Oxidation of stripped alox?

papercut · **on:** January 31, 2014, 04:39:37 PM

Hello there, I recenfly bought a China sak with non ferrous seemingly aluminum or aluminum oxide scales that have some sort of black coating- it could be anonoization. A modder has it right now and we are considering stripping it of the coating. He has the following comments so far:

I got the black alox apart, I tried some mild abrasive on the logo, it turned silver. it is most-likely stamped on, dried or baked then they anodize it, heat won't even blister the alox. Oven cleaner might be the best bet (in glass, outside). Just built a custom 91mm Ranger (without scissors & Hook) for a retired Park Ranger. Turned out really nice for a 4-layer.

I found this on a bike forum:
If it's solvent based it's safe, if it's alkali based, DON'T DO IT - aluminium oxide dissolves in strong alkalis. Test? Put an anodized bike part in caustic soda (lye?) and the colour can be rubbed right off :eek:.

Chemicals that eat aluminum: Drain-O, Possibly concentrated Lysol (Alkyd).

end quote.

He is concerned that stripping the scale of coating will expose it to oxidation, but we are not sure of the scope of thus oxidation. Any thoughts?

Syph007 · **Reply #1 on:** January 31, 2014, 04:44:45 PM

Bare aluminum will oxidize yes, but slowly. Thats one reason to anodize it to protect the surface. When I use lye to remove stock Vic anodize, the result is not a shiny surface, I have to sand and polish the edges to restore a good surface for re-anodize.

Not knowing what those scales are though I wouldnt assume anything. I highly doubt they are quality aluminum 6061 T6. You can tell by feel though, if they are light weight and 'ping' when struck, they probably are.

papercut · **Reply #2 on:** February 04, 2014, 10:34:49 AM

Well, I have a collection of seen better days alox. Some of it I think would be considered oxidized a bit. Are there any steps that can be taken in slowing down/stopping the process? I remember reading about soaking Saks in vinegar somewhere.

Cheers

PTRSAK · **Reply #3 on:** February 04, 2014, 11:25:00 AM

mmm pickled Alox.

Aluminium is funny stuff, it is actually quite a reactive metal, but relatively quickly forms a quite hard oxide layer that slows further reaction (oxidation).
Anodizing actually forces this oxide layer to be thicker and harder than "natural". This however is only completely true for pure aluminium.
When you start to talk alloys things go a little haywire. Some alloys are actually more corrosion resistant than pure Al, but most higher strength alloys corrode readily. Particularly the 2000 and 7000 series where the primary alloying metals are copper and zinc.
If not protected these tend to suffer intergranular and then exfoliation corrosion. Contact with dissimilar metals can make the situation even worse.

I used to see a LOT of corrosion working on airplanes., like this...

I have seen panels coming apart like puff pastry.

dks · **Reply #4 on:** February 04, 2014, 12:31:04 PM

In Swiss army knives (wenger/victorinox) the outside layer at least, the oxidised/coloured Alox one, is also hardened adding protection from scratches as well as from oxidation.

They are actually harder than the blade, from what I recall

.