Silicon mastic and Hydrochloric Acid.

[corrosionman]

A Client of mine used a general purpose Silicon mastic
( bathroom mastic) as a gasket sealant for the manhole lid of a conc HCl tank. Does anyone have any experience of the chemical resistance of such mastics. I know that sometimes the acid fumes can be more damaging than the acid itself. The tank is a butyle lined mild steel. The lid did not seat correctly and the fumes + rain water on the lid corrosion damage which took away most of the steel flange and much of the 1" dia stainless steel bolts.
I do not want to worry the Engineer needlessly but maybe another leak will run down the shell and split his tank in two!

 

[Zoobie]

By concentrated HCL do you mean 35%? HCl vapor pressure drops off very dramatically at slightly lower concentrations which really can affect your analysis. Its been a while since I worked with HCl but I did have my share of tank problems. I recall specifically that the vapor pressure effect had a major impact on the vent scrubber sizing to the point where we were evaluating using in-line dilution prior to the tank.

I agree with you about not worrying anyone needlessly but at the plant I worked at a concentrated hydrochloric acid tank rupture was the worst case scenario from a emergency planning point of view such that a catastrophic release would have required an evacuation of all the neighbors in a fairly large radius.

 

[rnd2]

According to Schweitzer's Corrosion Tables:
HCL dilute OK 80 deg. F
HCL 20% OK 80 deg. F
HCL 35% Unsatisactory
HCL 38% Unsatisfactory
HCL 50% Unsatisfactory
HCL Fumes OK 80 deg. F