Surface Corrosion on AL tank??

[al248005]

I just picked this tank up for $15. It has a current viz good through this time next year and the hydro still has 2 yrs left. Not being fimiliar with how the actual process goes for viz inspection do you think this would pass another years inspection when it comes up for next time? Heres some pics of the corrosion taking place. Is there anything that can be done to help slow down the amount of corrosion taking place??

 

[fire_diver]

From the pics, it doesn't look too bad. A qualified inspector would have to make the determination though. Corrosion or scratches can't be over a certian depth without possibly compromising wall integrity at pressure.

 

[Colliam7]

Not being fimiliar with how the actual process goes for viz inspection do you think this would pass another years inspection when it comes up for next time? ... Is there anything that can be done to help slow down the amount of corrosion taking place??

As fire diver said, it is hard to tell from the pictures how 'advanced' the corrosion is, but it does not look too bad. It looks like simple surface oxidation, which may reflect the condition in which it was stored before you bought it. When I inspect a tank, I look for the depth of the pitting associated with the corrosion, both INSIDE and OUTSIDE, so it is hard to say from afar if it would or would not pass. One thing you can / should do is rinse your tanks after each dive, particularly ocean dives. I am curious about the appearance of the tank, although it could just be the lighting in the picture. It almost looks like it was once painted, and the paint removed and the tank wired brushed / polished, but that could be my imagination. When was the very first hydro (i.e. how old is the tank)?

 

[spectrum]

I picked up a few painted Al80s some years ago that looked like crap. After removing the paint there was similar deterioration, probably worse underneath. Sakt water was gettin trapped under the broken paint. They have gone unquestioned through a number of vis and a hydro cycle.

What will matter is how your inspector interprets things. If you get grief get a second opinion.

Pete

 

[al248005]

No they were not painted and then the paint removed. It was just the way the light was hitting them. It was really tough to get good pictures of them. I ended up taking the pics in complete darkness. The original hydro was done in '94 so yes it does have some age to it but for a tank that old I really didn't think it looked all that bad. I did check to see if it was made of the bad alloy before I bought it and it is not. Its a Catalina tank. By the way thanks for all the replies. I am new to buying tanks and this info is very helpful.

 

[airstream]

I have two of the same cylinders, right now as we speak I am using a non-caustic stripper to remove the clear coat....mine actually look worse than yours here is a link to Catalinas' stripping info...I'll let you know how it goes!

from Catalina Cylinders under tech support:

"Technical Support Document

Paint Removal from Aluminum Cylinders

February 10, 1996

Catalina Cylinders recommends that paint be removed from aluminum cylinders by the use of gel-type (non-caustic) paint strippers instead of sanding, abrasive blasting, or any methods of exposure to heat. Removal of paint from a cylinder by sanding or abrasive blasting can also remove metal thus reducing the wall thickness of the cylinder and reducing the integrity of the cylinder.

Catalina Cylinders has found that gel-type (non-caustic) strippers work well in removing old paint and do not remove metal from the cylinder when properly used. Gel-type (non-caustic) paint strippers are commonly found at your local hardware or paint stores.

Do not use caustic strippers to remove paint from aluminum cylinders. Make sure the gel-type paint stripper selected is compatible with aluminum.

Always replace the cylinder warning label after refinishing a cylinder. Replacement cylinder warning labels are available from Catalina Cylinders Customer Service Department upon request."

 

[WetBoy101]

You can clean the outside of the tank with an aluminum cleaner from NAPA. I use it on my fuel tanks. Spray on and rinse off. It will make the tanks look a lot better and make it easier to examine the scratches that dont clean off!

 

[bigrich954rr]

has any one tried waxing the tanks? like auto car wax ?

i use to work with alum alot in salt water and regular water it was bare alum or Anodized aluminum for colors. We use to wipe the parts down with auto wax to keep them looking nice longer it wears off and its not a end all but helps. water doesnt get trapped under the wax as it just bonds then wears off

started do this cause one of the coating used on the alum we installed trapped water under the coating and would peel and flake off after time costing a bunch of money.

 

[WetBoy101]

I think waxing them would make them slip out of the bands!?

 

[Kiwi303]

I think waxing them would make them slip out of the bands!?

Use surfboard wax! that stuff is sticky