Are compressed air fittings supposed to corrode?

compressed air fittings
(Last Updated On: August 3, 2020)

I just took apart some older fittings. I was unhappy to find that though they still looked shiny on the outside, and on the quick connect side,  on the thread side, the inner passage was badly rusted.  The connects were labeled AMFLO C21.  I took apart several more and they were  also rusted.

Is this just a problem with this brand or is it common?

Do I have to take apart fittings one a year or so to check them?

Or should use I only Brass?

How long should a fitting last?

Or is this due to the fact that I had brass connected to non-brass?


The vast majority of compressed air fittings are made of brass, stainless steel, nickel plating and composite plastic.

Rarely is an air fitting made of plated steel, as the end result will be just what you’ve described, erosion of the plate and corrosion of the underlying metal.

I’m not going to comment on the product you refer to, as I’ve never used it.

What I can tell you is that you MUST buy brass or nickel plated brass fittings for use in compressed air systems. If the fitting is a composite, the body being made of high impact plastic with metal components, those metal components must be brass or nickel plated brass.

I’m not sure why the major air fitting manufacturers all seem to plate the brass portions of their fittings with nickel. Is it appearance, improved flow characteristics…, there is a reason, as they wouldn’t add the cost of nickel plating to the cost of manufacturing the fitting if it weren’t deemed necessary.

In any case, whether the brass is nickel plated or not, these fittings won’t rust, even if the plating gets abraded on the inside by air, water and particulates passing through them at cyclonic speed.

That you have a rust problem in your fittings tells me that you’ve somehow acquired a plated steel fitting, and as far as I’m concerned, that’s a no-no.

It’s my suggestion that you visit an industrial compressed air equipment shop and buy your couplers, connectors and fittings from them, making it clear that you want only industrial stainless steel, or nickel plated brass fittings. That will solve your corrosion problem.

And no, if you use the correct fittings, you won’t have to take your air circuit apart and examine the fittings every year or so. In a typical, non-dynamic compressed air installation, the fittings should last for decades.

Hello, I am Bill, the Compressed-Air-Man. I have years of experience in industrial and residential compressed air applications, air compressors and general pneumatics. I created this site to help professionals, students, and DIYers understand and properly implement and maintain compress3ed air systems.


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