Sang-Ok Chong

Mechanical and electrochemical characteristics in sea water of 5052-O aluminum alloy for ship

Abstract The optimum corrosion protection potentials were examined for 5052-O Al alloy, which is mainly used in ships. Various electrochemical experiments were carried out and the surface morphologies of specimens were observed by scanning electron microscopy (SEM) in order to determine the optimum corrosion protection potential to overcome pitting, corrosion, stress corrosion cracking (SCC), and hydrogen embrittlement in sea water. An optimum protection potential range of −1.3 V to −0.7 V was determined under the application of an impressed current cathodic protection (ICCP) system. The low current densities were shown in the range of −1.3 V to −0.7 V in the electrochemical experiments and good specimen surface morphologies were observed after potentiostatic experiment.

Characteristics Evaluation with Cavitation Condition of 304 Stainless Steel in Seawater Environment

This investigation evaluated the effect of cavitation condition on electrochemical characteristics of 304 stainless steel, which is widely used for marine environment. The cavitation test with time were conducted on 304 stainless steel in seawater solution. Surface morphologies of specimen were observed by scanning electron microscope (SEM) and 3D microscope. Pitting depth, weight loss and damage rate were analyzed after each cavitation experiment. The surface damage was more severe as the current density increased. A dramatical increase in the damage depth and weight loss was observed after 7 hours of cavitation experiment.

Optimum temperature on corrosion resistance for plasma ion nitrided 316L stainless steel in sea water solution

The aim of this research is to investigate the optimum plasma ion nitriding temperature on corrosion resistance in natural sea water for plasma ion nitrided 316L stainless steel. Plasma ion nitriding was conducted at different temperatures of 350, 400, 450, and 500 °C with a mixture of 75% of nitrogen and 25% of hydrogen during 10 h. In conclusion of anodic polarization test, a wide passive potential region and a high corrosion potential were observed at a plasma ion nitriding temperature of 450 °C. Moreover, relatively less damage depth and clean surface micrographs were observed at 450 °C as results of observation of three-dimensional (3D) microscope and scanning electron microscope (SEM) after polarization experiments. In addition, higher corrosion potential and lower corrosion current density were indicated at plasma ion nitrided samples than the value of untreated substrate after Tafel analysis. Hence, plasma ion nitrided at 450 °C in sea water solution represented optimum corrosion resistance among the all the plasma ion nitriding temperature parameters.

Electrochemical Characteristics under Cavitation-Erosion Environment of STS 304 and Hot-Dip Aluminized STS 304 in Sea Water Solution

In this paper, the characteristics of a cavitation-erosion damage behavior on the STS 304 and hot-dip aluminized STS 304 under cavitation environment in sea water solution was investigated. The electrochemical experiments were carried out by potential measurement, anodic/cathodic polarization test, Tafel analysis, and also galvanostatic experiment in current density variables for the samples. The apparatus of cavitation-electrochemical experiment was manufactured in compliance with modified ASTM G-32 standard, with the conditions of sea water temperature of and the measurement, amplitude of . The damage behavior was analyzed by an observation of surface mophologies and a measurement of damage depth by a scanning electron microscope(SEM) and a 3D microscope, respectively, after electrochemical test. After polarization experiment under cavitation environment, much higher damage depths for the hot-dip aluminized STS 304 were observed comparing to the untreated STS 304. In addition, higher corrosion current density in hot-dip aluminized STS 304 presented than that of untreated STS 304 as a result of Tafel analysis.