Acid Copper

Acid copper plating is a widely used method for depositing a layer of copper onto metal objects. This process allows for thick layer of copper to be applied. This copper layer can be buffed to a beautiful satin or mirror finish.

Acid Copper does not react with non-oxidizing acids like dilute sulfuric acid, hydrochloric acid, or hydrobromic acid. Its reduction potential is higher than that of hydrogen, which means copper remains unreactive with these acids.

However, it can react with oxidizing acids such as nitric acid and hot, concentrated sulfuric acid. These stronger acids can dissolve copper over time.

Interestingly, when exposed to the elements, copper develops a greenish coating called copper (II) carbonate, which acts as a protective layer against further wear. Unlike most metals, the green oxidation that forms on copper is often a desirable finish, adding to the aged look and natural patina. 

Here’s how it works:

When a current is applied, copper ions migrate and deposit onto regions with a pre-existing metal seed layer, usually cyanide copper base.

Process:

• The workpiece (usually steel, aluminum or its alloys) is immersed in an electrolyte bath containing:
• Copper sulfate (CuSO ₄) as a source of copper ions.
• Sulfuric acid (H ₂SO ₄) for conductivity and charge transport.
• Additives like brighteners, suppressors, and levelers.

Purpose:

• Creates a shiny, smooth, and level surface on metal objects.
• Commonly used in automotive, plumbing, electrical, and computer parts.

The polished acid copper plating could be the final finish; however, it is more often used as the base for subsequent finishing processes. These include mirror buffing prior to other operations such as nickel or chrome plating.