Feed requirements using 35% HC1 are approximately 2 times those of H₂S0₄. In addition, it is generally more expensive and more hazardous to handle than H₂S0₄. One of the major drawbacks of HC1 is that it adds highly corrosive chloride Ions to the water which can penetrate passive oxide films on metal surfaces, setting up local anodic cells. High chloride concentrations can also be extremely corrosive to stainless steels.