Trivalent chromium electroplating method of cold-rolled sheet

Abstract

The invention discloses a trivalent chromium electroplating method of a cold-rolled sheet. Plating liquid is prepared from chromium sulfate with the density being 135-145 g / L, sodium sulfate with the density being 210-230 g / L, potassium sulfate with the density being 30-40 g / L, magnesium sulfate with the density being 20-30 g / L, boric acid with the density being 65-75 g / L, formic acid with the density being 0.1-0.3 mol / L, oxalic acid with the density being 0.2-0.4 mol / L, sodium citrate with the density being 0.3-0.5 mol / L, sodium dodecyl sulfate with the density being 0.001-0.002 mol / L, benzene sulfinic acid sodium salt with the density being 0.0015-0.0025 mol / L, gamma-methacryloxypropyltriethoxysilane with the density being 0.2-0.4 mol / L and dibutyltin diacetate with the density being 0.5-0.7 g / L. The electroplating technology includes the steps that a graphite anode is adopted, the work temperature is about 50-55 DEG C, the pH is 3.5-4.5, the current density is 22-24 A / dm<2>, the electroplating time is 60-90 min, and the rotating speed of a stirrer is 100-120 r / min.

Description

technical field [0001] The invention relates to the technical field of electroplating, in particular to a trivalent chromium electroplating method for cold-rolled sheets. Background technique [0002] Chromium plating is widely used in industry because of its bright, hard, anti-tarnish, good wear-resistant and corrosion-resistant properties. For a long time, the chromium plating process is a hexavalent chromium plating process using chromic acid as the chromium source. As an electroplating process, hexavalent chromium electroplating has some technical defects, such as extremely low cathode efficiency; poor dispersion and coverage of chromium plating; and no intermediate power interruption during the chromium plating process. What's more, hexavalent chromium is one of the most serious and difficult pollution sources in the electroplating industry. [0003] With the enhancement of people's awareness of environmental protection, hexavalent chromium, as a harmful pollution sou...

AI Technical Summary

Problems solved by technology

It has the following disadvantages: one is to use static plating solution for electroplating, and the pH near the cathode rises too fast, and it is impossible to obtain a coating with a thickness exceeding 5 μm; the other is that the plating solution uses aluminum sulfate as a conductive salt, which is easy to cause the plating solution due to its amphoteric characteristics. poor stability