FR2609725A1 - Aqueous solution for the treatment of chemical conversion of titanium or of its alloys - Google Patents

Abstract

The aqueous coating solution, at pH 1.5-4.5, containing fluoride ions and one or more metal ions chosen from Mg, Ca, Mn, Fe, Co, Ni, Zn and Mo, is characterised according to the invention in that the said aqueous solution for chemical treatment has added to it selectively one or more compounds chosen from an organic chelating agent (added quantity: 0.1-2 g/litre), an organic compound of high molecular weight, soluble in water (added quantity 0.1-10 g/litre) and a surface-active agent (added quantity: 0.01-3 g/litre). Metal treatment.

Description

The present invention relates to an aqueous coating solution for the formation of a chemical conversion layer on titanium or an alloy thereof used to form a metal fluoride film selected from
Mg, Ca, Mn, Fe, Co, Ni, Zn and Mo on said surface of titanium or one of its alloys, to improve lubrication during the cold forming process.

The fluoride coating of titanium borofluoride, titanium silicofluoride or the like is well known as a lubricant coating for the cold deformation of titanium or its alloys. However, this coating is thin, not very resistant, and its adhesion is also insufficient. Such disadvantages can be overcome by deposition of a chemical conversion layer consisting of a metal fluoride such as a fluoride of Mn, Mo, Mg, Ca, Fe, Co,
Ni and Zn, applied in addition to the aforementioned titanium fluorides.

 Japanese Patent Publication No. 28967/1969 gives examples of the conversion layer deposition solution used to obtain a coating film of this type.

The conversion layer deposition solution consists of an aqueous solution at pH 1.5-4.5, containing 5-40 g / liter of fluoride ion and 0.1-5 g / liter of metal ions, selected from Mn, Mo, Zn, Mg, Ca, Fe, Co and Ni.

 The fluoride ion contained in this aqueous solution for depositing a conversion layer may be introduced into this solution by adding hydrofluoric acid, borofluoric acid, silicofluoric acid or an alkali metal salt or ammonium of these acids. The metal ion can be introduced into this solution by addition of a nitrate, sulfate, chloride, fluoride, oxide, etc. of a metal selected from Mn, Mo, Zn, Mg, Ca, Fe, Co and Ni.

 The acid solution having the above composition is adjusted to pH 1.5-4.5 by means of a solution of anrm or caustic soda and is heated to a temperature of 40-800C. The titanium or titanium alloy object, cleaned, which is defatted and pickled by conventional methods, is immersed in said acid solution for 3 to 15 minutes, whereby it is formed on said titanium surface or one of its alloy a lubricant coating consisting of metal fluoride, suitable for cold forming.

 The metal fluoride layer mentioned above can be used in practice as a lubricating coating on titanium or alloy surfaces, but because of its insufficient adhesion to the metal support, problems have arisen as a result of chipping of the coating layer, which causes a seizure phenomenon when the object is subjected to cold forming.

The author of the present invention has attempted to solve the problem by adding additives to the aqueous solution of depositing a conversion layer on titanium or one of its alloys, a pH 1.5 solution. 4,5, containing fluoride ions and one or more metal ions selected from
Mg, Ca, Mn, Fe, Co, Ni, Zn and Mo. These attempts have resulted in the above-mentioned problem being solved by the addition to the above-mentioned coating solution of one or more additives selected from organic chelating agent, a high molecular weight organic compound, soluble in water, and a surfactant.

 The organic chelating agent used for the abovementioned aqueous solution for depositing a conversion layer may be chosen from gluconic acid, citric acid, tartaric acid, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), succinic acid, tannic acid, malic acid, etc. Of these, gluconic acid, citric acid, tartaric acid and ENTA are particularly effective, and the added amount of any of these acids is 0.1-2 g / liter. If this amount is less than 0.1 g / liter, the effect of the addition is not fully manifested. By cons, if we add an amount greater than 2 g / liter, no additional effect is observed.

 The water-soluble, high molecular weight organic compound may be selected from polyvinyl alcohol, gelatin, polyvinylpyrrolidone, etc., and the added amount of any of these compounds is 0.1- 10 g / l.

If this amount is less than 0.1 g / liter, the effect of the addition is not fully manifested. If this amount exceeds 10 g / liter, the deformability of the metal fluoride coating decreases.

 The surfactant may be of an anionic, cationic, ampholytic or nonionic type. Of these, the nonionic type is the most advantageous. Examples of surfactants which can be used in the present invention are: polyoxyethylene fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl ether phosphate, alkyl sulfate, sodium sulfate, alkylaryl, alkylaryl phosphate, fatty amide, alkylpropylenediamine, polyethylene glycol fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, fatty acid diethanolamide, polyoxyethylene alkylaryl ether, ethoxylated tall oil, acid ester and polyol, alkyldimethylamine oxide, etc.Normally, the aryl group contained in these compounds is phenyl or naphthyl. The alkyl group contains about 2 to 20 carbon atoms. In the case where the compound is alkoxylated, it may contain about 2 to 15 moles of alkylene oxide (eg, ethylene oxide or propylene oxide).

