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Corrosiveness, Rusting of Pre-Hardened P-20 Steel

Hello,
This is my first questing on this website, please excuse my netiquette. We have a pneumatic pressure vessel made of 17-4PH, H1150 Stainless Steel that has been serving us for almost 8 years, and is working pretty well. We need to make a similar one and the quotes I have received are pretty high, mostly due to the high cost of this particular stainless steel. Hence I am looking to get this remade with P-20 Steel. The cost is low, but I don't know how good it would be 5 years down the road.

Does anyone have an idea of how fast P-20 steel corrodes or rusts or degrades in normal working conditions. This part will not get in contact with any corrosive agents, not even water. I am trying to compare P-20 Steel and 17-4PH Stainless Steel. I could obtain mechanical properties on the web, but not durability. If the steel corrodes or rusts or degrades, what kind of a finish should I examine to keep its life for about 5 years.

Can anyone comment on this material.

Thanks,

Shankar Tadavarthi
- Mishawaka, Indiana, USA
2006

P-20 exposed to the humidity of the athmosphere rusts in hours and gets pits in days. If you could keep it covered all the time with heavy oil or preferably, grease, it can last months w/o signs of tarnish or rust. The problem, and I think the former manufacturer saw it, is that this may not be possible or practical and the risk of some of this protection be lost is high. You may want to explore a plating such as electroless nickel.

Guillermo Marrufo
Monterrey, NL, Mexico
2006