I am anodizing a 13 mm x 5 mm piece of aluminum in citric acid + phosphoric acid + ethylene glycol with a carbon counter electrode. I want to limit the exposed region of the Al piece, so I cut a slit into the top of a rubber stopper to put the Al into, and cut a window into the side of the stopper to expose a region of the Al.
By limiting the exposed area of the Al, I expected to see a reduction in the current passing through my cell. Instead I saw in increase! I also saw bubbles forming all over the rubber stopper, similar to the bubbles that form on the carbon counter electrode during the reaction.
Does this mean my rubber is conducting current and reacting with the solution? this seems very strange to me, as rubber is such a good insulator...
Any ideas?
Hi,
first of all AUTOLAB company sells special holders made of polypropylene.
I anodized aluminum in such a way: first I electropolish the sample, next I am drying it and covering its back and edges with acid resistant dye. It works!
What dye do you use and how long does it take to dry? How do you apply it? Thanks for the FYI on the AUTOLAB holders, I will check that out.
It takes one day do get dry. It is a typical acid resistant dye for metals. You can use a typical dye applied in automotive industry.
this approach prevent aluminum from corrossion succesfully.
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