Effect of nitrite concentration on the corrosion behaviour of carbon steel pipelines in synthetic tap water

This study examines the effect of the continuous decrease of the nitrite concentration on the corrosion properties of a carbon steel pipeline in deaerated synthetic tap water. Passive film, which is composed mainly of maghemite (γ-Fe2O3), was formed in synthetic tap water containing 200 ppm nitrite. A carbon steel pipeline in synthetic tap water containing 100 ppm nitrite was more susceptible to localised corrosion than that containing 50 ppm nitrite due to the effect of the small anode and large cathode area. Uniform corrosion dominates in synthetic tap water containing 50 ppm nitrite.

► Corrosion resistance of the carbon steel pipeline was improved by adding nitrite.
► Passive film was formed in synthetic tap water containing 200 ppm nitrite.
► Localised corrosion dominates in synthetic tap water containing 100 ppm nitrite.
► Uniform corrosion dominates in synthetic tap water containing 50 ppm nitrite.
► To protect the pipelines, the minimum dosage of nitrite inhibitor is 200 ppm.