1 Introduction

A variety of Nickle Electroplating and electroplating decorative chrome as a conventional plating, in the production occupies a large proportion. Because of its complex process, involving more processes, so there is a high probability of failure, especially the more sophisticated or expensive workpieces. If the chemical properties of Nickle Electroplating are particularly stable, if the original rework method (such as mixed nitric acid method, anti-salt S method and electrolysis method) for plating, the workpiece matrix will produce corrosion or reduce the accuracy of the workpiece, resulting in a huge (even Difficult to make up) the loss. The author through practice, to find out the solution to the problem of electrification Nickle Electroplating failure problem, instead of the traditional method, in the production received good results. The method utilizes a chemical reaction to remove the nickel-plated layer, which avoids the electrochemical removal of the nickel-plated layer during the process of low current density, which is difficult to remove the clean ills and overcomes the traditional chemical method of withdrawing nickel too slowly or Serious shortcomings of corrosion.

2 back Nickle Electroplating process

2.1 Experimental materials

(For copper matrix), concentrated sulfuric acid (ρ = 1.84g / mL), nickel powder B (applied to steel matrix), potassium cyanide (or sodium cyanide).

Nickle Electroplating powder A, B are Hong Kong Zhongxingda International Trade Co., Ltd. produced.

2.2 Experimental samples

Sample I is the coating Cu / EP · Ni15bCr0.3r, and the sample Ⅱ is the coating Fe / EP · Cu10Ni15bCr0.3r.

2 samples each have 20, specifications are ∠ 5 × 5mm angle, thickness 2mm, length 200mm.

2.3 process flow

Degreasing - Cleaning - Refining Chromium - Cleaning - Nickel - Cleaning - Stripping - Cleaning - Drying.

This process can be repeated if the plating is thick and the reject is not complete at all.

Before the nickel is removed, the oil on the surface of the workpiece must be cleaned and the chrome plating layer should be completely withdrawn. Otherwise, the chrome layer will prevent the chemical reaction from proceeding. The nickel-back process can also be used to remove copper cyanide plating on copper or iron substrates. In particular, it is not possible to use the nickel powder used to withdraw the nickel layer on the copper substrate for the removal of the nickel layer on the steel substrate, otherwise severe pitting will occur. With the increase of the amount of nickel and the reaction of chemical reaction, the reaction product is increasing and the viscosity of the solution increases, and the nickel recovery rate decreases gradually. When the reaction is brought to a certain extent, even if the nickel powder and sulfuric acid are added in the original solution, The nickel speed will not be accelerated, then the new solution should be replaced.

The main process of the solution formula and operating conditions are as follows:

2.3.1 Crushed

Using φ = 50% hydrochloric acid solution, soaked at room temperature until the chrome plating layer to clean up so far.

2.3.2 Nickle Electroplating reduction

Back nickel powder A or B80 ~ 100g / L

Concentrated sulfuric acid 10 ~ 20g / L

θ60 ~ 80 ° C

Soaked until the surface was dark black so far. Stirring can speed up the nickel withdrawal. It should be noted that sulfuric acid should be added to the solution before heating and stirred evenly to prevent splashing.

2.3.3 stripping

Using ρ = 100 ~ 200g / L sodium cyanide solution, at room temperature soaked in dark black film to clean up so far.

2.4 rework

The Nickle Electroplating layers on all the test samples were clean (90 ° corners and no residue), the surface without corrosion, smooth as plating before. Will clean the workpiece to clean and dry, slightly polished in accordance with the process requirements to re-plating.