Alocrom 1200 (also known as Bondorite or Alodine in the USA)
This is the best and most reliable form of chemical conversion coating for aluminium and works well on all aluminium alloys and is not dependent on specific compositions.
It gives excellent corrosion protection and substrate for subsequent application of paint and adhesives. The coating has low electrical resistance and can be used to repair anodised coatings and refresh them before painting.
Alocrom is preferred for difficult high-silicon pressure die-castings after careful cleaning.
Can be used as either class 1A (maximum corrosion protection) or class 3 (low electrical conductively).