Chrome-free conversions
The problem is with chromate conversion coating (sometimes referred to trademark names, Alodining or Iridite). It is method to process aluminium to assist in superior corrosion resistance. Other advantages are its hardness, golden colour, self-healing characteristic, thermal conductivity and electric conductivity. The issue is that it is environmentally hazardous and carcinogenic. Our product needs to comply with European standards (and you know how hectic that is).
My research to date (in brief) is as follows (listing advantages and disadvantages):
Cr(III)
Adv: Similar properties.
Dis: Different colours. May need additive/top-coat for increased corrosion resistance. More expensive.
Sn-plating
Could not find descent information yet, but it is electrically conductive
Anodizing
Non-conductive
Other alternatives
Molybdate-based coatings
Organic Films (non conductive)
Inorganic Salts eg phospating (weak corrosion resistance)
Organometallics (very expensive)
There is a good paper which discusses chrome-free coatings (ASTM B921), but I cannot spend S50 on that at the moment.
What I wish to discuss is RoHs compliant alternatives as well as
You never want to use pure tin...look up dendritic growth.
See this for some ideas
http://www.google.com/url?sa=t&sourc...BnJrJzJbexoFiA
Tin whiskers - wow! I never knew, but a very interesting phenomenon. Thank you very much for your advice and that article. It thoroughly] answers my question.
I am not the biggest forum person, so I am not sure if anybody would be interested once I found the most effective solution to this problem. If so I am certainly willing to post my findings here (it may still be a week or two though).
Sure, post away. I know there are lots of new environmental laws, but don't know what the modern solutions are to the corrosion problem. Remember, for microwave use, any "conversion coating" you use has to be pretty conductive electrically.