HCL Corrosion | Materials And Corrosion Control

·         Damage is most often associated with dew point corrosion where vapors containing water and hydrogen chloride condense.
The first water droplets that condense can be highly acidic (low pH) and promote accelerated attack.

·         Dry HCl is normally not corrosive.

·         The critical factors are HCl acid concentration, temperature and alloy composition. The severity of corrosion increases with increasing HCl concentration, temperature and oxidizing agents (oxygen, ferric and cupric ions).

·         Chlorides may be stripped from the catalyst and react to form HCl that carries through the effluent trains, regeneration system (stagnant and relief valve piping) as well as the recycle, net gas and fuel gas systems.

·         Serious corrosion can also be found at mix points where dry chloride containing vapors mix with streams containing free water or where water saturated streams are cooled below the dew point.

·         Minimize carryover of water and chloride salts from upstream units including neutralizing amine hydrochloride salts.

·         Maintain regenerated catalyst chloride between 0.9 to 1 wt% and moisture level 15 to 25 ppmv to minimize corrosion in the net gas, recontact and AET sections.

·         Selective use of corrosion resistant nickel base alloys.

·         Chloride levels in the Platformer unit gas stream and the AET unit inlet and outlet gas streams

·         Corrosion Rates

·         Metals Handbook, “Corrosion,” Volume 13, ASM International