Corrosion prevention method for aluminum-based metal component, and corrosion-proof aluminum-based metal product produced by the method

Abstract

The present invention provides a corrosion prevention method for an aluminum-based metal component, which makes it easy to check the presence or absence of, a chemically formed film on the component, and a corrosion-proof aluminum-based metal product produced by the method. In the method, the following treatment agent (A) is brought into contact with a surface of the aluminum-based metal component to chemically form the following film (B) on the surface of the aluminum-based metal component: (A) a treatment agent comprising an aqueous solution of zinc sulfate, an aqueous solution of ammonium fluoride and an aqueous solution of sodium molybdate which are mixed together;(B) a chemically formed film (B) comprising zinc fluoride, molybdenum and aluminum fluoride. Thus, the corrosion-proof aluminum-based metal product is produced.

Description

Claims

1. A method of preventing corrosion of an aluminum-based metal component made of aluminum or an aluminum alloy, the method comprising: bringing a treatment agent (A) into contact with a surface of the aluminum-based metal component to chemically form a film (B) on the surface of the aluminum-based metal component;the treatment agent (A) comprising an aqueous solution of zinc sulfate, an aqueous solution of ammonium fluoride and an aqueous solution of sodium molybdate which are mixed together;the chemically formed film (B) comprising zinc fluoride, molybdenum and aluminum fluoride.

2. A method as set forth in claim 1, wherein the treatment agent (A) contains 5.25 to 26.25 g/liter of zinc sulfate heptahydrate, 1.5 to 4.5 g/liter of ammonium fluoride, and 0.5 to 2.5 g/liter of sodium molybdate dihydrate.

3. A method as set forth in claim 1, wherein the treatment agent (A) comprises the following zinc sulfate aqueous solution (a), the following ammonium fluoride aqueous solution (b) and the following sodium molybdate aqueous solution (c) which are mixed in a mass ratio of (a)/(b)/(c)=7/3/2:(a) an aqueous solution containing 15% by weight of zinc sulfate heptahydrate;(b) an aqueous solution containing 10% by weight of ammonium fluoride; and(c) an aqueous solution containing 5% by weight of sodium molybdate dihydrate, wherein zinc of zinc fluoride, molybdenum and aluminum of aluminum fluoride are present in the chemically formed film (B) in a content ratio of zinc/molybdenum/aluminum=5/4/1 on a mass basis.

4. A method as set forth in claim 3, wherein the treatment agent (A) having a mass ratio of (a)/(b)/(c)=7/3/2 comprises 35 to 175 g of the solution (a), 15 to 45 g of the solution (b) and 10 to 50 g of the solution (c).

5. A method as set forth in claim 1, wherein the treatment agent (A) has a temperature of 45 to 65° C. and the surface of the aluminum-based metal component is kept in contact with the treatment agent (A) for a period of 1 to 10 minutes.

6. A corrosion-proof aluminum-based metal product comprising: an aluminum-based metal component made of aluminum or an aluminum alloy; anda film (B) chemically formed on a surface of the aluminum-based metal component by a method as recited in claim 1, the film (B) comprising zinc fluoride, molybdenum and aluminum fluoride.

7. A corrosion-proof aluminum-based metal product as set forth in claim 6, wherein zinc of zinc fluoride, molybdenum and aluminum of aluminum fluoride are present in the chemically formed film (B) in a content ratio of zinc/molybdenum/aluminum=5/4/1 on a mass basis.