Method for plating hard chromium on surface of metallic material

Abstract

The present invention discloses a method of plating hard chromium on the surface of metal. The characteristic is that it concludes the following process: (1) Cleans and activates the surface of metallic material in common way; (2) plates hard chromium: plating hard chromium after the surface of the metal is cleaned and activated. The temperature of plating solution is 58 - 65 deg. C; Current density is 30 - 80 A / dm2; the proportion of cathode and anode area is 2 - 3:1; the component of plating solution (in one liter) is: Chromic anhydride is 220-280g; Sulfuric acid: 2.5 - 4.5 g; Cr (III): 1.5 - 7 g; the additive of organic compound LD-5660: 14 - 20 ml. This invention can increase current efficiency and speed of sedimentation. The coat is anti-corrosive.

Description

technical field [0001] The invention belongs to the field of metal material surface treatment, in particular to an electroplating process for anti-corrosion hard chrome plating on the surface of metal materials. Background technique [0002] In industrial production, electroplating is required on the surface of metal products to make the surface of metal products have special functions and / or decorations, such as certain hardness, corrosion resistance, luster, and beautiful appearance. At present, electroplating hard chromium on the surface of metal materials to obtain a hard chromium protective coating has a wide range of applications, because the surface friction coefficient of the hard chromium coating is low, and there is a self-healing oxidant Cr 2 o 3 Surface film, so excellent wear resistance. [0003] Usually, the hard chromium electroplating method is an electroplating chromium plating process using rare earth additives or fluorine-containing additives. Although ...

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Problems solved by technology

Although this method has the advantages of certain hardness, good corrosion resistance, luster, beautiful appearance and excellent wear resistance, it has the following disadvantages due to the slow transmission of the electrolyte in the plating solution: 1. Due to the use of rare earth or Fluorine-based catalysts, the electrolyte in the plating bath is transported slowly, so the current efficiency is low; 2. Due to the slow transport of the electrolyte in the bath, the deposition rate of the coating is slow; 3. Due to the slow transport of the electrolyte in the bath, the electroplating bath has poor deep plating and throwing ability , when electroplating workpieces with complex shapes, pictographic anodes must be used to ensure that each part of the workpiece can be electroplated with a coating; and due to the poor uniformity of the coating, the workpiece must be ground after plating to make the surface of the workpiece evenly coated; 4. The coating is corrosion-resistant Poor performance, its salt spray test (hereinafter expressed by NSS) is only about 8 grades in 24 hours; 5. The coating crystal is coarse and dull, so grinding is often carried out after plating to improve the brightness of the workpiece and reduce friction; 6. Rare earth additives or fluorine-containing additives cause the plating solution to corrode the substrate, plating tank and anode of the plated workpiece greatly.