a question about salt pots

[Matt Bower]

I've been reading up on high temp salt pots, and I have some questions for folks with relevant experience.

 

1) Does the extra longevity of 316 stainless for the pot justify the extra cost? Is it true that 304 doesn't last much longer than black steel pipes?

2) What is it that causes SS high temp salt pots to degrade? Scaling away from the outside, corrosion from the inside, or both?

3) Has anyone here ever considered a ceramic pot? I suspect that the right ceramic tube would be more or less impervious to both oxidation and chemical attack. From what I can tell, industry often uses ceramics for this application. Even if I'm right, I'm not sure what the right ceramic would be. But I know where to get slip-cast, close-ended alumina and mullite tubes greater than 3" inside diameter. The cost is something like twice that of comparable SS, but they might make up for it in longevity. I'm just not sure. (The same place sells some more exotic ceramic tubes, including zirconia, but they're even more expensive.)

4) Anybody ever tried ceramic coatings like the various ITC products to improve the longevity of their SS pots?

[kb0fhp]

The recommendations are use of inconel for high temperature dalt pots. Many of the large ones that I have used - and I am talking 20 feet long or so (and they were used for aluminum and contained ntrate salts) used firebrick.

 

I would suggest that you give a call to AJAX - they make salt pots.

 

Scott

[Howard Clark]

Scott the smallest commercial rig is too big to be practical in the small one horse forge shop.

 

316 does last longer than 304. In my experience 304 is not much better than black pipe for high temp salt applications. The corrosion is primarily due to the flame atmosphere impinging on the outside of the pipe, and not the salt inside it.

 

I think the problem with ceramics might be expansion/contraction issues. Never tried it though, so I do not know for sure.

 

I like simple, and shop repairable. I think many make things too complicated.

[kb0fhp]

I was looking to ask them what they thought regarding liners - not that you get one. I have some data buried away at my desk - I will try to retrieve it when I get back from vacation

[Matt Bower]

Thanks, Scott. I may give them a call. Haven't been able to find any good discussions on the web of what industry uses for pots or pot linings.

 

Howard, thanks. If oxidation from the heat source is the problem, some of the ITC products that are designed to protect steel from oxidation in high temp environments may help.

Edited December 27, 2007 by Matt Bower