Effect of pH on the Corrosion and Repassivation Behavior of TA2 in Simulated Seawater.

Yingxiao Zhang,Xiaogang Li,Longfei Song,Zhiyong Liu,Tingting Yan,Lin Fan

doi:10.3390/ma14226764

Abstract

The effect of pH on the corrosion and repassivation behavior of TA2 in simulated seawater was studied using electrochemical tests, immersion experiments, and surface morphology topology analysis. The results show that Ecorr and Rf increased while ipass and weight loss rate decreased as the pH of simulated seawater increased. The TA2 passive film was determined to be mainly composed of a large amount of TiO2 and a small amount of TiO. The repassivation function of TA2 can be expressed as E = −0.1375 + 0.0532ln(t − 1.241) for a simulated seawater pH of 8.2. The parameter b, which represents the slope of the potential–time curve during the friction electrode test, was used to evaluate the repassivation behavior of TA2. The increase in pH value was observed to promote the repassivation speed of the passive film, which is beneficial to the corrosion resistance of TA2.

Highlights

National Materials Corrosion and Protection Data Center, University of Science and Technology Beijing, State Key Laboratory for Marine Corrosion and Protection, Luoyang Ship Material Research
The passivation zone starts at about 0 V, and the breakdown potential was not observed during the test
This range is considerably wide compared with other passive metals such as 316 L stainless steel [20], 2205 duplex stainless steel [21], and Ni(Fe, Al)-maraging steel [22], and was due to the protection of the passive film on the metal substrate surface

Summary

Introduction

National Materials Corrosion and Protection Data Center, University of Science and Technology Beijing, State Key Laboratory for Marine Corrosion and Protection, Luoyang Ship Material Research. The increase in pH value was observed to promote the repassivation speed of the passive film, which is beneficial to the corrosion resistance of TA2. The surface of titanium can quickly form a dense, well-covered and difficult-to-dissolve passive film. This passive film mechanically separates the metal from seawater, greatly lowering the metal dissolution rate, and has excellent self-repairing ability [8,9]. The corrosion resistance of titanium depends on the integrity of the passive film on the surface and its self-repairing ability after rupture. Gou et al [14] prepared a titanium-containing conversion coating on an AZ91 alloy and found that the increase in pH value promoted a decrease in the coating thickness and crack number, improving the corrosion resistance

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Conclusion