Hi everbody, I am wondering if anybody knows which aluminum material is more resistant to corrosion a390 die cast material or 6061 extruded material. Thanks Mark
It will depend on quality of casting (i.e. surface porosity) and surface treatment (alodine, anodize, paint,...) and if there is a presense of salt, other chemicals, more than the substrate material.
Corrosion from what??? There are some variations with alloy, but in general a wrought aluminum (i.e. extruded, rolled, etc.) will have a much finer/consistant/orderly grain structure arrangement to resist corrosion better. Almost all porosity, even at the grain structure level is eliminated. A casting always has bigger grains and porosity. Casting corrosion can be deep, pocketed, and assisted by air pollution. Wrought corrosion is usually just a whitish skin. Check out any old window frame or screen door frame. Aluminum is an EXTREMELY REACTIVE metal. The surface reacts with oxygen in microseconds, but the oxide layer is only a few molecules deep, forming a protective skiin. When you anodize, the skin of oxide becomes much thicker, for more resistance to corrosion. Castings are usually not anodized, but there are other surface treatments available.
What is the application? Both materials have good resistance to corrosion in the general sense, but in certain atmospheres both can see corrosion damage. In general, the choice between A390 and 6061 is defined by the process being used.
