Corrosion behavior of materials in RO water containing 250–350 ppm chloride

Reverse osmosis (RO) water constitutes about 22% of total desalinated water produced in the world. The rest of the desalinated water is almost entirely from thermal distillation, such as multistage flash (MSF) evaporation and multi-effect desalination (MED) techniques. The RO permeate is more corrosive than water produced by thermal distillation due to its high dissolved salts (TDS) level, particularly chlorides. As the RO water is transported through cementitious or polymer lined pipelines, steel components like pumps, valves and pipes are likely to corrode, if proper material selection is not made. Not much information is available regarding the corrosion behavior of RO water towards the metallic materials particularly steels which forms the bulk of constructional materials. A study has been conducted to investigate the corrosion behavior of some structural materials which include carbon steel 1018, electroless nickel plated carbon steel 1018 ENP, austenitic stainless steel AISI 304, and martensitic stainless steels AISI 410, AISI 420 and AISI 431 in RO water. These materials have been the main constructional materials used in metallic components of pipelines in Saudi Arabia. Studies have been carried out under dynamic conditions (impingement under flow), static conditions (crevice formers) and in presence of an inhibitor (phosphate) using a dynamic test loop. High chromium steels (>15% Cr) appear to provide good resistance where as low chromium steels (<15% Cr) exhibit generally poor resistance under the above mentioned test conditions.