 The added amount of the surfactant is from 0.01 to 3 g / liter. If this amount is less than 0.01 g / liter, the effect of the addition is not fully manifest, whereas if it exceeds 3 g / liter, a large amount of the surfactant goes into the bath rinsing the next step, which is disadvantageous with respect to the pollution of the environment and, in addition, no additional effect is obtained.

 The present invention is illustrated by means of the descriptive and nonlimiting examples hereinafter.

Examples
A titanium wire 3.0 mm in diameter and 200 mm in length was subjected to an immersion process comprising the successive stripping steps (HNO3 - HF), hot water rinsing, formation of a layer of conversion (68-720C, 10 minutes), rinsing with water, rinsing with hot water, then drying. Using an Amsler tester, the coated wire was stretched to breaking.

 Adhesion of the coating layer was evaluated by examining the remaining coating film on the tensile test wire at the point of failure.

 Table 1 shows, for the Examples and Comparative Examples, the composition of the aqueous coating solution for formation of a conversion layer, and the results of the adhesion test.

Table 1

<SEP> composition of <SEP><SEP> solution <SEP> Examples <SEP> Examples
<tb> aqueous <SEP> of <SEP> depot <SEP> of a <SEP> comparative <SEP> layer
<tb> of <SEP> conversion <SEP> (ph <SEP> 2.6) <SEP> 1 <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 1 <SEP> 2 <SEP > 3
<tb> NaF # HF <SEP> g / l <SEP> 30 <SEP> 30 <SEP> 35 <SEP> 25 <SEP> 35 <SEP> 35 <SEP> 30 <SEP> 25
<tb> Zn2 + <SEP> g / l <SEP> 3 <SEP> 3 <SEP> 3 <SEP> 3
<tb><SEP> (nitrate <SEP> of <SEP> zinc)
<tb> Mn2 + <SEP> g / l <SEP> 4 <SEP> 3 <SEP> 3 <SEP> 3
<tb> (sulfate <SEP> of <SEP> manganese)
<tb> PO @ 3- <SEP><SEP> g / l <SEP> 3 <SEP> 2 <SEP> 2
<tb> (Phosphoric acid <SEP>)
<tb><SEP> EDTA <SEP> g / l <SEP> 0.7
<tb> acid <SEP> citric acid <SEP> g / l <SEP> 0.5 <SEP> 0.3
<tb> Polyvinyl <SEP> g / l <SEP> 0.5 <SEP> 0.5 <SEP> 0.8
<tb> agent <SEP> surfactant <SEP> i <SEP>
<tb> (polyoxyethylene <SEP> * <SEP> g / l <SEP> i <SEP> 0.05 <SEP> 0.2 <SEP> 0.05
<tb> nonyl-phenol-ether)
<tb> weight <SEP> of <SEP> layer <SEP> (g / m2)
<tb> trioxide <SEP> from <SEP> chrome <SEP> to <SEP> 5%,
<tb> 4.0 <SEP> 5.3 <SEP> 5.6 <SEP> 5.4 <SEP> 4.3 <SEP> 4.5 <SEP> 4.9 <SEP> 5.5
<tb> 75 C, <SEP> 15 <SEP> minutes)
<tb> adhesion <SEP> of <SEP><SEP> Film <SEP> of <SEP> G <SEP> G <SEP> G <SEP> G <SEP> G <SEP> NG <SEP> NG <SEP > NG
<tb> coating
<Tb>
Method for evaluating the strength of * 7 moles of polyoxyethylene film G = the coating film remains whole.

NG = peeling of the coating film is observed
As shown in Table 1, the addition of one or more compounds selected from an organic chelating agent, a water-soluble, high molecular weight organic compound, and a surfactant to an aqueous depot solution. a conversion layer, containing fluoride ions and metal ions, makes it possible to form a coating layer on the surface of titanium or one of its alloys, which gives very satisfactory results.

The coating layer made by the present invention is resistant to chipping during cold forming and does not cause galling.

Claims (1)

 CLAIM  Aqueous coating solution for the deposition of a chemical conversion layer on titanium or one of its alloys, at pH 1.5-4.5, containing fluoride ions and one or more metal ions selected from Mg, Ca, Mn , Fe, Co, Ni, Zn and Mo, characterized in that said aqueous chemical treatment solution is selectively added with one or more compounds chosen from an organic chelating agent (quantity added: 0.1-2 g / liter), an organic compound high molecular weight, soluble in water (amount added: 0.1-10 g / liter) and a surfactant (amount added: 0.01-3 g / liter).