Corrosion Control of Rusted Carbon Steel in Reverse Osmosis Product Water

The corrosion of rusted carbon steel is very serious in reverse osmosis (RO) product water of seawater. The inhibition effect of sodium hexametaphosphate and zinc sulfate on rusted carbon steel was studied by weight loss method, electrochemical tests and surface analysis techniques. The results indicated that sodium hexametaphosphate and zinc sulfate showed a strong synergistic effect and the optimal ratio of two chemicals was 1∶1. The inhibition efficiency appeared to increase with increasing the inhibitors concentration and the ideal dosage of inhibitors was 20 mg/L when the chemical cost and inhibition efficiency were taken into account. Surface analysis results proved that the combined inhibitors could combine with corrosion product and make the rust layer much more compact.