Our research shows that IVD aluminium vacuum coating is widely identified as the high-quality alternative to the use of cadmium for corrosion protection, because it combines limited levels of added layer and comparably low life costs with a satisfying duration of protection.
In terms of accelerated corrosion tests IVD aluminium exceeds the performance of cadmium: 25 to 50ums of aluminium (a class 1 type II coating) will pass the standard 672 hours salt spray test and typically exceed 1,000 hours. Thinner coatings, that can be specified for close tolerance or threaded parts, will easily exceed the specified 336 hours for comparative cadmium coatings.
Hard anodizing produces a relatively dense, thick oxide layer. As a result, the film tends to be darker in appearance although the final colour is largely dependent on the alloying constituents (elements) of the base material and, in its natural state, can be anything from light green/gold to dark grey/charcoal.
Hard anodizing has become a very important technique where weight saving (e.g. by replacing aluminium with steel) combined with good corrosion protection and wear resistance are required. Furthermore, unsealed anodic coatings can absorb and retain oil when used on sliding surfaces for cylinders and pistons etc., providing longer lasting lubrication.