Processing for forming Zn-Sn alloy layer through mechanical plating and Sn reduction disposition

Abstract

The invention provides a process for forming a Zn-Sn alloy layer through mechanical plating and Sn reduction disposition. The process comprises the steps of workpiece pretreatment before plating, establishment of a base layer on the surface of the workpiece, and alloyed plating thickening. A compound surfactant is used to change the characteristic of a plating solution, thus an environment in which continuous deposition of metal Zn powder on the surface of a plated part can be ensured, adsorption deposition plays a main role, and reduction carrying deposition plays an auxiliary role can be formed; a reduction deposition activator prepared by mixing a stannous salt, a ferrous salt, an ammonium salt, phosphoric acid and water is used for supplying Si element for the Zn-Sn plating layer through mechanical plating. The plating is smooth, bright, good in uniformity and high in compactness. As no metal Sn powder is adopted, carrying deposition of crude and large particles can be avoided, the reduced Sn atoms are preferentially adsorbed on the Zn powder and Zn powder alga-gobbets while the size of the Sn atoms is far less than that of the Zn powder and Zn powder alga-gobbets, under the same movement and impact conditions, the layer formation conditions of the plating are changed toward the direction favor of compaction and leveling, the utilization rate of non-ferrous metal is beneficial to being improved, and the production cost is lowered.

Description

technical field [0001] The invention relates to a process for mechanically plating a Zn-Sn alloy coating, in particular to a mechanical plating and tin reduction deposition method to form a zinc-tin alloy coating (Zn-Sn) on the surface of steel parts, which belongs to the mechanical coating process technology field. technical background [0002] Mechanical Plating is a surface treatment process that uses physical and chemical adsorption deposition and mechanical collision at room temperature and pressure to make metal powder form a coating on the surface of steel parts. A typical mechanical plating process is to put the parts that have been pre-plated into the mechanically driven plating cylinder, then add water and impact medium (glass pellets), and add metal powder and chemicals according to the predetermined coating thickness. During the process, a fluid environment with collision, rubbing and chemical agents is formed, so that the surface of steel parts is coated with z...

AI Technical Summary

Problems solved by technology

But think after the research of the inventor of the present application: the phenomenon that drives the co-deposition of metal powder with the reductive deposition of stannous salt, although exists, but relatively weak, and the process is comparatively slow, and deposition efficiency is low, will form the tin content greater than More than 5% of the mechanically plated Zn-Sn alloy coating cannot rely solely on the reduction of stannous salt, and metal tin powder must be added

For example, in mechanical plating of Zn-Sn25% alloy coating, the actual amount of tin powder added is generally 36-41% of the total amount of metal powder, and the effective utilization rate of metal tin powder is only about 60%.

In addition, the existing problems in the prior art are: 1) The citric acid-based activator has weak activation and is unstable in the solution, which makes the process cycle long, and the deposition rate of the coating above 30 microns decreases, and zinc powder and tin powder The utilization rate is low; 2) When the reduction deposition of tin ions in acidic aqueous solution is used as the main accelerator for the deposition of zinc powder and tin powder, after the Zn-Sn coating is formed, its coating composition and the alloy powder to be deposited The composition is very close, so that the reduction potential gradually decreases, resulting in slow deposition and low coating formation efficiency; 3) The particle size of commercially available tin powder is relatively coarse, which easily causes the internal structure of the coating to be loose, making the density lower than 60%, and the surface is rough. 4) The alloy element tin of the Zn-Sn alloy coating is added in powder form. During the co-deposition process, the coarse particles of tin powder have poor aggregation and are not easily absorbed or carried into the coating. The effective utilization rate of tin powder is low