Electroplating on aluminum and aluminum alloys is much more difficult and complicated than electroplating on metal materials such as steel and copper. The main reasons are as follows.
1, Aluminium and aluminium alloy with high affinity for oxygen, easy to generate oxide film, and once this layer of oxide film is removed and will be in a very short time to produce a new layer of oxide film, the serious influence the adhesion strength of the coating.
2. The electrode potential of aluminum is very negative, and it is easy to replace the metal ions with positive potential when immersed in electroplating solution, which affects the bonding strength of the coating.
3. The expansion coefficient of aluminum and aluminum alloy is larger than that of other metals, so it is not suitable to conduct electroplating in the range of large temperature change. The expansion coefficient of aluminum and aluminum alloy and other metal coatings will cause greater stress, which will make the adhesion between the coating and aluminum and aluminum alloy not strong.
4. Aluminum is a bisexual metal, soluble in acid and alkali, and unstable in acid and alkaline electroplating.
5. Aluminum alloy die-casting parts have sand holes and pores, which can remain liquid and hydrogen, which are easy to bubble, and also reduce the bonding force between the coating and the matrix metal.
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