Effect of salinity on the corrosive wear behaviour of engineering steels in aqueous solutions

Abstract

The effect of salinity is assessed on the corrosive wear behaviour of a low-alloy steel (UNS G43400) and three stainless steels (UNS S15500, UNS S31600 and UNS S32760). Erosion-corrosion testing was conducted using a submerged impingement slurry jet test-rig. Three salinities were evaluated; 0.05%NaCl, 3.5%NaCl and 10%NaCl. Total volume losses (TVL) and a volumetric analysis technique were used to assess the damage in the directly-impinged zone (DIZ) and outer area (OA). Under all measured parameters, material loss for the stainless steels increased marginally with increased salinity. In terms of TVL and OA volume loss, the low alloy steel exhibited significantly greater material loss from 0.05%NaCl to 3.5%NaCl conditions, however, no further increase was evident when the salinity was raised to 10%NaCl.

Erosion-Corrosion Mechanisms of Engineering Steels in Different NaCl Concentrations

“…Impressed current cathodic protection (ICCP) tests were also performed to isolate the pure mechanical damage by maintaining the electrode potential at -800 mV using an Ag/ AgCl reference electrode. Back extrapolation of the anodic polarisation curves at this potential demonstrated that the residual anodic reaction rates were negligible, as has been observed in a previous study [22].…”

“…In summary, it appears that the use of a single specimen to obtain damage trends in most submerged jet experiments is likely to yield imprecise findings in some circumstances-especially in relation to the attack on the directly impinged zone. This feature has been noted in previous investigations [21][22][23]40]. It is worthwhile noting that there is reasonable correlation between the material loss of single samples and the outer area.…”

“…The pure sliding abrasion damage of the materials was calculated by subtracting the erosion damage in the DIZ under cathodic protection conditions from the total volume loss. The sliding abrasion damage has been illustrated in previous work [22]. Although there is often a link between high hardness and improved sliding abrasion resistance, the lowalloy steel, which exhibited the second greatest hardness, was found to have the poorest sliding abrasion resistance.…”

“…For the low-alloy steel, the corrosion-enhanced abrasion mechanisms can be attributed to the corrosion pits which are formed, as illustrated in a previous related study [22]. The pits cause local turbulence which enhances the mechanical erosion damage.…”

“…In a previous paper [22], the focus was on the role of salinity on the overall material losses -as expressed by Eq. (1).…”