Properly Refinishing Steel Tanks?

[Luis H]

It is kind of weird to read this stuff. Of course, ZRC is the cheapest way to go and is the most practical in a kind of logic applicable to third world countries. However, decades ago, we used to galvanize military surplus tanks at various places (like San Diego Sandblasting). The zinc coating was applied by "metalizing", a kind of plasma jet which applied zinc metal to steel. The result was good for about 5-10 years of heavy use. They would probably last forever if touched up with "zinc rich" which we had never heard of back then. During metalizing, the surface of the steel is heated slightly but not enough to hurt anything. Prior to applying the zinc, the tank was sand blasted. I was told that not even a finger print on the tank was acceptable. I still have some old tanks around with these zinc coatings.I don't know what happened to this practice. Thirty years ago, it cost 10 bucks per tank. SDS told me they did not make any money on it but did it as a kind of 'favor" for divers. I believe it.

That plating process is probably now popular in some third world country where they have no OSHA or environmental regulations. I am kind of kidding, but it is the reality for many processes, specially plating processes.

Many of the chemicals used in many plating processes has either being banned or the cost of handling and disposing them makes them impractical or not cost effective to deal with.

There are plenty of plating shops that have gone out of business because of antiquated facilities or processes that can not meet new safety and environmental standards. Many of the chemicals used during the plating process or to produce the plating chemicals are very nasty.

They are just not allowed to dump all their used nasty chemicals on the back stream or into the ground anymore…

 

[pescador775]

Yeah, Chromalot is out of business. However, metallizing (flame spraying) is different. Possibly, the demand for the process is weak and does not justify broad use of the equipment. I got a cost estimate to metallize some tanks at a shop in my area (VA Beach) and they quoted over $100/tank. My understanding is that this shop had never sprayed a SCUBA tank. There probably isn't much demand from divers for this process anymore.

 

[MSDT Mark]

Conclusion, I used a 95% Zink spray product to cover these cylinders at the beginning of dive season. My first thoughts were this is not a durable option. However, these cylinders have well over 100 dives and look great. I will Zink coat the bottom of the cylinder again because this is an obvious wear area. With that being said no rust, anywhere.

I did talk with Mark an instructor at PSI about the use of epoxy or POR on the exterior. I was told as long as the cylinder integrity is good and no rust, go for it. With that being said epoxy is porous and should be covered with a clear coat as PerroneFord suggested early in this thread.

The Zink option has proven to be a very durable choice in protecting the cylinders from oxidation. The only thing I’ll do different next time is use ZRC. I’m convinced that ZRC will be bullet proof…

Mark