Elucidating the corrosion characteristics of brine heater and evaporator condenser alloys during acid cleaning of MSF plants and its mitigation

Inorganic scaling is a serious operational challenge in MSF technology which is managed through acid cleaning. The corrosion of MSF tubing materials during acid cleaning is a serious threat to the integrity of MSF evaporators, therefore the use of suitable corrosion inhibitors is a necessity. In the present work, a new corrosion inhibitor, poly(N1,N1-diallyl-N6,N6,N6-tripropylhexane-1,6-diaminium chloride) (PDTDC) is proposed and assessed in terms of performance in typical acid-cleaning conditions. The corrosion of CuNi30 and CuNi10 alloys and their protection mechanisms have been studied using weight loss, electrochemical, and surface analysis techniques. The results reveal that alloys corroded actively but also showed some degree of passivation. The CuNi30 exhibits higher corrosion resistance than CuNi10. PDTDC reasonably inhibited the alloys' corrosion and remained stable for 72 h. The addition of 100 mg/L PDTDC to the corrodent reduces the corrosion rate of CuNi30 and CuNi10 from 1.60 ± 0.08 mm/y and 18.96 ± 0.95 mm/y to 0.37 ± 0.02 mm/y and 8.85 ± 0.44 mm/y resulting in surface protection of 77 % and 53 %, respectively after 72 h at 30 °C under static conditions. Inhibition efficiency of 73 % and 79 % is afforded by PDTDC (100 mg/L) for CuNi10 and CuNi30, respectively after 72 h immersion at 40 °C under hydrodynamic conditions. PDTDC is a highly promising starting material for inhibitor formulation for acid-cleaning applications.