PDA

View Full Version : hot dipping



MxDiver
12-28-2008, 21:43
I got another set of (free) used steel tanks which need to be refinished.
Last time I did this I had them tested before refinishing and ended up using cold galvaninzing compound, this was not as lasting as I had hoped.
This time I want to hot dip the tanks and then having the visual and hidro done. Anything I should worry about?
Regards

ektess1
12-28-2008, 21:53
If they are free, get them hydo and viz.
Only if required.
Dive them untile they fail. They are free.
Wish I got free tanks.

PS: They should not need any kind of recoating.

cummings66
12-29-2008, 18:43
Did you use the ZRC stuff? The other isn't as good. Use ZRC and roll it on. My cylinders are still going strong with no problems. Hot dip galvanize a steel cylinder and it will most likely not be a scuba cylinder any longer. From what I understand of that process it's pretty hot, and even though steel can go to higher temperatures than al, the process is risky. Yes, they do it new and hydro it afterwards, but the process is designed for scuba cylinders.

Be very careful here, contact the manufacturer and ask them how to get it done and do it as they say.

PS, many older steel cylinders that are painted and look rough are galvanized under the paint, remove it and you're done.

If I recall right, you used a steel wire brush on the cylinder you refinished. If so, that's bad as it can embed small particles in the cylinder which will rust. If you used ZRC and a wire brush that's why it failed. If not, I don't know. A good process works as I and numerous others have used ZRC with no problems.

So, what brand cold galvanizing paint did you use?

jbres1
12-29-2008, 21:16
How did the finish look after it was rolled on ?

I sprayed my tanks with ZRC. They look great, but there was so much paint dust on the floor I think I wasted alot.

Rolliing on may be a better way to go.

Jim Breslin

captain
12-30-2008, 10:14
Use ZRC Galvilite, clean the tank to bare metal, roll on 3 coats with a foam roller. The spray can is a waste of time and money.

MxDiver
12-30-2008, 22:39
Did you use the ZRC stuff?
I did not use ZRC, I was not able to find it locally.

The other isn't as good. Use ZRC and roll it on. My cylinders are still going strong with no problems. Hot dip galvanize a steel cylinder and it will most likely not be a scuba cylinder any longer. From what I understand of that process it's pretty hot, and even though steel can go to higher temperatures than al, the process is risky. Yes, they do it new and hydro it afterwards, but the process is designed for scuba cylinders.

Be very careful here, contact the manufacturer and ask them how to get it done and do it as they say.

PS, many older steel cylinders that are painted and look rough are galvanized under the paint, remove it and you're done.
The cilinders were made by scuba pro, they are steel 72s, how can I tell if they are galvanized?

If I recall right, you used a steel wire brush on the cylinder you refinished. If so, that's bad as it can embed small particles in the cylinder which will rust. If you used ZRC and a wire brush that's why it failed. If not, I don't know. A good process works as I and numerous others have used ZRC with no problems.

So, what brand cold galvanizing paint did you use?

I used rustoleum cold galvanizing compound (rattle can), the problem I have is the adhesion, everytime anything hits the tank it just peels the spray coating, I don't use the tanks much as they are currently set up as doubles, but I am tired of having to touch them up, so I was looking for a more resistant finish.

mitsuguy
12-31-2008, 09:11
This has probably been said/asked before, but would there be anything detrimental to painting a steel tank like you would paint a car? There is no heat involved in a basic 2 stage paint and it would protect against rusting externally...

captain
12-31-2008, 09:53
This has probably been said/asked before, but would there be anything detrimental to painting a steel tank like you would paint a car? There is no heat involved in a basic 2 stage paint and it would protect against rusting externally...

Listen to what is being said. ZRC is 90% pure zinc, molten zinc is what the tank is hot dipped in. If you can't find it locally you can buy direct from ZRC.
If you don't see any rust on the tank where the paint is chipped off it is more than likely galvanized under the paint.

cummings66
12-31-2008, 18:25
I used rustoleum cold galvanizing compound (rattle can), the problem I have is the adhesion, everytime anything hits the tank it just peels the spray coating, I don't use the tanks much as they are currently set up as doubles, but I am tired of having to touch them up, so I was looking for a more resistant finish.

OK, I got you. Do yourself a favor, strip the so called paint you have on it off and mail order ZRC. It is the only way to go IMO. It's very good paint and looks like a normal galvanized cylinder when you're done rolling it on. It really does work well. I like Captain used three coats, be careful on top where the hydro numbers are, you can't obscure them or the cylinder will fail a VIS and even a hydro if they can't find it. Getting rid of a number is grounds to condemn a cylinder, even if it's buried in the paint. An inspector has no way to know there's numbers under there.

ZRC Galvanite is the best there is, finish the steel surface and roll it on, it will not flake off nor come off with scraps and dings. It's on for good. Trust me, I've scraped mine on rocks and it's still good.

It is very expensive though, but a little rolled on goes a very long ways so in the end it's not bad per cylinder. Prep the steel per the standards they require and it'll be good.

How to tell if a cylinder is galvanzied, well, aside from the color look for rust. A plain steel cylinder if it's bare will rust before your eyes, which is why it's a PITA to strip and paint it, it wants to rust before you get the paint on, it's a very fast process. That's why you read lots of stories about flash rust on O2 cleaning. Get it wet and here comes the rust, be in a humid environment and it'll rust right before your eyes. No rust and if it was wet means it's probably galvanized.

ZRC, accept no substitute, and don't spray it on. Too expensive to do, plus they even suggest rolling it on. You get a thicker more durable coating that way. I buy it directly from the manufacturer, it's the cheapest place I've found to get it. Nobody locally has it, or even heard of it. For the other person, yes you can paint it with paint if you so choose, but be careful to not obscure the details and absolutely do not bake it. Never a good idea. I've got a buddy who painted his steel cylinders in one of those glow in the dark green colors, auto paint. Looks very good, except for the glow it looks factory.

captain
01-01-2009, 12:26
ZRC makes several products, this is the one you need,

ZRC - ZRC Galvilite Galvanizing Repair Compound (http://www.zrcworldwide.com/p_galvilite.asp)

MxDiver
01-06-2009, 23:31
All right, I will see about getting the ZRC compound to do both the tanks I just got and redo the other ones. Thanks guys