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Cleaning Aluminium/Magnesium Alloys


Dear All -

I'm an avid STM (shade tree mechanic) and one of my big problems is cleaning/degreasing aluminium/magnesium alloy parts. I have found that 'spirits of salts' (HCL?) actively cleans and degreases these parts. However, after this STM procedure the parts are 'blackened' and it's a real pain to clean off this black residue - currently a soft wire brush and lots of rubbing. Is there an easy (read chemical dip) way to get rid of this black residue? Or alternatively a chemical dip/mixture that cleans these parts like spirits of salts but leaves them nice and shiny?


William R Thomson
- Johannesburg, SOUTH AFRICA


I would switch to phosphatizing (use phosphoric acid) to avoid oxidation. Remember that you need a mild cleaner. Alternatively use a basic solution (NaOH) or ammonium base since aluminum alloys react at high or low pH levels. I would also stick with a known solvent made by a commercial supplier (ask your paint supplier!)

Kam Dianatkhah
- Dallas, Texas

April 25, 2012

Q. Hi! Folks, I'm Peter Ware from South Australia and wish to know what to clean Magnesium engine cases in as I'm told a caustic bath will dissolve it and am told hot water & Phosphate soap. But what is the best product to use and in what quantity, ratio to water etc. for best results. Cheers. Peter. PS Wish to bathe these cases.

Peter Ware
car restorer - Mannum. South. Australia.

April 25, 2012

A. You can try next solution: 30 gms sodium carbonate (washing soda) [affil. link to info/product on Amazon]/30 gms trisodium phosphate/1 gm synthetic soap/1 lit distilled water, pH 11, 80-95 C, 3- 20 minutes. Hope it helps and good luck!

Goran Budija
- Zagreb, Croatia

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