Can anodized parts outgas corrosive sulfur vapors?

A. Analyze (EDX) any anodized coating, and you will find sulfur. Personally, I don't think there's any way to avoid it, only minimize it. This is obviously accomplished with adequate and thorough rinsing after anodizing. Proper rinsing is often overlooked when designing an anodizing line. I'm pretty sure rinsing is what Brian was zeroing in on when he asked you questions about your process. If it were me, that would where I would look first, along with the environment that the part is exposed to as an end product.

A. Hi Manju,

Extruded aluminium isn't known for retaining sulfuric acid. You would probably have noted some "white spotting" if there was trapped sulfuric.

Realistically if the parts were anodized, rinsed, dyed and sealed properly the chances of subsequent sulfur corrosion should be minimal.

If you still think the anodized part may be the source of the contamination then you need to have a newly anodized part analysed. There will always be residual sulfur in any analysis, this is usually as aluminium sulphate, not as free sulfuric acid. A simple thing you could try is to wash some parts in cold water and measure whether there is any change in pH, if there is any residual acid left you would see the pH drop from its original number (a bit of a rough and ready test, but at least somewhere to start).

Of course if you find no residual sulfuric acid in the coating then you will need to look for other sources of corrosive materials.