Abstract

Zinc (Zn) coating is being used to protect steel structures from corrosion. There are different processes to deposit the coating onto a steel substrate. Therefore, in the present study, a 100 µm thick Zn coating was deposited by arc and plasma arc thermal spray coating processes, and the corrosion resistance performance was evaluated in artificial seawater. Scanning electron microscopy (SEM) results showed that the arc thermal spray coating exhibited splats and inflight particles, whereas plasma arc spraying showed a uniform and dense morphology. When the exposure periods were extended up to 23 d, the corrosion resistance of the arc as well as the plasma arc thermal spray coating increased considerably. This is attributed to the blocking characteristics of the defects by the stable hydrozincite (Zn5(OH)6(CO3)2).

Highlights

  • The surface of a steel structure must be protected from corrosion due to exposure to open atmosphere or controlled laboratory conditions

  • The bonding ability of the Zn coating deposited by the plasma arc thermal spray process was 26.37% greater than that deposited by the arc thermal spray process

  • The present study explained the corrosion kinetics and the mechanism of dissolution of the Zn coatings, the nucleation and growth of corrosion products on the coatings, and the blocking characteristics of defects by the corrosion products on the coatings that were deposited by the arc thermal spray and plasma arc thermal spray processes, after being kept in artificial seawater for different periods of exposure

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Summary

Introduction

The surface of a steel structure must be protected from corrosion due to exposure to open atmosphere or controlled laboratory conditions. This is achieved by the deposition of a metal coating onto the steel substrate. Zinc (Zn) metal is widely used as it acts as a barrier and provides cathodic protection as well [1]. It is used in construction, automobiles, electrical engineering, marine engineering, and petrochemicals as it is anodic in nature and proven to be economical [2,3,4]. The protective action of Zn lies in its reaction with atmospheric compounds such as O2 , H2 O, and CO2 , whereby dense, adherent, and insoluble corrosion products that isolate Zn from the atmosphere and act as barriers against the ingress of aggressive ions are formed

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