Corrosion Behavior of Bottom Plates of A potable Water Storage Tank

Abstract

This paper describes the investigation of a corrosion behavior of bottom Plates of apotable water storage tank . The tank was internally inspected for the first time afterfourteen years of service. Paint blisters and rust spots were observed on the bottomplates. Sand blasting and repainting the bottom plates and shell plates were to be usedas a remedial work .However, during the sand blasting, holes and deep pitting were observed on thebottom plates. On-site visual inspection, magnetic flux leakage (MFL) inspection,ultrasonic testing (UT), and evaluation of the external cathodic protection (CP) systemwere used in the failure analysis. The failure is attributed to the ingress of water and itsimpoundment under the tank bottom along the periphery inside the ring wall and failureof water side epoxy coating.

Keywords

• coating thickness
• corrosion failure analysis
• nondestructive examination