Cleaning paint off a Al tank

[dave4868]

Done properly, chemically stripping the paint isn't going to damage your cylinder. For what it's worth, painting a tank is a big issue when it comes time for a visual inspection - new paint can hide a lot of different kinds of damage. Removing the paint doesn't raise as many concerns but should still be considered to be an indicator of possible heat damage, either prior to or during the removal process. Any tank with new paint or old paint removed should be referred during the next visual for hydro-testing.

Thanks for the professional perspective.

What about the increased corrosion under some cracked paint on an aluminum tank?

Does an inspector need to scrape open the cracked paint and heavily corroded areas to judge the depth of pitting?

Have you seen it get bad enough to condemn a tank?

In other words, is stripping damaged paint off an aluminum tank worthwhile for other than aesthetic reasons?

Thanks in advance.

Dave C

 

[spectrum]

Cracked paint is bad news, especially for a salt water user.

I picked up a few used AL80s for extras and certain dives where my steels were too negative. These things were painted and ugly. One was factory finished and the second may have had an end user overcoat.

Anyhow after chemically stripping them it was apparent that corrosion was happening under the blistered paint and it was such that no reasonable rinsing would have flushed the corrosive salts out of there. I'm using them now in the "as stripped" mill finish and they are perfectly stable with normal rinsing.

Pete

 

[SDAnderson]

What about the increased corrosion under some cracked paint on an aluminum tank?

A potential problem, to be sure. I'm not certain how much of an actual problem it is, especially if you rinse regularly and do a little preventative scraping.​

Does an inspector need to scrape open the cracked paint and heavily corroded areas to judge the depth of pitting?

S/he certainly should.​

Have you seen it get bad enough to condemn a tank?

I've condemned cylinders for external corrosion. Usually this is associated with tank bands or boots or cosmetic wraps, offhand I can't recall an instance where condemnable external corrosion was located in an exposed area.​

In other words, is stripping damaged paint off an aluminum tank worthwhile for other than aesthetic reasons?

Not in my experience but I'm in the Midwest and though we see salt water tanks we sure don't see as many as some areas. I think removing any loose bits of paint and opening up any soft spots is enough to stop the pitting problem but if you want to take all the paint off, that's not going to hurt - so long as you do the job right. The only consequences are that it will take several days worth of lunch money (and time) to do the work. Personally, I'm not going to fool with it but we can still share the planet if you decide otherwise.​

 

[dave4868]

What about the increased corrosion under some cracked paint on an aluminum tank?

A potential problem, to be sure. I'm not certain how much of an actual problem it is, especially if you rinse regularly and do a little preventative scraping.
​

Does an inspector need to scrape open the cracked paint and heavily corroded areas to judge the depth of pitting?

S/he certainly should.
​

Have you seen it get bad enough to condemn a tank?

I've condemned cylinders for external corrosion. Usually this is associated with tank bands or boots or cosmetic wraps, offhand I can't recall an instance where condemnable external corrosion was located in an exposed area.
​

In other words, is stripping damaged paint off an aluminum tank worthwhile for other than aesthetic reasons?

Not in my experience but I'm in the Midwest and though we see salt water tanks we sure don't see as many as some areas. I think removing any loose bits of paint and opening up any soft spots is enough to stop the pitting problem but if you want to take all the paint off, that's not going to hurt - so long as you do the job right. The only consequences are that it will take several days worth of lunch money (and time) to do the work. Personally, I'm not going to fool with it but we can still share the planet if you decide otherwise.
​

Thanks again! It's great to have your input.

I'm going to take the liberty to draw some conclusions from what you've said and offer a summary regarding the possible need to strip aluminum tanks with cracked and chipped paint, specifically in saltwater use:

• saltwater will be trapped under loose paint despite rinsing (based on increased corrosion under blistered paint and under bands, etc)
• scraping to remove loose paint will help prevent the trapping of salt
• pitting can be severe enough on the external surface of a tank to warrant condemning a tank (probably significantly worse in saltwater use)
• chipping away defective paint can reduce the pitting and possibly avoid having a tank condemned
• removing all the paint will have a significantly positive effect to reduce this problem

Therefore, my previously mentioned method may be worthwhile to some people, since it costs under $15, is easy to perform in less than 40 minutes per tank and doesn't cause damage to the tank.

One's decision will depend on the degree of paint damage, rate of corrosion (frequency of exposure to saltwater) and how much preventative scraping one is required and/or is willing to do as an alternative to stripping.

Pretty much personal preference, all considered, but boy are my tanks low-maintenance and pretty now!

Dave C

 

[n2addict]

Whoa That was great guys. thanks a lot.

 

[Colliam7]

Most of my answers will be similar to Reffraff's.

What about the increased corrosion under some cracked paint on an aluminum tank??

There may be a slight increase in the amount, but I have not seen it to be extensive enough to be a problem for AL tanks (maybe I just need to inspect enough to find that one exception). You have to do a really poor job of rinsing your tanks, and do that consistently, after a lot of dives, for corrosion severe enough to lead to condemnation to develop.

Does an inspector need to scrape open the cracked paint and heavily corroded areas to judge the depth of pitting??

Yes.

Have you seen it get bad enough to condemn a tank??

Not on an AL tank. Corrosion under boots / bands is a problem, but I have seen more issues on steel tanks.

In other words, is stripping damaged paint off an aluminum tank worthwhile for other than aesthetic reasons?

I have not found it to be. As you subsequently mentioned, it is in part a matter of personal preference. But, it does make inspection a bit easier (I don't have to probe and scrape). What causes me more concern is a coat of new paint applied on an 'old tank', particularly when I ask the tank owner about it and get the reply, 'Gee. I dunno. It was like that when I bought it.' In most cases, I immediately wonder, 'What were they trying to cover up?' Stripping, performed properly, is fine. Stripped AL tanks are fully functional, are not more susceptible to the corrosive effects of salt water, and generally look better than tanks that shed paint flakes on the floor (or in your dive buddy's car). If anything, there are fewer worries, because there is no peeling paint for water to be sequestered under.

 

[imasinker]

Ok so here is my reason to strip my tank.... I needed a tank in a hurry, only ones I could get in time to dive was a blue tank. I thought I would strip it down to the aluminum base colour since I now have doubles and I am more apt to use this tank as a deco or stage bottle. God i hate that blue colour, but rentals were all gone and i needed a tank on a long weekend dives.So now you understand why i am thinking about it. LOL....