WOW... corroded parts in a Benjamin Maximus...

[TKO22]

After 15 years of tuning and resealing Benjamin Discoverys and then Maximus rifles, I would say this is the worst corrosion I have seen inside an airgun of any make. The gauge port had metal starting to "sponge" and crumble.

These came out of a rifle that was relatively new, and hand pumped. Owner is in a Gulf state , so I can only surmise that salt air moisture was being pumped into the gun.

The fill adapter had some corrosion but cleaned up nicely.

This valve is usable, but the gauge port was replaced. The tube had slight corrosion in it but I was able to hone it out without much effort or taking really any metal out of it.

I have started seeing similar corrosion (just not as bad) in much older Discovery rifles, but the newer Maximus rifles I've resealed haven't had much til now.

[lizzie]

Moving to the Darkside (PCP)

[FuzzyGrub]

It looks like most is on the non-pressurized parts.  ie it didn't come from pumping, mainly from the direct environment.   

[customcutter]

Any pics of the inside of the cylinder, or pressurized parts?  Looks like on of Swamp Peoples guns.

[Ribbonstone]

John is right….ambient pressure areas.  May as well check the fill cap from it’s sealing o-rings forward too.

Definitely a new gauge block. Might salvage the valve, at least as a spare, depends if the corrosion got under the o-ring seat and turned it rough and crusty (which it did on one end of the gauge block).

[Pellethuntr]

I recently took my Discovery apart for a rebuild and had a similar but definitely not as bad experience. I bought the gun when they first came out and it has been used and abused ever since. It was filled with a hand pump until last year. It has shot countless tins of pellets and spent many years in my unheated shop or in my truck. I cleaned it up good and made sure to lube everything well be for reinstalling. I fully expect to get another 10+ years of reliable daily use out of it. I'll keep rebuilding and hunting with it until it is no longer safe to do so. To me this particular gun is a tool and it has a job to do.

[Ribbonstone]

Just a suggestion that’s worked for me.   Clean tube, clean parts, with a thin coating of “real” silicone grease coating tube and parts before you reassemble.

[Motorhead]

Galvanic corrosion 101 case right there 

Read: https://r.search.yahoo.com/_ylt=AwrWjWL4ki9iyA4AABAPxQt.;_ylu=Y29sbwNncTEEcG9zAzEEdnRpZAMEc2VjA3Ny/RV=2/RE=1647313784/RO=10/RU=https%3a%2f%2fmetalprofy.com%2fblog%2fhow-to-prevent-galvanic-corrosion-between-aluminum-and-steel%2f/RK=2/RS=ltWrLMcVdv4QZXd3TRDYb.21ZN0-

[FuzzyGrub]

Most of crosman's other pcps use anodized valves.  But, even with them, I do as RS, silicone grease the surface.  Create a barrier. 

If shooting allot in high humid conditions, causes a cooling of the air tube, which attracts condensation.  That moisture becomes the electrolyte, between the steel and aluminum.