AL 6005 and 6351 corrosion resistance differences 1

[TRRMan]

Does any one know if there is a difference in the corrosion resistance between 6351-T6 and 6005-T5 Aluminum. This product is used in the transportation industry and will come into some contact with water and salt easpecially during the winter. Thanks for any help.

 

[kenvlach]

Whichever one is anodized, epoxy primered & polyurethane topcoated will perform better.

I don't know of any corrosion testing directly comparing these 2 alloys; possibly the auto companies have data.

General rules for corrosion of aluminum alloys include
1) The purer the Al the better, so 6005 should be better than 6351, both bare & anodized.
2) Worst alloying element in terms of corrosion is Cu (both have max. 0.1 %), then Fe (6005 has max. 0.35%, 6351 has max. 0.5%).

Mg & Mn can be higher in 6351 and may have a positive effect, but maybe canceled out by Si. The temper doesn't matter nearly as much in 6000 series as in 2000 & 7000 alloys. So, my guess is 6005 is slightly better vs. corrosion, as well as slightly brighter anodized.

You may find these brief presentations interesting:
'Corrosion Control of Aluminium - Forms of Corrosion and Prevention,'

http://www.eaa.net/education/TALAT/lectures/5103.pdf

and
'Basic Approaches to Prevent Corrosion of Aluminium'

http://www.eaa.net/education/TALAT/lectures/5104.pdf