Tuning Corrosion, how to avoid?

[airgun14]

After spending like 5 days going threw my pcp guns, specially open up the tubes and inspect them and change o rings, Ive noticed there was some small corrosion in some part where aluminum meets brass, it was green in color, i did manage to get the most away,,,, is there a way to prevent this happeing again (except filling with dry air of course), some lube, some spray? I did put a thin coat of silicon FX Lube, but not sure if this will prevent anything?

Not sure for example why Hatsan BT 65 have aluminum and brass in their tubes, Ive also noticed some green corrosion inside where the brass valve fillingport meets the spring... so it seems brass and some steel is not so good friend either..



Have not seen this problem in Hatsan AT44 Steel tubes

 

[MacGyver]

Galvanic corrosion with dissimilar metals is a common issue. While moisture certainly exacerbates the problem, I'm not sure even a dry fill will completely abate it.

 

[nugria]

Hi,

Eliminate the electrolyte and galvanic corrosion goes away. Moisture (water) may be the most common electrolyte but may not be exclusive. Hopefully the compressor oils don't have acids. Oxidation is rather hard to control unless you exclude, well, oxygen. I'd guess that what you are seeing in the air tubes is galvanic corrosion. I've got machined assemblies with dissimilar metals on my desk that are > 35 years old and they still look just fine and I work in the subtropics right on the line with the tropics.

FWIW,

Nugria

 

[MacGyver]

Good info.

I have considered moving over to dry nitrogen and keeping the compressors as a backup. It just doesn't seem as convenient when it comes down to filling bottles to take with you, etc.

 

[KatoKevin454]

Maybe try installing a Sacrificial Anode, a small piece of zinc to the metal surface, in theory it should corrode from the electrolysis and keep other metals from corroding.....

 

[airgun14]

good info, I think the key is to open up the tubes once in a while, keep them clean and dry, then add a small tiny amount of some protector to keep water away if it ever gets inside.

I will keep sight inside my tubes for sure, in this case it was just very small amount, so really nothing, but it is good to have this things in mind also..