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Magnesium vs Zinc for nickel acetate seal

 

I work for a bulk anodizing company that uses nickel acetate seal tanks (among others) with Magnesium bars in the tanks to keep corrosion resulting from stored electricity from damaging the parts. I'm wondering if anyone can tell me what the benefits are for using Magnesium instead of Zinc, as it seems that zinc would be a lot easier to get a hold of. Also, does anyone know of a good supplier of Zinc or Magnesium bars?

All answers are greatly appreciated.

Jim Gorsich
Compton, California, USA

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You use magnesium as it stops galvanic corrosion by being more reactive than the aluminium.

DO NOT USE ZINC - it is less reactive than aluminium

(electrode potentials - mg2+ to mg -2.37V al3+ to al -1.66V zn2+ to zn -0.76)

If you do use zinc you could well get your work pitted.

Other answers are to insulate the flight bars from the tank with is quite a job due to the steam.

As to where to find magnesium, we got some from a customer who messed up machining a helicopter gear box, ask a few customers they might have some scrap you could have.

Martin Trigg-Hogarth
surface treatment shop - Stroud, Glos, England