100 Questions on Basic Electroplating Knowledge (Part 4)
16. What should be added to the nickel plating solution to promote anode dissolution? Can a large amount of boric acid be added?
Answer: To promote the dissolution of the nickel anode, an appropriate amount of chloride ions should be added. Boric acid does not have the effect of promoting the dissolution of the nickel anode.
17. What harmful impurities should be noted in the bright nickel plating solution?
Answer: In bright nickel plating, attention should be paid to: (1) Impurities in industrial raw materials. For example, nickel sulfate contains copper, zinc and nitrate, and the anode nickel plate contains iron and other impurities; (2) Pollution during the production process. Such as incomplete cleaning, copper and chromium brought in from products or hangers, decomposition products of organic additives. These are all harmful impurities in bright nickel plating and should be excluded.
18. Is the peeling and flaking of the chromium coating after nickel plating mainly caused by poor pre-treatment before plating?
Answer: The peeling of the coating after nickel plating and chromium plating is not only due to poor pre-treatment before plating, but also related to the condition of the plating solution and the phenomenon of double-layer nickel.
19. Why can’t metallic chromium be used as the anode for chromium plating?
Answer: Metallic chromium is not used as the anode for chromium plating mainly because it dissolves very easily during the plating process. The current efficiency of the anode metallic chromium dissolving is much higher than that of the cathode metallic chromium depositing. As a result, as the plating process proceeds, the chromium content in the plating solution will increase continuously, making normal plating impossible. Moreover, metallic chromium is very brittle and difficult to process into various shapes, so it cannot be used as a full metallic chromium anode. Generally, lead or lead alloys are used as the anode in the chromium plating process.
20. Why does a part of the chromium coating turn brown?
Answer: The appearance of a part of the brown film in the chromium coating is mainly caused by insufficient sulfate ions. In addition, if the plating solution temperature is too low or is disturbed by impurities (such as Cl-), a brown film may also appear in the chromium coating.
