Repairing exterior rust on steel tanks

[captain]

850F is not hot enough to affect the chrome molybdenum steel used in dive tanks. It strength comes from the alloy itself not heat treatment as in the case of aluminum tanks.

 

[lowviz]

...//... there is no way you would take a used tank and have it re dipped as it would no doubt change the metallurgical composition of the cylinder to an extent that could only be defined by taking test samples and confirming the strength on the material in theory.

I have enough 72's that I could afford that test. Hydrochloric acid (Muriatic acid) will disappear zinc in an instant. Cleaning is easy. Then the tank gets pickled (acid again) and zinc dipped. I need to look into the cost of hot-dipping a tank.

850F is not hot enough to affect the chrome molybdenum steel used in dive tanks. ...//...

This has always been my suspicion. But when you ask, everybody errs on the side of lawyers and the answer is invariably "NO". Well worth the cost of a hydro to find out...

 

[Diving Dubai]

850F is not hot enough to affect the chrome molybdenum steel used in dive tanks. It strength comes from the alloy itself not heat treatment as in the case of aluminum tanks.

What a load of crap! Sorry to be so blunt. All metrallics get heat treatment. I should kinda know given I spent 10 years as a materials scientist in aerospace.

The treatments alter the properties of the material to suit your final component. Hardening and tempering as a simpe example

That said, tests have been carried out on black rolled high tensile steel as used on car parts and I beams which show a deviation post HDG of only 0.4% of the tensile strength which is good.

Still the process is at +400C, and there is a risk of embrittlement. A manufacturer will closely control their process, and have test coupons to ensure everything is within parameters, which will include no contaminants in the molten zinc baths which could affect the steel. Your local galvanising shop - probably not.

@lowviz hydro' tell you very little other than the tank can hold a pressure and expand and contract within limits.

However what do I know?

Faber have rejected HDG

 

[StefinSB]

What a load of crap! Sorry to be so blunt. All metrallics get heat treatment. I should kinda know given I spent 10 years as a materials scientist in aerospace.

The treatments alter the properties of the material to suit your final component. Hardening and tempering as a simpe example

That said, tests have been carried out on black rolled high tensile steel as used on car parts and I beams which show a deviation post HDG of only 0.4% of the tensile strength which is good.

Still the process is at +400C, and there is a risk of embrittlement. A manufacturer will closely control their process, and have test coupons to ensure everything is within parameters, which will include no contaminants in the molten zinc baths which could affect the steel. Your local galvanising shop - probably not.

@lowviz hydro' tell you very little other than the tank can hold a pressure and e land and contract within limits.

However what do I know?

Faber have rejected HDG

The Faber Statement you posted has no verifiable references and sound more like marketing FUD than anything else.

 

[Diving Dubai]

The Faber Statement you posted has no verifiable references and sound more like marketing FUD than anything else.

Fine, who am I to tell you what to do. As someone with more knowlege of materials than most on here, I wouldn't ever re hot dip gal a tank. You clearly know better, so go right ahead and fill your boots.

While you're at it, stamp a + on the tank so you can overfill, as everyone knows that working pressures are a guide and tanks can take much more.

 

[captain]

Double post.

 

[captain]

What a load of crap! Sorry to be so blunt. All metrallics get heat treatment. I should kinda know given I spent 10 years as a materials scientist in aerospace.

The treatments alter the properties of the material to suit your final component. Hardening and tempering as a simpe example

That said, tests have been carried out on black rolled high tensile steel as used on car parts and I beams which show a deviation post HDG of only 0.4% of the tensile strength which is good.

Still the process is at +400C, and there is a risk of embrittlement. A manufacturer will closely control their process, and have test coupons to ensure everything is within parameters, which will include no contaminants in the molten zinc baths which could affect the steel. Your local galvanising shop - probably not.

@lowviz hydro' tell you very little other than the tank can hold a pressure and expand and contract within limits.

However what do I know?

Faber have rejected HDG

Galvanising - Affect on Steel Strength

Faber's decision not to use HDP is most likely environmental regulation and cost. Part of the reason PST went out of business., HDP sites are becoming fewer and fewer because of environmental regulation. There were several here locally and most are gone.

 

[lowviz]

...//.. @lowviz hydro' tell you very little other than the tank can hold a pressure and expand and contract within limits.

That's good enough for me.

 

[Eric Sedletzky]

I did not advocate Ospho in place of blasting, I advocate it as a treatment after blasting but if blasting is not an option it is better than nothing.

Agreed.

 

[rjack321]

I know that if you have the inside of a tank shot blasted it automatically needs a hydro.

Interior shot blasting does not require a new hydro. Although the only people really capable of doing it right with the correct media which doesn't remove any metal (just the corrosion) is a hydro shop. Mine has blasted the epoxy liner out of a couple of lp72s for me, way easier than burning out my tumbler with days of rolling.