Aluminum alloy is widely used in various industries, due to its lightweight and good mechanical properties, and anodizing is one of the commonly used surface treatment methods for aluminum alloy. It can greatly improve the corrosion resistance and aesthetics of the aluminum parts. However, if the aluminum alloy part is anodized after welding, the anodizing color will be uneven.
In this article, we will analyze the reasons for the anodizing color variation of a welding aluminum alloy part, and find out the solution to minimize the color difference. Let us dive in.
1. Welding Rod or Filler Alloy Factor.
The welding rod is a different alloy from bulk material. The welding seam is a different alloy from the rod and bulk material. Also, the area around the welding seam is now a different alloy from the rod, bulk material, and the welding seam itself. The different chemical ingredients in the aluminum alloy will lead to color difference after anodizing.
In this case, choosing the right welding rod or filler alloy is very important. Take
the Al-6063 for example, to get a good anodizing color match after welding, you can use Al-5356 as filler alloy.
2.Reason for Oxidizing Reaction with the Oxygen in the Air.
In the welding process, due to high temperature, the oxygen in the air will react with aluminum alloy and create the oxidizing layer, the oxidizing layer thickness
is uneven, resulting in the color inconsistency of anodizing.
In this case, to reduce the formation of the oxidized layer, we should clean the surface of aluminum alloy before welding, and also, use inert gas to protect the surface from reacting with oxygen.
3.Welding Deformation and Residual Stress Effect.
Heat deformation and residual stress will be generated during the welding process, which will change the grain structure on the surface of the aluminum
part, thus the chemical ingredients on the welding seam are different from the
rest material, leading to color difference after anodizing.
To reduce the welding heat effects, it is necessary to choose the suitable welding technology and welding parameters to reduce the residual stress, and also use anneal treatment to eliminate the residual stress further, in the anneal treatment,
it needs to control the time and temperature, as well as the speed of temperature increasing and decreasing.
4.Affect of the Overheated Zone.
Overheated zones will be created during the welding process, the oxidized layer
in the zone area will be thicker than that of the other area, it is one of the factors causing uneven anodizing color.
In this case, we should control the welding temperature and speed to minimize
the impact of the overheated zone.
5.Anodizing Parameters Factor.
Some of the anodizing parameters will affect the color, selecting the appropriate Electrolyte composition and concentration will help to maintain the anodizing
color consistency, and a suitable anodizing current will contribute to minimize
the anodizing color difference of aluminum alloy welding parts as well.
Conclusion:
To reduce the color difference of a welded aluminum alloy part, we should
choose the right welding rod/filler alloy, limit the welding heat generated to
reduce the overheated zone and heat deformation, protect the parts with inert
gas to minimize the oxidizing reaction and optimize the anodizing parameters.
Hope this will be helpful for you to reduce the anodizing color difference on the welded aluminum parts.
If you still have questions on the anodizing of welded aluminum alloy part, please don’t hesitate to contact us, we are happy to discuss with you about the solution.