Effects of metal cations on corrosion of mild steel in model fresh water

Abstract

The effects of metal cations on corrosion of mild steel in model fresh water were investigated by electrochemical techniques and immersion tests. Analysis of X-ray photoelectron spectroscopy showed that metal cations have large hardness of cations, X, are incorporated in passive films. The electrochemical and immersion results showed that X is not suitable as a corrosion indicator of mild steel. A novel corrosion indicator, "corrosion inhibitory effect of cations Y", that consists of X and molar volume ratio, ∆V, is proposed, and it is shown that the novel indicator can estimate the corrosion rate of mild steel in fresh water.

Inhibition Ability of Gluconates for Fresh Water Corrosion of Mild Steel Enhanced by Metal Cations

“…These clear grain boundaries mean that intense uniform corrosion occurred on the mild steel in NaA solution. 26 Pits on the specimen are observed after immersion in NaG solution ( Fig. 2 (c)).…”

“…9 (d)). It has been also shown that metal cations that have large ∆V would form the defectless and highly protective layer on mild steel, 26 therefore, the metal cation layer of Zn 2+ would have good protective ability against Cl -attack in the solution. For these reasons, Zn 2+ with large Y would contribute to the enhancement of the inhibition ability of gluconates for mild steel in fresh water.…”

“…The values of Y, X, and ∆V of Zn 2+ are larger than those of other metal cations shown in Table 1. Several studies 26,32,33 have shown that metal cations that have large X can easily bond with OH -on the oxide films of mild steel and in the gluconates adsorbed on the oxide film. For this reason, Zn 2+ would bond to the oxide film at the defect sites and to the protective films of gluconates ( Fig.…”

“…ΔV indicates the tendency of protective ability against corrosion of the metal cation layer formed on the mild steel. 26 Y, X, and ∆V of the metal cations which were calculated by equations (1) Figure 4 shows XPS narrow spectra of C 1s on specimens after immersion for 7 d in model fresh water. The C 1s spectra could be deconvoluted into three peaks (285.0 eV, 287.0 eV, and 288.5 eV), indicating three chemical forms of C present on the mild steel surface.…”

“…Research focused on the effects of metal cations 26 showed that the corrosion rate of mild steel in fresh water decreases with an increase in the novel indicator of metal cations corrosion inhibitory effect of cation, Y. Therefore, it can be estimated that the inhibition ability of gluconates for fresh water corrosion would be enhanced by metal cations that have large Y in fresh water.…”