Aluminium and aluminium alloy plating is more difficult, because aluminum has a strong affinity for oxygen, surface oxidation easily; Aluminum is metal, the sexes are not stable in acid and alkali; Aluminum potential is very negative, in the plating solution is easy by erosion and the replacement by metallized; The expansion coefficient of aluminium is most of the large metal, thus coating bubbles, fall off easily, affect the bonding force.
 
Aluminium and aluminium alloy plating is the key to special treatment before plating, remove natural oxide film, and prevent its form again, and aluminum in the electrolyte, prevent substitution reaction. As the navy overhaul aircraft factories, we often encountered in the process of repairing aluminium and aluminium alloy electroplating. By trial, error, the best process conditions. Aluminum alloy plating the parts surface glossiness is good not only, and binding force, corrosion resistance is also very good, meet the requirements of AIDS to navigation. In this paper, the aluminum alloy parts repair of old goods plating process.
1 process
Except oil (fat) off - used coating back - two - alkali corrosion - two cleaning cleaning - > to gray scale (a light) - two cleaning - a heavy zinc - two cleaning - back in addition to the zinc layer - two cleaning - the second heavy zinc and sulfuric acid neutralization, activation - cleaning - the chemical plating nickel - two cleaning - the activation - plating picks - two cleaning and passivation to two washing to dry, aging, test library.
2 main process
2.1 degreaser composition and process conditions
Sodium hydroxide, 40, 609 / L, 70 - a - 90 "c, 1 a Zmin.
Oil pollution serious first using organic solvent to clean.
2.2 the used coating
Refund the old plating is one of the key process aluminum tin plating.
2.2.1 used f layer solution composition and operating conditions
Nitrate money 1 0 a 150 L, room temperature, out so far.
2.2.2 used zinc layer solution composition and operating conditions
Sulfuric acid 10 a 150 L, room temperature, out so far.
2.2.3 refund used oxidation film solution composition and operating conditions of oxyhydrogen sodium 40 a 609 / L, 50, 90 "C, back so far.
2.24 in addition to back a Ni P alloy solution composition and technological conditions
7 00 ml/L nitric acid, sodium chloride 30 a 409 / L, six methyl tetramine 6 a 109 / L, 15 a ZoglL urea, room temperature.
(1) check out before plating parts should be dry or use the cold wind blow dry, prevent moisture and reduce the concentration of nitric acid, resulted in the corrosion of substrate.
(2) check out good plating parts should be cleaned quickly, in order to avoid the refund after plating surface a layer of black oxide film.
Aluminum alloy electroless nickel layer usually used remission nitric acid. Although the nitric acid oxidation is very strong, but the nitric acid of Ni P alloy coatings corrosion rate slower, except when a lot of No 2 back gas, pollution to the environment is very large. Precision parts out of a electroless Ni P alloy coatings after plating, nitric acid corrosion amount of the matrix metal often overweight, especially for bolt parts corrosion is especially obvious. Remission in order to overcome the chemical plating nickel layer of bolt corrosion defect parts, we after hundreds of times experiments, finally chose the nickel process. Remission in Ni P alloy coatings, corrosion of substrate is very small, not easy corrosion, back when plating the gas also is less, can guarantee the quality of plating back, improved working conditions.