CN104073854A - Rare earth/molybdate passivation treatment fluid for tin coating - Google Patents

Abstract

The invention relates to a rare earth/molybdate passivation treatment fluid for a tin coating. The rare earth/molybdate passivation treatment fluid for the tin coating is characterized in that 20-30g/L of molybdate and 3-5g/L of rare earth salt are mixed in a mass ratio of (4-10):1 to prepare a basic solution, adding an additive into the basic solution, stirring by adopting a magnetic stirrer, so that a passivation solution is obtained, and regulating pH value of the obtained passivation solution to be 4.0-6.0 with sulphuric acid, so that the rare earth/molybdate passivation treatment fluid is obtained, wherein molybdate is one of ammonium molybdate and sodium molybdate, and rare earth salt is one or two of nitrate or chloride of lanthanum or cerium; the additive is one or more than one of 2-5g/L of citric acid, 5-10g/L of tartaric acid and 0.5-2g/L of malic acid. The rare earth/molybdate passivation treatment fluid for the tin coating is short in treatment time, corrosion resistance of a passivating film is excellent, and the rare earth/molybdate passivation treatment fluid for the tin coating is economic and environment-friendly.

Description

A kind of rare earth/molybdate passivation treatment liquid of tin plating layer

technical field

The invention belongs to the technical field of surface treatment, and relates to a preparation method of a rare earth/molybdate passivation film on a tin plating layer.

Background technique

As one of the key varieties developed by my country's metallurgical industry, tinplate is widely used in food and canning and printing iron industries. With the improvement of people's living standards, the demand for tinplate is also increasing. In the production process of tinplate, after the strip steel is tinned and reflowed, in order to improve the corrosion resistance of the tinplate layer and prevent the tin layer from oxidizing and yellowing during storage or baking, the tinplate must be treated. passivation treatment. At present, chromate is mainly used for passivation of tin plate. Since hexavalent chromium in chromate is extremely harmful to humans and the environment, it is imperative to replace hexavalent chromium passivation treatment.

At present, chromium-free passivation technologies mainly include inorganic and organic. Among them, inorganic passivation mainly includes: tungstate passivation, molybdate passivation, phosphate passivation, titanium salt passivation, zirconate passivation and rare earth passivation, etc. Both layers have a certain protective effect, but the effect is not as good as the passivation effect of chromate. Organic passivation mainly includes: oleic acid passivation, phytic acid passivation, amine and protein passivation, and azole passivation, among which the corrosion resistance of the tin plating layer after oleic acid passivation is greatly improved, but It is necessary to use acetone to remove excess oleic acid; amine and protein passivation are used to treat the tin plate by electrolysis, and the passivation film of the tin plate has certain oxidation resistance and sulfur resistance. The anti-oxidation ability and welding performance of the tin plating layer after azole passivation are improved.

The electrochemical passivation method of rare earth/molybdate on tin plating has many advantages: (1) The passivation method is simple and the passivation time is short. (2) Passivation film formation is completed on the working electrode in one step, and the film thickness is controlled by polymerization time, polymerization potential, and current density. (3) No chromium-containing substances are used in the reaction process, which is an environmentally friendly process. (4) An electrochemical passivation film of the tin-plated layer with excellent corrosion resistance can be obtained.

Contents of the invention

The object of the present invention is to provide a rare earth/molybdate cathodic passivation treatment solution for tin plating, which has short treatment time, excellent corrosion resistance of passivation film, and is economical and environment-friendly.

The technical solution adopted is:

A rare earth/molybdate electrochemical passivation treatment solution for tin plating, the base solution is prepared by mixing 20g/L~30g/L molybdate and 3~5g/L rare earth salt according to the mass ratio of 4~10:1 , add additives to the base liquid, stir with a magnetic stirrer to obtain an electrolyte, adjust the pH value of the obtained electrolyte to 4.0-6.0 with sulfuric acid, and obtain;

The above-mentioned molybdate is one of ammonium molybdate or sodium molybdate, and the rare earth salt is one or both of the nitrate or chloride of lanthanum or cerium; the additives are citric acid 2~5g/L, tartaric acid 5~ One or more of 10g/L or malic acid 0.5~2g/L.

