Electroplating techniques for brazing assemblies.

A chisel joint is a joint made by means of a chisel weld process and is a non-detachable joint. For soft brawling, lead and tin solders are used, and for hard brawling copper and zinc and silver and bronze solders. After welding, a circular solder layer remains on the surface of the combined parts. During electroplating, corrosion will become black, flow will cause the plating to bubble, etc. Special measures need to be taken. (1) Cleaning of tongs Before electroplating of tong-welded composite parts, the tongs (welding agents) should be cleaned first. Since the surface is activated during welding, various tongs have been used as activated substances. Soft tongs include fragrance, and hard tongs contain fluoride. Soft Tongs can be cleaned by a mixture of alcohol and gasoline.Hard chisel will form a glassy substance on the solder layer, which is very hard to touch, affecting pre-treatment and electroplating. It can be boiled in hot water from 80 to 10 ° C for 1 hour. After the chisel is soft, clean it with a brush. 2.Oil removal and corrosion 1) In the pre-plating treatment of the chisel joint, in order to prevent the solder layer from becoming black, the soft chisel Joint should be chemically oiled in a weak alkaline solution that does not contain NaOH and activated for a short time in diluted sulfuric acid, which can maintain the original luster of the solder surface. It is avoided to corrosion with strong acid. In order to ensure the bonding force of the plating, to activate the surface of the solder without damage to the part matrix, a mixture solution of ammonia and hydrofluoric acid should be used. Ammonia does not affect the activation of hydrofluoritic acid on the solder. However, it can inhibit the corrosion of the acid on the component body. Hydrofluoric acid salts may also be used, as follows: Hydrofluoritic acid 10-25% Dioxygenate 2-5% Room temperature 1-3 minutes 2) For silver welding parts, if sound corrosion with ordinary tricarbonate solution is used, it is easy to produce brown ashes on the welding layer. The improved formulation is: Nitric acid 15%, Phosphic acid 60%, acetic acid 25%,30 ° C, L 1 min. This solution can prevent the discoloration of the solder layer and prevent the excessive corrosion of the part base. For copper composite parts joined by silver soldering, if only acid washing is passivated, a line of deionized water washing should be added after passivation to prevent the production of black ash. 16! When a combination of aluminum parts is chemically treated and anodized, it is easy to see the color of the metal and the solder layer not being the same. Magnesium alloys should be chosen as solder materials rather than silicon alloys, because the silicon element enters the anodizing film and will turn the solder layers into a dark grey color. Electroplating of non-seamless welding assemblies When the electrochemical activity and machining state of the parts in the welding assembly differ greatly, Pre-treatment should be applied with solvent degrease and temperature spray sand to achieve a uniform cleanliness on the surface of the parts. After weak corrosion, copper or zinc coating, the electrochemical activity on the surface is uniform, and other metals can be electroplated.