100 Questions on Basic Electroplating Knowledge (Part 2)
6. Why is it necessary to rinse the workpiece with clean water between chemical degreasing and weak acid etching?
Answer: Because the usual chemical degreasing solution is alkaline. If the degreasing solution is directly brought into the acid etching solution, an acid-base neutralization reaction will occur, reducing the concentration and effectiveness of the acid. The products of the neutralization reaction adhere to the workpiece, affecting the quality of the coating. Therefore, after chemical degreasing, the workpiece must be thoroughly rinsed with clean water before entering the acid etching solution.
7. What are the common causes of burrs and coarse grains on the electroplated layer, and how can they be solved?
Answer: The appearance of burrs and coarse grains on the electroplated layer is mainly caused by the contamination of the plating solution with suspended impurities. The sources of these impurities include dust in the air, sludge from the anode, and hydrolysis products of metal impurities. In addition, there may be abnormal composition of the plating solution and unsatisfactory operating conditions. The solutions are: adjusting the composition of the plating solution and operating conditions. If the problem is caused by suspended impurities, the plating solution should be filtered.
8. What is the basic procedure for preparing an electroplating solution?
Answer: The basic procedure for preparing an electroplating solution is as follows: (1) First, place the measured electroplating chemicals into a small tank (preparation tank), then add an appropriate amount of water to dissolve them. Do not directly pour the chemicals into the plating tank. (2) Use various chemical methods to remove impurities from the solution and treat it with activated carbon. (3) After the solution has been treated and allowed to settle, filter it into a clean plating tank and add water to the standard volume. (4) Adjust the process parameters of the plating solution (pH value, temperature, additives, etc.). (5) Finally, perform low current density electrolytic deposition to remove other metal ion impurities until the solution is suitable for operation.
9. Why should the rack be coated with insulating material?
Answer: When manufacturing the rack, except for the contact and conductive parts of the hook and the product, the rest should be coated with insulating material to reduce current loss and metal loss, ensure that only the effective area of the product is electroplated, increase the effective current, and make the rack more durable.
10. How effective are sulfuric acid and hydrochloric acid in rust removal? Can nitric acid be used for rust removal?
Answer: Generally, concentrated hydrochloric acid is the most effective for rust removal on products, achieving high efficiency and not causing over-corrosion or damage to the base metal even if the time is slightly longer. Sulfuric acid is good at removing surface rust stains but is slow in rust removal, and if the time is too long, it can cause over-corrosion and significant damage to the base metal. Nitric acid cannot be used for rust removal because it has strong oxidizing properties and will oxidize metals upon contact, generating large amounts of toxic nitrogen oxides gas.
