Silver plating of aluminum and its alloys is much more difficult than silver plating of common copper parts, and the process is complicated. The main reason is that the properties of aluminum and its alloys are different from those of other metals. Aluminum is an amphoteric metal that reacts with both acid and alkali. If the pretreatment is slightly improper, it will cause surface over-corrosion. Moreover, aluminum and its alloys are highly susceptible to oxide film whether in air or in solution. If the oxide film is not removed, it will affect the bonding strength of the coating.

The most critical aspect of silver plating of aluminum and its alloys is the adhesion of the coating to the base metal. Therefore, a special treatment method must be adopted in order to obtain a silver plating layer having a good bonding strength on an aluminum substrate. The use of zinc immersion can better solve this difficulty.

Zinc immersion is based on the principle that the potential of aluminum is relatively negative, and replacement is easy in the electrolyte solution, and a thin layer of zinc is replaced. This layer of zinc is sandwiched between the base metal and the silver plating layer to enhance the bonding strength between the plating layer and the base metal.

In the process of silver plating of aluminum and its alloys, pay attention to the following points:

1) Whether it is degreasing or alkaline washing, the content of NaOH should not be too high, and the time should not be too long to avoid excessive corrosion on the surface.

2) The process of zinc immersion is the key to whether or not a satisfactory coating can be obtained. The zinc immersion is carried out twice because the zinc layer is rough after the first zinc immersion. After 1:1 HN0 is removed, the second zinc immersion is performed. After the second zinc immersion, only the zinc layer which is uniform, fine and has good adhesion to the substrate can be used to enter the next process.

3) Pay attention to the swing during the zinc immersion process to prevent the parts from overlapping each other and causing a local zinc-free layer.

4) If the quality of zinc immersion is found to be poor, use 1:1 HN0, and then re-soak the zinc.

5) After immersion in zinc, the parts should be charged with human tank when entering the cyanide copper plating solution, and then plated with high current for 2 minutes, then return to normal current. If the surface of the part is found to be black or dark during electroplating, the part can be taken out and treated before plating.

6) After the copper is plated with copper, it can be carried out in the normal process of silver plating of copper.

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Label: Silver plated on aluminum

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HASTELLOY®

Hastelloy Availability

Yuhong Group supplies Hastelloy C276, C22, X, B3 and B2. Most of these alloys are available in the form of plate, sheet, bar, pipe, tubing, pipe fittings, flanges and welding material. Request a Quote today on any of these alloys.

The registered trademark name, Hastelloy, is applied as the prefix name to more than twenty different highly corrosion resistant metal alloys produced by Haynes International, Inc. Thesesuperalloys, or high performance alloys, developed by Haynes International, are nickel-based steel alloys that exhibit traits that include high resistance to uniform attack, localized corrosion/oxidation resistance, stress corrosion cracking resistance and ease of welding and fabrication.

Alloys of identical chemical and mechanical properties are available from other manufacturers and offer excellent alternatives to the various Hastelloy® brand alloys.

The corrosion-resistant superalloys are widely used by the chemical processing, aerospace, and industrial gas turbine and marine industries. Additionally, due to the their reliable performance, areas of energy, health and environmental, oil and gas, pharmaceutical and flue gas desulfurization industries are increasingly using them.

What are the Characteristics of Hastelloy ?

High resistance to uniform attack
Outstanding localized corrosion resistance
Excellent stress corrosion cracking resistance
Good resistance to acids such as sulfuric, nitric, hydrochloric, hydrofluoric and chromic
Ease of welding and fabrication
High resistance to oxidation at elevated temperatures

In what Applications are Hastelloy alloys used ?

Chemical Processing Industry
Aerospace
Pharmaceutical
Oil and gas production
Components where exposure to high mechanical stress and sea water are required
Components exposed to flue gas or flue gas desulfurization plants

Superalloys, also known as high performance alloys, have become the steel of choice for corrosion resistance and versatility.

*Hastelloy® is a registered trademark of Haynes International, Inc.

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