HF acid corrosion
HF acid corrosion
(OP)
I am a mechanical engineer in the industrial valve industry and deal a lot with valves in HF acid service. Is there any kind of treatment that can be done to steel to improve corrosion resistance? I know that annealing B7 studs improves corrosion resistance but have not heard of anything being done on valve bodies.





RE: HF acid corrosion
with HF you need to be more specific as to the service conditions. in operating process units the conditions are pretty severe and materials selection is the big issue as opposed to heat treating lesser grade materials.
RE: HF acid corrosion
I just recently had a customer reaquest a valve in solid monel because acid is eating the steel one (steel is common in most places of the alky unit for valve body material they just have monel trim) The particular valve size is not currently availible anywhere and I am trying to find out if I can make the steel one last longer.
RE: HF acid corrosion
short of going to a higher grade of materials about all you can do is limit the velocities in the body by proper sizing, and attempt to control the cavitation with limits on valve d/p.
RE: HF acid corrosion
This is more cost effective than supplying a complete valve in Ni alloy etc. However, the ability apply the weld overlay depaends on the type of valve and the design.
RE: HF acid corrosion
RE: HF acid corrosion
I don't believe there is any heat treatment or simple surface treatment that you can apply to WCB which will improve its corrosion reistance in HF service. Hence my original posting referring to overlay.
RE: HF acid corrosion
RE: HF acid corrosion
RE: HF acid corrosion
Our experience from laboratory corrosion testing and piping components from HF alkylation units around the world showed very definitively with wrought carbon steel, at least, that keeping the cumulative level of residual elements (copper + nickel + chromium) to less than 0.20 wt. % was beneficial to minimizing corrosion of carbon steel in HF acid service. The concept was published by NACE in 1993 (Paper 623). Note the permissible level of these same elements per ASTM A216 is 1.0% max. Of course, in general, carbon steel should not be used beyond its generally accepted limit in anhydrous HF, namely metal temperature below 150F. Fluid velocity also is an important factor in the corrosion rate.
To answer your specific question ... other than what has previously been offered in this forum (monel weld overlay, for instance) I know of no treatment to significantly improve the corrosion resistance of carbon steel castings to anhydrous HF acid.
RE: HF acid corrosion
marciogerep
RE: HF acid corrosion