Effect of corrosion on the tensile strength of structural steel (UNS G10170) exposed to seawater

Abstract

Carbon steel is the most widely used engineering material and despite its relatively limited corrosion resistance, is used in large tonnages in marine applications, chemical processing, petroleum production and refining, pipelines, etc. The corrosion of carbon steels is a problem of enormous practical importance because the cost of metallic corrosion to the total economy of the world runs into hundreds of millions of dollars per year. This work was carried out to study the effect of corrosion on the mechanical properties of structural steel (UNS G10170) exposed to seawater. Steel samples were subjected to normalising heat treatment, before being immersed in seawater at 15 days intervals for duration of 90 days. The corrosion rates of the steel samples were determined by the weight loss method. The results showed a 9.00% decrease in hardness for the as received sample and 6.50% decrease for the normalised sample; 12.23% decrease in tensile strength for the as-received sample and 7.90% decrease for the normalised sample respectively at the end of the 90^th day.  It was found that ferrite was less noble than cementite, which caused it to sacrificially dissolve once the samples were polarized in the sweater environment thereby leading to loss of material (weight loss) and consequently reduction in mechanical properties