Anodizing is a post treatment method in aluminum die casting and black hard anodizing will make an alloy somewhat corrosion free. Die casters offer post-treatment for original equipment manufacturers, but the end consumers may feel that any color can be mixed and matched whilst anodizing aluminum. However, that is not always true.
Black hard anodizing is a popular method in post-treatment of alloys but there are some factors that tend to influence which color should be used in anodizing of dyes as listed below.
The Types of Alloy
Aluminum oxide is porous and that absorbs to the dye forming distinctly colored anodized castings. However, alloy also plays a key role when choosing the anodizing color due to alloying elements that affect the aluminum oxide, which absorbs on the aluminum substrate. For wrought alloys, the weight percentage of zinc and magnesium may alter the aluminum oxide substrate’s tone drastically.
Coating Thickness and Anodize Types
From Type II and Type III coatings to the industry standards such as MIL-A-8625F, there are different anodize types which die casters choose in anodizing. Generally, metal is being exerted with thick coatings, temperature, concentration, and density in anodizing.
Type II coatings have a transparent, thin, and porous film, that is ideal for cosmetic applications. The porous film will absorb dye quite easily, and due to that, color matching will be relatively easy with Type II coatings in anodizing.
Role of Pre-Treatment
When trying to meet the end consumers color standard, the bright and the matte finish will play a role in anodizing. Certain alloys have limits, but the product manufacturers in aluminum die casting often find a way to customize the pre-finish of the alloy so that they can achieve a bright or matte finish later.
Alloys with certain elements need little to none exposure to the harsh caustics and acids due pre-treatment, and that will avoid quality issues associated with anodizing. For instance, a mechanical finish such as tumble or polish is a far better option than chemical exertion.
Another factor to consider in anodizing is light fastness. As distinct dyes will have varying color fastness, that will affect how fast the dye fades when exposed to sunlight. In such cases, die casters will choose optional dyes for colored anodizing.