Study on the Corrosion Behavior and Inhibitor Protection in Reclaimed Water Pipelines of Steel Enterprises

Abstract

For the corrosion problem within the reclaimed water transport pipelines of a steel company in Hunan, water samples from typical reclaimed water sources were collected for water quality analysis. The corrosion behavior of the reclaimed water transport pipelines was systematically investigated through hanging plate tests, microbial culture counting, electrochemical testing, scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and X-ray diffraction(XRD). Moreover, the corrosion inhibitory effects of hydroxyethylidene diphosphonic acid(HEDP), 2-Phosphonobutane-1,2,4-Tricarboxylic Acid(PBTCA) and polyaspartic acid(PASP) were examined. Results showed that the quality of reclaimed water was significantly impacted by biological dephenolization wastewater, blast furnace drainage, total drainage in the direction of five meters and drainage from three water stations. The passivation film on the surface of reclaimed water pipelines was destroyed by the action of Cl- and SO42- in the water, while iron bacteria and sulfate-reducing bacteria promoted corrosion, resulting in the formation of Fe(OH)3 and FeS. After the addition of HEDP and PBTCA corrosion inhibitors, a decrease in the thickness of the corrosion layer was observed, and the corrosion rate fell below the national standard. Following the addition of PASP, the corrosion products on the surface of the hanging plate were loose and porous siderite. In the low-frequency impedance region, Warburg impedance characteristics were displayed, and the corrosion inhibition rate was only 3.9%.

Keywords

• carbon steel; corrosion inhibitor; reclaimed water system; corrosion rate