Hot dip a painted steel tank?

[oxyhacker]

We looked into this a while back, and got estimates of about $65 a tank, for quantities of 12 to 25, plus the cost of making a custom fixture to support the tanks while they were dipped (which must be very firm since the tank is displacing metal not water!). Heat is in the 850 F range, which is acceptable though several sources said the tank should be hydroed afterwards. The heat causes a white ash to form inside the tank, so the tank would also need cleaning, possibly tumbling too.

Adding the that the cost of getting them to and from the galvanizing plant, it didn't seem worth pursuing. If one had a plant willing to handle small orders nearby it would be more practical.

We have seen tanks galvanized like this, but they seemed mostly to belong to people who had a connection at a galvanizing plant, and were able to slip them in.

 

[SDAnderson]

Zinc coating on steel tanks is a subject that has been exhaustively covered on a number of occasions on this board. Most of the information that shows up in these threads is speculation or based upon wrought iron furniture and not worth the electrons consumed.

Use the search function, look for anything written by FredT. There may be others that know as much as he does about the subject but, clearly, Fred is da man. LeadKing is another good source, but the new Worthingtons are "his" tanks and a paranoid mind might be cautious.

Short synopsis of what I've learned from listening to my betters: hot dip galvanizing is the best, but there are viable alternatives. Rinse them well and periodically remove the boots, touch up any dings with ZRC and get on with your life. The cost of blasting or tumbling a tank to clean the external surface usually isn't cost effective and often doesn't produce satisfactory results.

Some relevant reading:
http://www.scubaboard.com/showpost.php?p=151216&postcount=13
http://www.scubaboard.com/showpost.php?p=909800&postcount=18
http://www.zrcworldwide.com/

 

[cool_hardware52]

We looked into this a while back, and got estimates of about $65 a tank, for quantities of 12 to 25, plus the cost of making a custom fixture to support the tanks while they were dipped (which must be very firm since the tank is displacing metal not water!). Heat is in the 850 F range, which is acceptable though several sources said the tank should be hydroed afterwards. The heat causes a white ash to form inside the tank, so the tank would also need cleaning, possibly tumbling too.

Adding the that the cost of getting them to and from the galvanizing plant, it didn't seem worth pursuing. If one had a plant willing to handle small orders nearby it would be more practical.

We have seen tanks galvanized like this, but they seemed mostly to belong to people who had a connection at a galvanizing plant, and were able to slip them in.

My dad had 4 72's hot dipped maybe 35 years ago. Not a big deal as we regularly had fabricated steel items hot dipped. What we did find out was the vinyl or epoxy liner in the tanks burned. Tumbling took the remaining lining right out. 2 of these tanks are still in service.

Lessons learned: 1) Check for a lining that might be damaged, 2) Great way to ease the removal of a vinyl or epoxy liner, 800 degrees F does the trick.

Of course 35 years ago there were maybe 5 times the number of galvanizers in the LA area.....haven't check into hot dip lately.


Tobin

 

[Tamas]

Speaking of painting/coating tanks, what do you guys think of painting the tank with a rust proof paint then coating it in a truck-bed type spary on coating (waterproof) - that should help with future scratches and dings as well as protect from rust on the outside.

 

[mxracer19]

why not just get it powdercoated?

 

[SDAnderson]

Speaking of painting/coating tanks, what do you guys think of painting the tank with a rust proof paint then coating it in a truck-bed type spary on coating (waterproof) - that should help with future scratches and dings as well as protect from rust on the outside.

You'll never pass a visual inspection and might not pass a hydro.

 

[Tamas]

You'll never pass a visual inspection and might not pass a hydro.

because of the rust-paint or the bed-liner?

 

[Tom Winters]

because of the rust-paint or the bed-liner?

Nooooooo - you can't fit a even a small pickup truck in a hydro tank.

 

[Tamas]

Nooooooo - you can't fit a even a small pickup truck in a hydro tank.

huh? gimme me some of what you are smoking.....



....I was actually thinking of only doing the bottom of the tanks, where the boot would be. To protect it from scratches and nicks while on the floor or while loading.

 

[JustinW]

Speaking of painting/coating tanks, what do you guys think of painting the tank with a rust proof paint then coating it in a truck-bed type spary on coating (waterproof) - that should help with future scratches and dings as well as protect from rust on the outside.

I've seen the bedliner stuff, for whatever reason it peels, don't know if it was inadequate surface prep, the galvanizing beneath or if its the salt water, I read a thread on using bed liner material to repair a kayak, and the manufacturer wasn't sure of the effect of prolonged saltwater exposure. This tank I am thinking of gets pretty hard use, several hundred dives on it at least since it was done, probably more.