Rust eating away gold filter. Is it safe to use?

[ImpactX]

I took off my gold filter on my hatsan compressor. Inside is a cotton filter. I removed it and inside the gold filter there have been rust from oil and moisture. It seem like it's eating away parts of the metal filter. I use a pick to poke inside where the small rust are and its about 1mm deep. The tube is pretty thick but if rust is eating away the metal, is it safe to keep using? Hatsan doesn't even carry these big compressor anymore. So not sure if they even have replacement parts. I can contact them and hope they still have parts for it.

I heard aluminum doesn't rust. I thought these gold filters are made from aluminum. What are they made of and why is rust eating away the metals.

 

[bamavet55]

I was told that aluminum does not rust. However, aluminum will corrode.

Question: Is that gold colored paint on the metal?

 

[nervoustrig]

The first thing that comes to mind is possible galvanic corrosion. What is the cap made of? 

Galvanic corrosion can occur where dissimilar metals meet and become exposed to an electrolyte (e.g. water vapor and salts). The gold anodizing helps stave it off but anywhere the anodize layer has been compromised (scratched) is susceptible. That could explain the pitting just past the threads but if the discoloration at the bottom of the vessel is also pitting, I don't know where that came from.

 

[ImpactX]

Not sure what the cap is made of. But it looks fine. The bottle doesn't have a cap as it just screw into the base on the compressor. My concern is the expose part that lost the gold paint will get even more corroded as use and time goes on and maybe explode? Idk.

 

[nervoustrig]

The cap looks like it is very likely the same anodized aluminum. Can't be certain but that's how it looks. Thus the pitting is not likely a result of galvanic corrosion. 

So what is the next most likely cause? I don't know, maybe somehow exposure to an acid? Joe Brancato issued a warning a few years ago about the potential for molecular sieve desiccant to leach acid and attack aluminum pressure vessels. I can't vouch for the veracity of it but you can read up on it on GTA.
https://www.gatewaytoairguns.org/GTA/index.php?topic=104162.0

By the way, doubtful the finish is paint. Woe unto the manufacturer that would dare paint internal threads. 99.9% sure we are looking at an anodized finish.

 

[biohazardman]

I would agree with the anodized finish and likely that the molecular sieve got into the places that are corroded.

Anyway yes it will get worse but how much and how fast depends on how well you take care of the filter. Take it apart and clean it every couple/few months to make it lasts a bit longer.

The walls of the filter are quite thick, as you have said, but if the corrosion is 1mm deep it should be watched very closely.

 

[harrymoreland]

Idea, that may be debunked.

Plastic sleeve between the drying agent and the metal.

 

[Brent]

We always put a sacrifice anode of zinc on our boat motors to protect the aluminum housing from corrosion. The weaker metal (zinc) would corrode first saving the aluminum housing. Not sure if that would help in this case.

 

[Keyman62421]

If YOU think there is a possibility of contamination getting in your gun, throw that filter away!

Buy a new in line filter. 

 

[Bigragu]

There is a divider plate within that cylinder that sits either on top of the cotton media or below it(can’t remember but I’ll find it in my lightning break down pics.) that’s the dissimilar metal. I believe it is stainless.

I showed this same contamination in my rebuild thread from three years ago. You’ll have to source a round cylinder brush and clean it the best you can like I did, and use a shop compressor to blow out any bits and pieces you remove of that gunk. Then do a wipe down with isopropyl alcohol to make sure it’s clean inside.

before you insert the cotton media take a sharpie and write the date down on it(unless you’re good about writing things down in a maintenance log book)

that o ring that’s on the divider plate- do not toss or ruin that o ring as it is not in the repair kit. It can be reused, though

 

[Bigragu]

Don’t forget to switch out the dessicant media within the aluminum block that your fill whip is attached to, and replace the spring in the check valve that’s a part of that block 

my thread also had the type of dessicant media that Hatsan told me to use, which is the same type that was used when the lightning was built at the factory.

 

[GBGUNNER]

Form this side of the computer screen I feel there are deposits being placed in the filter. the majority seems to be in the bottom where the water absorbed is settling between uses. There are microscopic chemicals and dirt in our humidified air. Depends on where you live, humidity, catalytic converter emissions, agriculture spays. Might even be mold.