Tank condition questions

[mooch4289]

Two questions for those of you with experience VIPing tanks. First, I've got an AL80 (Catalina, from 1989 and not the 6351 alloy) that I got from an acquaintance about 5 years ago. It was painted black. Last year I got the tank hydro'd/VIP'd but the visual is now out of date. I didn't like the old scratched up paint, and as I'm going to be doing alot of saltwater diving soon, I'd prefer a plain metal tank. I got some aluminum compatible paint stripper, got the tank all stripped, and I noticed a few marks in the tank. First, about halfway up the side of the tank, there's a ding/gouge about an inch long, probably close to 1-2mm deep. Also, there's a round 1/4" dent on the bottom corner (where side meets bottom) of the tank - looks like it hit ground or a rock a little hard at one point. As I've barely used the tanks in the last year, it's obvious to me that the tanks were damaged THEN painted over. Damaged, it subsequently passed both hydro and VIP with these painted over, but now without that paint, I'm concerned they may not pass inspection. Is it even worth getting it inspected, or should I save my money for a new tank.

I also got a used AL63 for my fiance (hydro'd 2007, manufactured in '92). It's got a seemingly plain metal finish, but a plastic coating on the tank that's since been cracking and falling off, and at the cracks it's been corroding. Due to the corrosion, that tank also got stripped and cleaned and looks great now, but I was just wondering, is it common to put clear plastic coat finishes on aluminum tanks? It seems kinda counter productive and was obviously not doing a very good job at protecting the tank. Thanks for any comments

 

[Skooter]

According to CGA 6.1 the first tank may be a gonner according to your description. Basically for a scratch or gouge on the sidewall of the tank there are two ways to look at it. If the sidewall thickness is unknown you are allowed 1/32" (.787 mm). If the sidewall tickness is known the scratch can be 15% of the designed wall thickness. Do some homework and find your tanks design specs and take it with you o have them tested. Talk to the test facility about it at that time.
As far as dents go if they don't reduce the wall thickness they are generally ok up to 1/16" deep and not larger than 2" in diameter. Anything other than that will probably be condemned.
The clear coat on the other tank is just that. Considering the age it would be expected to be cracking and peeling. You did the best thing by removing it. Problem solved and should not cause anymore problems.

 

[mooch4289]

Thats kinda what I thought. I was surprised it would've passed hydro/inspection with the damages, but then again, condemning a tank is and should be based on conservative estimates. I'd try to put a picture on here but can't find my camera. Thanks

 

[spectrum]

When you say 1-2 mm is that actual depth or are you counting raised metal surrounding the blemish?

I had some painted ugly ducklings that I stripped a few years ago. There were a few similar bus smaller gouges, I dressed the high points off with a flat file and they didn't look nearly as bad and VIP'd just fine.

This AL walls are on the order of 1/2 inch thick so there is some thickness there to work from.

Pete

 

[superstar]

The tank passed hydro with the gouge so it should not be an issue. If you don't like the visual results go to a different dive shop for the vip.

 

[mooch4289]

Spectrum, I'm glad you brought that up. It looks to be about 1.5-2mm, but that's from the raised metal surrounding it. From the undamaged section next to it, it's really not that deep (.5 or less). I might have to try carefullly filing the high point down a little to smooth it all out.

 

[Skooter]

The tank passed hydro with the gouge so it should not be an issue. If you don't like the visual results go to a different dive shop for the vip.

FYI the information I gave above is what a hydro test facility is required to go by.

Spectrum is 100% correct that you can remove the raised area of the scratch then measure. Just be careful to not remove any of the tanks sidewall just the raised metal. I would suggest taking it to your local test facility and talking with them about it before doing anything to the tank. Have them look at it and file the raised area while you watch, measure the gouge and see where it is at. That way you won't have a retester just condemn it becouse he see's file marks on it, and the retester will feel a lot more comfortable with the conclusion if he is the one running the file. I have done this numerous times for people at no charge. If the gouge is ok then have it tested, if it is to deep thank them and save the cost of hydro.