Letter 24120

Corrosion Rate of Alodined magnesium  

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Currently we have a PDA frame made of Magnesium AZ91D finished with Alodine 5200 coating.
Will like to find out what is the corrosion rate when coated with Alodine 5200.

Jeremy Ng Yong Khim
electronics - Singapore

How are you! Alodine 5200 is non chrome conversion coating agent. I did test before. I found poor result of salt spray than generally chromate coating. I think non-chrome conversion coatings on Al,Mg have a lower resistance than chromate coatings.

SE DO JANG
- Korea

Jeremy,

What is the environment for this component? As Mr. Jang said, Alodine 5200 does not provide good resistance to corrosion in a salt spray environment. However, it may provide adequate corrosion resistance in normal ambient environments (humid air, low salt, etc.). Alodine 5200 is usually used as a pretreatment prior to painting. The combination of Alodine 5200 with either a cathodic epoxy electrocoat (e-coat) or a polymer powder coating (epoxy or polyester) can provide resistance to corrosion in salt spray environments. Damage to the relatively thin e-coat layer can produce premature corrosion. Thick powder coatings usually provide much better corrosion resistance than just e-coat.

Toby Padfield
- Michigan