Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
aluminium corrosion product
- Thread starter aybee
- Start date
The mil spec for chemical corrosion removal compounds for Al. is Mil-C-38334. A web serch under that number finds several suppliers for the product, to that spec. If the part is just stained you could likely remove it mechanically with scotchbright. The following site gives more details.
The MIL-C-38334 removal agent is phosphoric acid based, which actually removes aluminum.
I recall that we tried to remove aluminum oxide in our processing once and wound up using an ion mill to literally blast the oxide off, since it resisted all of our chemical etchants.
The MIL-C-38334 compound is relatively mild, so you'll probably need to wire-brush or grind off the majority of the corrosion, treat it with MIL-C-38334 compound and then anodize the surface to prevent or minimize future corrosion
TTFN
I recall that we tried to remove aluminum oxide in our processing once and wound up using an ion mill to literally blast the oxide off, since it resisted all of our chemical etchants.
The MIL-C-38334 compound is relatively mild, so you'll probably need to wire-brush or grind off the majority of the corrosion, treat it with MIL-C-38334 compound and then anodize the surface to prevent or minimize future corrosion
TTFN
Here are two materials that I have had great success with on Al around salt water. I would get a tube of both Autosol and Semichrome. If the link doesn’t work go to the home page and search for Semichrome.
If you have to use an H3PO4 based material the best would be from a chemical supply store. I would try one made for Al fins first. Get the concentrated variety, this will allow you to use higher concentrations if the white rust is heavy
Come back with whether it’s pitted or not.
If you have to use an H3PO4 based material the best would be from a chemical supply store. I would try one made for Al fins first. Get the concentrated variety, this will allow you to use higher concentrations if the white rust is heavy
Come back with whether it’s pitted or not.
- Thread starter
- #6
The best solution (in terms of not harming the aluminum substrate) is the 2.0 wt% chromic acid + 3.5 vol.% phosphoric acid, balance DI water, solution used at 50-100oC. This is the official method of stripping oxide to determine the anodic coating weight per ASTM B137, ISO 2106: 1982, B. S. 6161: part 1: 1984, and EN 12373-2: 1999. Sometimes called “slow stripping” solution, although actually quite rapid at 100oC. The chromic protects the bare Al from the phosphoric.
The next best method is to use a commercial deoxidizer/desmutting solution. These are either nitric or sulfuric acid based, but contain inhibitors to stop the attack when bare Al is reached.
Concentrated nitric acid (67-70 wt%) is also very safe for cleaning Al (pretty harmful to humans, though). A protective nitrate forms once the bare Al is reached. Dilutions to 50 vol% (38 wt%) are commonly used to reduce the nitric acid fumes, but the reactivity vs. Al goes up fast if the water content is increased. Useful for stripping metallic plating, too, e.g., EN (electroless nickel).
If possible, take your part to a nearby anodizing or plating shop, as they already have the above solutions and can safely handle.
The next best method is to use a commercial deoxidizer/desmutting solution. These are either nitric or sulfuric acid based, but contain inhibitors to stop the attack when bare Al is reached.
Concentrated nitric acid (67-70 wt%) is also very safe for cleaning Al (pretty harmful to humans, though). A protective nitrate forms once the bare Al is reached. Dilutions to 50 vol% (38 wt%) are commonly used to reduce the nitric acid fumes, but the reactivity vs. Al goes up fast if the water content is increased. Useful for stripping metallic plating, too, e.g., EN (electroless nickel).
If possible, take your part to a nearby anodizing or plating shop, as they already have the above solutions and can safely handle.
- Thread starter
- #9
thanks for all the input. I bought a litre of HF/Sulphuric acid Aluminium cleaning liquid from my local autospares outlet. It did work to a point I think the secret is in getting the dilution rate correct. used out of the bottle it ate the aluminium faster than the oxide, used per instructions (7:1 dilution)it was only partly effective..think it needed a lesser dilution and possibly warmer. I was amazed that I could by HF in the store , its very dangerous stuff and can kill in small doses when concentrated
- Status