The present invention does not contain highly toxic hexavalent chromium, and performs electrochemical passivation on the tin plating layer at a working temperature of 30-50°C. The reaction is completed in one step, and the reaction process is controllable. It is an environmentally friendly process. The tin plating obtained after the treatment of the present invention Layer passivation film uniform, fine, excellent corrosion resistance.

Detailed ways

Example 1

A kind of rare earth/molybdate electrochemical passivation treatment liquid for tin-plated layer, which is prepared by mixing 20g/L sodium molybdate and 5g/L cerium nitrate according to the mass ratio of 4:1 to prepare the base liquid, and add it to the base liquid Add 2 g/L of citric acid and stir with a magnetic stirrer to obtain a passivation solution (electrolyte), and adjust the pH value of the obtained passivation solution to 4.0~6.0 with sulfuric acid to obtain the product.

Example 2

A kind of rare earth/molybdate electrochemical passivation treatment solution for tin-plated layer, which is prepared by mixing 30g/L ammonium molybdate and 3g/L lanthanum nitrate according to the mass ratio of 10:1 to prepare the base solution, and add it to the base solution Add 4 g/L of citric acid, 10 g/L of tartaric acid, and 0.5 g/L of malic acid, and stir with a magnetic stirrer to obtain a passivation solution. The pH value of the obtained passivation solution is adjusted to 4.0~6.0 with sulfuric acid.

Example 3

A kind of rare earth/molybdate electrochemical passivation treatment solution of a tin-plated layer is prepared by mixing 24g/L sodium molybdate and 4g/L cerium nitrate according to a mass ratio of 6:1 to prepare a base solution, and put it into the base solution Add 5 g/L of citric acid and 5 g/L of tartaric acid, stir with a magnetic stirrer to obtain a passivation solution, adjust the pH value of the obtained passivation solution to 4.0~6.0 with sulfuric acid, and obtain the product.

Claims (4)

1. a kind of rare earth/molybdate electrochemical passivation treatment liquid of tin-plated layer, it is characterized in that according to mass ratio 4～10:1 with 20g/L～30g/L molybdate and 3～5g/L rare earth salt Mix and prepare the base liquid, add additives to the base liquid, stir with a magnetic stirrer to obtain a passivation solution, and adjust the pH value of the passivation solution to 4.0~6.0 with sulfuric acid to obtain the product; The above-mentioned molybdate is one of ammonium molybdate or sodium molybdate, and the rare earth salt is one or both of the nitrate or chloride of lanthanum or cerium; the additives are citric acid 2~5g/L, tartaric acid 5~ One or more of 10g/L or malic acid 0.5~2g/L. 2. the rare earth/molybdate electrochemical passivation treatment solution of a kind of tin-plated layer according to claim 1 is characterized in that: be by the cerium nitrate or the cerium chloride of 20g/L sodium molybdate and 5g/L Cerium was mixed according to the mass ratio of 4:1 to prepare the base liquid. Add citric acid 2g/L to the base liquid and stir with a magnetic stirrer to obtain a passivation solution. The pH value of the passivation solution was adjusted to 4.0~6.0 with sulfuric acid , get it. 3. the rare earth/molybdate electrochemical passivation treatment solution of a kind of tin-plated layer according to claim 1, is characterized in that: be by the lanthanum nitrate or chloride of the ammonium molybdate of 30g/L and 3g/L Lanthanum is prepared by mixing the base liquid according to a mass ratio of 10:1, adding 4 g/L of citric acid, 10 g/L of tartaric acid, and 0.5 g/L of malic acid to the base liquid, stirring with a magnetic stirrer to obtain a passivation liquid, and obtaining The pH value of the passivation solution is adjusted to 4.0~6.0 with sulfuric acid. 4. the rare earth/molybdate electrochemical passivation treatment liquid of a kind of tin-plated layer according to claim 1 is characterized in that: by the cerium nitrate of the sodium molybdate of 24g/L and 4g/L according to mass ratio 6:1 mixed to prepare the base liquid, add 5 g/L of citric acid and 5 g/L of tartaric acid to the base liquid, stir with a magnetic stirrer to obtain a passivation liquid, and adjust the pH value of the passivation liquid to 4.0~ with sulfuric acid 6.0, that is.