Characteristics of Calcareous Films Formed by Using Pulse Electrodeposition Method in Natural Seawater

Abstract

Due to the characteristics of seawater as the most environmentally corrosive electrolyte solution, using the cathodic protection method while taking it into consideration widely prevails in offshore and underwater structures. Cathodic protection is type of method polarizing the surface of the corrosive metal to reduce the corrosion rate. When this principle is applied, the ionic component that is dissolved in seawater can be deposited partially when Mg(OH)2 and CaCO3 compound to coat an electrodeposited film on the metal surface. These electrodeposition films are called as ‘calcareous deposits,’ which act as a physical barrier and they function to reduce the density of the cathodic protection current, which eventually leads to an anti-corrosion effect. However, these films, on the other hand, are influenced to large extent by the condition of surrounding environment when formed as well as the condition of deposits components, which are neither dense nor uniform. In this study, the pulse electro-deposition method was applied to make calcareous deposits film in natural seawater. The components and structures are, then, analyzed by using Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The amounts of the formed film, adhesion, and corrosion resistance were evaluated individually to prove its effectiveness. This study validated the effectiveness of the pulse electrodeposition method and considered the formation mechanism of the calcareous deposits film through analysis and evaluation results. In addition, this study also confirmed the potential for improving the performance of existing calcareous films that showed weak durability by controlling the pulse current.