Aluminum electroplating
The application of galvanic coatings is necessary for the metal and its coating are harmoniously combined in the product. Electroplating is applied to aluminum to protect the part from rust, give it decorative properties or provide specific properties: the ability to solder, improve electrical characteristics, prevent thread galling, increase wear resistance, and improve rubber fastening.
For example, aluminum with such coating is suitable for aircraft construction, because it turns out to be durable and very light.
However, electroplating on aluminum is still not widely used. Because of certain difficulties associated with its application.
Aluminum oxidizes easily and becomes coated with a chemically resistant oxide. It seems that this coating makes it resistant to rust. But it is false. Just a few acidic substances drops may cause corrosion damages. This is clearly seen on aluminum car rims. If the paint on them is slightly damaged, then rust will certainly appear.
Aluminum electroplating methods
Since there are certain difficulties with aluminum galvanization, experts recommend using two methods for applying a metallized coating: chemical and electrolytic.
The first ensures that the coating is applied in all places where the solution falls. As a rule, chemical nickel plating is used. For example, this can be used to cover aluminum profiles. The solution will settle in all cavities, and even in places with poor eсcess. The main thing is that the solution has access to them.
Electrolytic treatment is a little more complicated than chemical treatment. The thing is that adhesion may be poor because of the difference in the depth of the baths. This means that the metallized coating will simply not be deposited on the product. Therefore, whatever metal is used for coating, it is important to perform nickel plating first.
It is necessary to constantly carefully monitor the thickness of the galvanic coating to be within the permitted standards.
How aluminum is electroplated
Aluminum galvanization begins with washing and cleaning the product. Then it is etched in several special solutions at a temperature of 70C. It is obligated to have a hood in the production for removing gas formation after the process. Typically, etching takes up to two minutes. More time takes etching of pre-anodized parts.
After that, the product is subjected to zincate treatment at room temperature, another etching in a solution without nitric acid, and again to zincate treatment.
Zinc treatment is necessary for a layer to be formed on the product, which is not passivated, but amenable to galvanization. This procedure also takes about two minutes.
Zincate treatment repetition after etching results in a denser and finer-grained zinc coating.
Further, the product is waiting for alkaline copper plating, acid copper plating, nickel plating and chrome plating.
It is very important that the etching of the part is of good quality. The fact is that if somewhere it was not etched away, then other layers of the coating will not fit well.
And everything can be fixed only by removing all the cover.
The material of the product plays a very decisive role in coating. You need to know for sure this is pure aluminum or its alloy. Pure aluminum is easy to process. The problem of alloys is that additional metals might leave on the surface of the product in the form of black and gray coating. And additional processing will be needed.
Therefore, before galvanizing an aluminum alloy it is best to test a small part for knowing the exact reaction to this procedure.
By the way, aluminum galvanic coating of products from other materials can also be produced. This happens in the same way as aluminum metallization.
