, since it is also an emulsion which reacts with copper, nickel, tin, cobalt, aluminum and alloys thereof.
We made an effort in the studies on a triazinethiol-containing anticorrosive coatings which is useful also to prevent the corrosion of a zinc-based plated steel, and previously disclosed a triazinethiol-containing anticorrosive coatings described in Japanese Patent Application No. 9-2557. Nevertheless, since triazinethiol is an expensive compound, an anticorrosive treatment agent available at a further low cost is desired.
Examples of the method for the surface treatment of zinc or a zinc alloy employing no chromium or triazinethiol are those described in Japanese Patent Application Laid-Open No. 54-71734 and No. 3-226584. Japanese Patent Application Laid-Open No. 54-71734 provides a method for the surface treatment of zinc or a zinc alloy wherein the surface of said zinc or zinc alloy is treated with an aqueous solution containing 0.5 g to 100 g/L of a 2 to 6 myoinositol-bound phosphate or a salt thereof, 0.5 to 30 g/L as a metal of one or more substances selected from the group consisting of titanium fluorides and zirconium fluorides and 1 to 50 g/L of thiourea or its derivative. Since this method involves the formation of a passive coating as a protective layer on the zinc surface, it requires a titanium fluoride or a zirconium fluoride. Japanese Patent Application Laid-Open No. 3-226584 discloses a surface treatment agent which is an aqueous solution at pH 5 to 10 comprising 0.02 g/L or more of one or more of Ni
2+
and Co
2+
, ammonia and one or more primary amine group-containing compounds. Since this agent achieves the paint adhesiveness and the post-painting corrosion resistance as a result of the precipitation of cobalt or nickel, it requires Ni
2+
and/or Co
2+
. As described above, a treatment agent containing a metal ion involves problematic characteristics such as an increased load upon waste water disposal.
In order to solve the problems mentioned above, we disclosed in Japanese Patent Application Laid-Open No. 9-123813 aqueous resin-based non-chromium-based anticorrosive coatings which contain a thiocarbonyl group-containing compound and a phosphate ion. This anticorrosive coatings provide a further increased corrosion resistance when incorporated with a water-dispersible silica. This procedure is a chromium-free process and exhibits an excellent anticorrosive effect, but was proven to undergo the reduction in the storage stability when an increased amount of the water-dispersible silica is added.
DISCLOSURE OF THE INVENTION
An objective of the present invention, in view of the problems described above, is to provide non-chromium anticorrosive coatings effective for a metal material and has a corrosion resistance higher than that of a chromium-containing anticorrosive agent and which is less expensive, and a method for the anticorrosive treatment. Further the present invention provides an anticorrosive-treated metal material treated with non-chromium anticorrosive coatings which have an excellent corrosion resistance. The anticorrosive coatings of the present invention contain a compound containing a thiocarbonyl group and a water dispersible silica in an aqueous solution of a water soluble resin but not containing substantial amount of a phosphate ion.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention relates to anticorrosive coatings comprising, in 1 liter of a composition containing at least one of aqueous resins and water as main ingredients, 0.2 to 50 g of at least one of thiocarbonyl group-containing compounds and 50 to 500 g of a water-dispersible silica, without a substantial amount of phosphate ion.
Furthermore, an anticorrosive treatment of the present invention is a method of coating anticorrosive coatings described above onto a metal material.
In the present specification the term “metal material” includes a steel, titanium, aluminum, copper plate or the like and a metal material plated by galvanizing, fused metal plating and the like. As the steel a cold-rolled steel, a hot-rolled steel, a stainless steel and the like are exemplified.
In the present specification the term “plated-steel” means a steel which is plated with a metal such as Zn, Al, Ni, Cr, Sn, Pb, Fe and the like, or an alloy of the above metal and at least one of any other metals. Examples of the other metals include Co, Ni, Fe, Cr, Al, Mg, Sn, Mn, Zn, Ti and the like. A metal which is alloyed by a heat treatment after the plating is also included. A small amount of another metal such as Co, Mo, WNi, Ti, Cr, Al, Mn, Fe, Mg, Pb, Sb, Sn, Cu, Cd, As and the like as a hetero-metal or an impurity, and/or a metal material in which at least one of inorganic compounds such as silica, alumina, titania and the like are dispersed, or a plating containing any ingredients other than Fe—P. The plating may contain plural layers.
The method of plating may include electro-galvanizing, fused metal plating, deposition, injection and the like.
Furthermore, an anticorrosive-treated metal material accord

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