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AssigneeNippon Paint Co., Ltd.
InventorsTamotsu Sobata, Akio Tokuyama, Shoji Shiraishi, Seiichiro Shirahata
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To treat an iron-based, zinc-based, and an aluminumbased surfaces etc. with zinc phosphate using the same solution, a treating solution is adjusted in concentrations so as to contain a simple fluoride in a range of 200.about.500 mg/l upon converting into a HF concentration and to contain a fluoride complex in a range shown in the following formula; ##EQU1## and also, it is adjusted in an active fluorine concentration so as to be 15.about.130 .mu.A at a value indicated by a silicon electrode meter. Instead of such adjusting, aluminum ions in the treating solution is precipitated in an outside of a treating bath to separate them from the treating solution and then, this treating solution may be returned in to the treating bath.
A method for forming a zinc phosphate coating on a metal surface containing aluminum, comprising placing the metal surface in a treating bath in contact with a treating solution, passing the treating solution to an external bath, adding a simple fluoride to the treating solution in the external bath thereby precipitating aluminum ions in the external bath, separating the precipitated aluminum from the treating solution, and returning the treating solution from which the precipitated aluminum has been separated to the treating bath, wherein a simple fluoride is not added to the treating solution in the treating bath, wherein the treating solution in adjusted in concentration so as to contain the simple fluoride in a concentration range of 200.about.300 mg/l upon converting into a HF concentration and the fluoride complex in a range ##EQU6## and also, is adjusted in the active fluorine concentration at a value of 15.about.40 A as indicated by a silicon electrode meters and wherein the silicon electrode meter is set up so that, under a condition where a solution being measured has the same characteristics as the treating solution and is not shone with a light, a p-type silicon electrode having a 0.5 square inch area in contact with a solution and a platinum-made inactive electrode are brought in contact with the solution being measured, a direct electric current source is connected between these electrodes and the value of electric current is read, wherein the solution being measured is still stood or arranged to make a constant current and then, under these conditions, a direct electric current voltage of 1.2 volt is charged between both the electrodes and the active fluorine concentration is known by reading the value of electric current when it becomes to a stationary value.
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
Characterised by the process: controlling or regulating of the coating process
Containing also phosphates: containing also zinc cations
Coating metallic material
Term ended 21 Mar 2012 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
The present invention relates to a method for treating (phosphating) a metal surface with zinc phosphate being provided for coating etc. and, in detail, to a phosphating method for forming a zinc phosphate coating film on an iron-based, zinc-based, and an aluminum-based surfaces as well as a metal surface having these two or more surfaces in combination and simultaneously, wherein the coating film is desired to be suitable for electrocoating, in particular, for electrocoating of a cation type and to be superior in the adhesion character, corrosion-resistance, in particular, in warm brine-resistance and resistance for rust of a scab type (hereinafter, referred to as scab-resistance).
Metal materials have been used in various fields such as automobile bodies and other automobile parts, building materials, furniture and so on. The metals are treated with zinc phosphate (phosphating) as a coating pre-treatment in order to prevent corrosion due to oxygen, sulfur oxides in the air, rain water, and sea water etc. The zinc phosphate coating film thus-formed requires adhesion-superiority with a metal surface that is a substrate and with a coating film thereon formed (secondary adhesion) as well as to have sufficient rust-resistance even under corrosive surroundings. In particular, since the automobile body repeatedly suffers contact of brine and variation of weather conditions (dry or wet) at a wounded place of the outside plate, it is desired to have scab-resistance and a higher degree of warm brine-resistance.
Recently, there are increasing the cases of treating metal materials composed of two or more kinds of metal surfaces with zinc phosphate. For example, in order to further elevate corrosion-resistance of the automobile body after the coating, a zinc- or zinc alloy-plated material is used in only one side of steel materials. Like this, when the hitherto known phosphating treatment with zinc phosphate is carried out for a metal surface having both an iron-based and zinc-based surfaces, there is caused a problem that the corrosion-resistance and secondary adhesion on the zinc-based surface is inferior compared with those on the iron-based surface. Because of this, there has been proposed, for example, in Japanese Official Patent Provisional Publication, showa 57-152472 etc., a method of forming a zinc phosphate coating film which is suitable for electrocoating on a metal surface having both an iron-based and zinc-based surfaces simultaneously. In this method, manganese ions in a concentration of 0.6.about.3 g/l and/or nickel ions a concentration of 0.1.about.4 g/l are contained in a treating bath wherein the concentrations of zinc ions, phosphate ions, and a coating film-converting accelerator are controlled. Also, there has been proposed in Japanese Official Patent Gazette, showa 61-36588, an art wherein fluorine ions are added in a concentration of 0.05 g/l or more, together with manganese ions in order to lower treating temperature.
FIG. 1 is an outline diagram showing one example of an equipment which is used in carrying out the method for treating (phosphating) a metal surface with zinc phosphate relating to the present second invention.
FIG. 2 is an outline diagram showing an equipment which is used in an example for comparison 9.
Hereinafter, the present second invention is explained with referring to the outline diagrams of an equipment used in practice.
FIG. 1 is an outline diagram showing an example of the equipment which is used in carrying out the method for treating (phosphating) a metal surface with zinc phosphate relating to the present second invention. As seen in this diagram, into the treating bath 1 is placed the treating solution 2, in which a metal surface is dipped. In this treating bath 1, a sensor (which is not shown in the diagram) is set to survey the concentration of aluminum ions and the pump P.sub.1 is arranged to pump out continuously or intermittently the treating solution 2 in the treating bath 1, when the concentration of aluminum ions reaches a certain degree. The treating solution 2 pumped out is led to the bath for precipitating 3, to which a simple fluoride is added. Concentration of the simple fluoride at this time is set, for example, as described above. By doing this, the aluminum ions form sludge containing aluminum. The treating solution 2 containing the sludge containing aluminum is led to the bath for separating the precipitate 4 and the sludge containing aluminum is separated, for example, according to the forementioned manner and then, this treating solution 2 is returned to the treating bath 1. Besides, the bath for precipitating 3 and the bath for separating the precipitate 4 are separately settled, but the precipitate separation may be carried out in the bath for precipitating 3.
Hereinafter, the practical examples of the present invention and the examples for comparison are presented, but the present invention is not limited within the undermentioned examples.