Methanol reaction with aluminum

[sciguyjim]

I saw the following post on another forum and can't explain it...

"A word about using methanol around aluminum. Here at work we have high pressure liquid chormatography systems that use methanol as an eluent. We were having problems with the system and it turned out that the methanol was eating away at the aluminum pump heads. Filling a beaker with methanol and submersing the head gave a rather interesting result. The head fizzed as if in hydrochloric acid turning the liquid gray with dissoved metal. This was at room temp. It could be even more corrosive at high temp and pressure."

Now, I've heard about methanol reacting with powdered aluminum but not massive metal. Can anyone explain what might be going on? I think he may have something in the methanol he doesn't know about.

FYI, I found this methanol MSDS on line (typical of others i've seen):

"Materials to avoid:

METALS

(e.g. powdered aluminum or magnesium) - mixtures can detonate, with more power than military explosives.

Corrosivity to Metals:

Methanol is not corrosive to most metals. Admiralty brass, high silicon iron, naval bronze, nickel-resist and silicon copper have excellent corrosion resistance (less than 2 mils (50.8 um) penetration/year), while carbon steel, types 304/347, 316 and 400 stainless steels, copper, brass, bronze, ***aluminum***, nickel, lead, tantalum, titanium and zirconium have good resistance (less than 20 mils (505 um)/year)."

Maybe the pump head was not pure aluminum?? Anybody have any guesses?

 

[TVP]

Aluminum loses its passivity at pH levels exceeding ~ 8.5 At a pH of 10-12 substantial corrosion can take place. Aluminum and its alloys resist most alcohols, however, some alcohols like methanol can be very corrosive when extremely dry, especially at elevated temperatures.

 

[sciguyjim]

Ok, but RC airplane entheusiasts don't have any trouble using methanol fuel in their aluminum plane engines. The cylinders are usually lined in some way but the whole engine gets hot and the fuel inlet and outlet are bare aluminum.

RC plane fuel also contains nitromethane and lubricant but until they're burnt they shouldn't affect the pH.

Someone else said they heard that methanol is least corrosive to aluminum when it contains 1-2% water, no more , no less. That's all he could say about it.

Still sounds like there may have been something mixed in with the methanol.