The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Tanker used for nitric acid(98%)

2007

1. Introducing myself
I am a research engineer in a company. I got my PhD degree with the major material science and engineering.

At present, I notice that in China, most of the tankers for nitric acid(98%)is made of pure Aluminium which has good corrosion resistance, but I know the pure Al has no enough strength.so there is crack and leakage cases sometime. so I want to know how is the condition in North American and Europe? you know, in these countries, Al is widely used in tankers, coal cars...,so what kind of Al alloy they use for nitric acid? and how is the tanker's life span?...
Please provide me some information on that. many thanks.

Liu FangFang
corrosion and corrosion control - Beijing, China

---

2007

The book, Materials Selection for the Chemical Process Industries, 2nd Edn., ISBN 1-57698-025-1, has a chapter on nitric acid.
Only a few aluminum alloys are commonly used: 1100, 3003, 5052 & 5454. The first 2 can be welded with 1060 filler;* the latter 2 with 5356 filler. *1100 filler is sometimes used, but risks intergranular attack if the Fe content is too high, so the purer 1060 is preferable.

304L stainless (UNS S30403) is frequently used. A nitric acid grade (NAG) with extremely low C, Si, P and S limits gives improved corrosion resistance, especially for the welded condition, but is likely more expensive. And, the stainless steel is 3x as heavy as the Al alloys. With proper engineering and high quality welding, aluminum alloys may be more cost effective. See also 'Stainless Steels and Nickel-bearing Alloys in Nitric Acid' available from the Nickel Institute:
http://www.nickelinstitute.org/index.cfm/ci_id/10626/la_id/1.htm

Are you able to examine the cracked & leaking tank cars? It would be helpful to know the alloy, welding alloy and whether failure was from intergranular corrosion, general corrosion, weld corrosion, weld cracking, fatigue or multiple types. Some newer 5000-series Al alloys have lower limits on Fe, Cu, etc. and also lower Mg (which can segregate in grain boundaries) so less subject to corrosion than 5052 or 5454.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.