Tom Eagar's hot dog cooker stress corrosion cracking

Brief reference. The cooker was supposed to be 316 (Mo-bearing, pitting-resistant) but was built with 304, which corroded in chloride service.

You can add some molybdenum. Two percent molybdenum makes 316, four percent makes 317. Often used for in-the-body applications where you have high chloride concentrations. 316 is fairly common — that's what they were supposed to use in my hot dog cooker. They didn't, they used 304, and it just corroded. So this is for pitting resistance, mostly in chlorides.

Single-sentence aside while showing transgranular SCC in a 308L weld photomicrograph. Tom links the heat-exchanger image to his own hot dog cooker, which failed by SCC in the base material.

I'll show you what a cracked material might look like — a little bit scary. This actually is caustic cracking, but it's transgranular stress corrosion cracking. That's quite a bit of cracking in that 308L weld metal. This is carbon steel shell, 308 weld metal, but 316L tube sheet in some heat exchanger, and they had some caustic sodium hydroxide solution, and these things just crack. That's basically what happened to my stuff — my hot dog cooker — it was basically stress corrosion cracking, although that was in the base material.

Single-line reference to "our hot dog cooker" — 304 stainless failed within days at high chloride concentrations from hot-dog brine. Used to anchor the chloride-vs-time SCC plot.

Here's another thing — effect of chloride concentration on susceptibility of type 304. Test time in hours versus the crack specimen cumulative. As you march up from 10 parts per million chloride — if you condense the air in Cambridge, Massachusetts, because I've done it, and measure the chloride, it's 5 ppm chloride. The drinking water, which is pretty good in this area except in the winter when they're putting salt on the roads, is around 10 or 20 parts per million chloride. 100 parts per million chloride, you're getting to the EPA drinking water level. 1500 parts per million chloride, we're getting into the brackish water area. Sea water is like 30,000. You can see test time — this is a log scale — your stainless steel — this is actually our hot dog cooker, in a sense. Lots of chlorides in that, and those dogs and 304 just couldn't cut it at the high chlorides, and failed within days.