Don’t Let This Happen To You!

Tuesday, December 18, 2018

Don’t Let This Happen To You!

It’s PCP airgun corrosion – this is what moisture does to your air rifle…

It’s widely known – or at least fairly widely – that PCP airgun corrosion is caused by moisture in the air that’s used to fill an air rifle. But what does this PCP airgun corrosion look like and how bad really is the damage?

These photographs show how bad the corrosion actually can be. Look and be warned!

Don’t Let This Happen To You!

Above. There’s plenty of corrosion on this Marauder fill adapter. You can also see oxidization build-up on the sintered filter.

Note that our photographs happen to show corrosion in Benjamin and Crosman airguns. That’s because these are examples seen at a Crosman Repair Center. But every PCP airgun – not just Crosman/Benjamin models – suffers from this problem.

You can find PCP airgun corrosion in any make of airgun!

Every time you fill your PCP airgun without a dessicant system of some sort, you are causing this problem. You’re actually pumping water vapor – moisture – into the gun every time you fill it with High Pressure Air.

The result is long-term damage to your gun and an expensive repair bill just waiting for you in the future!

Don’t Let This Happen To You!

Above. Here’s corrosion on a Discovery gauge port. It’s even inside the gauge adapter (arrow)…

Over the long-term – say 3 years or more – PCP airgun corrosion will be the number one cause of failure for PCP air rifles.

First, you find that your favorite PCP is starting to loose pressure between uses. Then the pressure loss becomes more rapid. Then, finally, the gun will no longer hold pressure.

If you have been filling with “wet” air – that is air that has not been passed through some sort of moisture-removal system – it’s guaranteed that this problem will be caused by PCP airgun corrosion.

Over the course of time, that water vapor inside your air rifle will cause corrosion.

The problem will be worse if you live in a naturally-humid area. It will be worse still if you live by the ocean – think salt water corrosion now. So if you live in – say – Florida and you’re filling your PCP with a hand pump and no dessicant system, your PCP air rifle WILL suffer from this PCP airgun corrosion!

There’s some evidence that PCPs with higher fill pressures – say 3,000 PSI and above – tend to suffer from this PCP airgun corrosion more than those with lower pressures – say 2,000 PSI. That makes sense, as the onset and progress of PCP airgun corrosion will most likely be worse the higher the pressure.

But what actually happens?

Yes, rusting of the HPA pressure tube is one obvious result. If a pressure tube shows any signs of internal rusting, it should be replaced immediately!

Below we have a view looking down a Marauder pressure tube.

Don’t Let This Happen To You!

You see, the O rings inside the gun seem to attract moisture like a magnet. The result is that rust occurs between the O ring and steel tube – usually in a circular pattern, exactly matching the location of the O ring.

I may be a coward, but the prospect of holding a rusty steel tube containing 3,000 PSI of air right next to my face every time I shoot doesn’t sound too clever. DON’T DO IT!

More surprisingly, perhaps, the majority of PCP airgun corrosion happens on Aluminum parts inside the gun, rather than the steel tube itself.

The high pressure moisture-bearing air causes the Aluminum to oxidize into a white substance. This white oxide then builds-up underneath the O ring seals inside the gun. But it doesn’t build up evenly!

Don’t Let This Happen To You!

Because the Aluminum oxide builds-up in peaks and troughs, eventually the rubber O rings inside the gun can no longer fill the gaps and leaking starts. It’s downhill all the way from there…

Prevention is better than cure.

The way to prevent – or at least massively reduce – PCP airgun corrosion is to ALWAYS fill your gun with “dry air”.

If you use a hand pump, make sure it is filled with a dessicant system such as this Hill pump has.

Don’t Let This Happen To You!

Alternatively, if you fill HPA tanks from a compressor, use a dessicant system – such as this Omega inline filter – between the compressor and the tank.

Don’t Let This Happen To You!

Or if you have your air tanks filled by a paintball store or dive shop, make absolutely sure that they are giving you dry air.

PCP airgun corrosion WILL happen to your air rifle unless you always fill it with dry air. Make sure that you only use dry air in your PCP.

Don’t let this happen to you!

5 Comments

  1. Gil Yost says:

    Very good advice …..joe Brancato touts the upright desiccant device…….any thoughts?

    1. I’ve not tested Joe’s system. But I do use the Omega Diablo Dry Air System and find that this works well.

  2. Tom Adams says:

    Great reminder! It’s nice to actually see the after effects of this situation. I also shared a link to this on AGN.

  3. ANich says:

    Great article, thanks, which is going to steer me away from this type of airgun, (which was otherwise looking quite interesting), but you do have to wonder how much would it add to the overall manufacturing cost to make these inferior interior parts out of SS? Maybe $5?

    1. Thanks for your interesting comment! To my mind the issue is actually not inferior quality parts in PCP airguns, rather the lack of widespread use of dessicant systems when charging these guns. I know of no manufacturer which is using stainless steel (your SS?) for all internal parts and guess that the additional material and machining cost could be quite extensive. Just my $0.02…

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