HCl and 304L Compatibility

304 SS not compatible with HCl. Selection of stainless steels for handling hydrochloric acid (HCl) www.bssa.org.uk/topics.php?article=30 The common stainless steel types, 304 and 316 should be considered non-resistant to hydrochloric acid at any concentration and temperature. Higher grades of stainless steel can have limited resistance, up to around 3% maximum at ambient temperatures, but may suffer local attack, mainly as crevice and pitting corrosion, even at such low concentrations. The steep curves for 316 and the higher alloyed grades on the iso-corrosion diagram illustrate their very limited resistance. Any additional chlorides or chlorine in the acid can be expected to make attack more severe. Nickel based alloys, rather than stainless steels, should be considered for handling hydrochloric acid. Good Luck, Old Salt

Very interesting. We build process skids here where I work, mainly for pharmaceutical use, and on many of them, they have a cleaning stage where they use an HCl rinse followed by a NaOH rinse. EVERYTHING in our plumbing, even valves and instruments, are either 316L or 304L. Apparently the major players in pharmaceuticals don't know ss won't handle HCl. I would think by now the skids made 15 years ago should be showing some effects. Pitting is a major concern in this industry.

More information please concerning the calculations for the following:

I intend to know for welding purpose can i use SS 304L filler material if I have HCl present with a "concentration of 0.5 MOL PPM in vapor phase".

Good Luck, Old Salt

Thanks to all for their reply. But unfortunately my query is related to the filler materials for welding. Yes as far as the storage is concerned, I accept the compatibility specified by all. But could some one clarify with respect to the filling materials.

Contact your welding material supplier and ask them which filler rod you should use, they can probably help more than us here, just kind of guessing?

See #4

Yep, I can verify the weld metal info on this site is god. Some years ago I worked for a FGD fabrication company and we used C-276 frequently. We did welding all the time, and in service I never saw a failure of the weld metal.

In addition to the good information already posted I would caution you highly, and advise a full nitrogen purge of the system and definitely the area of the weld and that your welder have on the proper respirator as welding in the presence of HCL vapors can produce some nasty and highly toxic compounds. (and if I remember correctly flammable depending on concentration)

Thanks to all for their reply.