CastProtect™

Die casting is widely used as an effective method to very cost-effectively obtain a mould with good physical properties. Unfortunately, the properties that make injection moulding complex shapes and low cost mean that the traditional anodising process does not provide acceptable corrosion resistance in higher corrosion applications. Die-cast alloys contain high levels of silicon (Si), iron (Fe) and copper (Cu). Silicon is more than 20 times higher in these castings than in wrought alloys. The properties that make die-cast alloys and the associated production process economically attractive to the manufacturer/copper also make the alloy less suitable for anodising than wrought alloys.

Research by, among others, the Aluminium Anodiser's Council indicates that layer thicknesses of up to 12.7 microns can be achieved on cast alumium. Additional research also shows the presence of voids in the anodic layer directly related to unalloyed, elemental particles of silicon and copper. The results of the layer on machined surfaces are higher than on cast-only surfaces. The latter is the main reason why salt spray test results for anodised cast parts are lower than comparable anodic layers on ductile alloys.

The photos above show 2 cast aluminium products. The product on the left is anodised to MIL-8625 Type II as standard. Once placed in a high corrosive environment, the deterioration is clearly visible. The one on the right has been treated with the CastProtect™ process and then placed in the same corrosive environment.