N/A Internal corrosion

[Caliber 22]

I am working on an old rifle here:

FX - FX Typhoon loosing power

Somebody asked me to help him with his Typhoon that lost power. I did not see the rifle yet and prepare to replace some O-rings. What is the most common reason for the Typhoon to loose power? It is a 5.5mm full power rifle. The owner is not technical minded and cannot tell me anything but the...

www.airgunnation.com

I just thought about this: The owner was using the rifle since he bought it new about 22 years back, together with a hand pump. It is now the first time the rifle was opened since new. He always used the hand pump and that without any moist filter of any kind. I did not see any corrosion on any of the internal parts of which some are bare brass and other aluminium. With my own rifles I fill with a hand pump I did not see any corrosion.

I saw some pictures in the past about heavy corrosion on mainly internal brass parts. Will that be because of some acid in the air in some areas with high air pollution? I live in an area, on a farm, far away from big industries or other polluting sources but the owner in a highly populated area but still not big industries.

I think it has a lot to do with air quality. What do you say?

 

[rcarlisle]

My take is that a hand pump does not produce moisture as fast as an automated pump. Far more important to have a moisture trap when using an automated pump as they are going to pull moisture out faster because they are generally compressing faster. I've hand pumped exclusively since I got into PCP airguns (a good 10 years now) without any evidence of moisture in any of the tubes. I haven't bothered using any inline filters. Stopping every 40-60 strokes, bleeding the line and letting everything sit a few minutes goes a long way to keeping the internals dry. On the plus side, most people are gonna want to take a break around then anyway.
Edited to add that once you have moisture in the tube, you're going to get that kind of corrosion where two different metals are making contact, for instance brass and aluminum.

 

[Caliber 22]

I do it that way as well, apart from bleeding between pump sessions. The owner of the Typhoon I am working on is now 72 years old and he is pumping his rifle in one session without rest in-between. I assume moist is going through but does nothing negative to the rifle.

I wonder if the composition of the brass has anything to do with it? Maybe less zinc and more copper cause more corrosion ?

 

[rcarlisle]

I'm betting he's just not pumping fast enough to actually produce precipitated moisture in a quantity sufficient to get out of the pump and into the rifle. Most hand pumps have a reservoir that collects moisture as it precipitates from the compressed air. If you aren't filling that cup during the pumping session, it should blow out when you vent the pump to remove the hose. There's probably still a bit of humidity in the compressed air inside the tube, but it would only be a problem if it condensed.

 

[Rawroots]

Gradual temp changes slows sweating, quick temp changes definitely causes moisture, my friend always uses a gun case until temp normalizes to inside outside temps, here in michigan it makes sense to me.

 

[bchannell]

There are so many variables in moisture problems.
1) Location, do you live in an extremely humid loacation? That will affect moisture getting into your guns.
2) How you fill. This covers a lot of ground. Is the gun above the low point of the fill hose? That can keep moisture from "rising" to the gun. Do you have a cotton filter to stop liquid from moving into the gun? Do you use desicant? Do you fill fast or slow, take breaks, etc?
3) What do you fill with? A hand pump is hard to pump fast enough to build up substantial heat and precipitate moisture in a large volume. Do you use a slow compressor Ie., a GX or similar? They don't fill fast and build a lot of heat. Does you compressor have any moisture mitigation built in?

That's just a few of the problems that can crop up. The truth is, and combination of them can cause problems, but all can be mitigated should the need arise. I filled with a GX for a long time, and never had moisture in any of my guns. I live in WV where moisture is not a big deal, so that's likely the saving grace. I now use N2 fed to a GX and that works like magic and no, absolutely NO moisture, so no worry.

If it's me, I would choose a method of pumping up my gun ie. hand, compressor, scba, whatever, and then use it and check my gun for moisture from time to time and let that be my guide on filters, and moisture mitigation. You can't argue with results.

 

[Caliber 22]

1) Location, do you live in an extremely humid loacation? That will affect moisture getting into your guns.
2) How you fill. This covers a lot of ground. Is the gun above the low point of the fill hose? That can keep moisture from "rising" to the gun. Do you have a cotton filter to stop liquid from moving into the gun? Do you use desicant? Do you fill fast or slow, take breaks, etc?
3) What do you fill with? A hand pump is hard to pump fast enough to build up substantial heat and precipitate moisture in a large volume. Do you use a slow compressor Ie., a GX or similar? They don't fill fast and build a lot of heat. Does you compressor have any moisture mitigation built in?

1. I live in a humid area but not extreme.​
2. I use a hand pump with pump and rifle on the floor at same level and do 50 pump strokes then stop for 10 - 15 minutes. The pump have a desiccant tube on the inlet side and there is a cotton filter on the whip. The desiccant is blue when dry and pinkish when moist. As soon as the blue disappear which takes about 3 - 4 times filling the rifle, I dry it in the microwave oven.​
3. As #2 above.​

As for the owner of the Typhoon I am working on, he lives in a less humid area. He also use a hand pump, flat on the floor with the rifle. His pump has no desiccant and no cotton filter. So I guess that after more than 20 years of using the same pump on the same rifle, he must get some moisture in the rifle in the rainy season but it does not have an effect on that rifle.