Yong-Sang Kim

Computational Interpretation of the Relation Between Electric Field and the Applied Current for Cathodic Protection Under Different Conductivity Environments

An interpretation of the relation between the electric field and the applied current for cathodic protection is investigated using a boundary element method simulation. Also, a conductivity-difference environment is set for the interface influence. The variation of the potential distribution is increased with the increase of the applied current and the conductivity difference due to the rejection of the current at the interface. In the case of the electric field, the tendencies of the increasing rate and the applied currents are similar, but the interface influence is different according to the directional component and field type (decrease of Ez and increases of Ex and Ey) due to the directional difference between the electric fields. Also, the change tendencies of the electric fields versus the applied current plots are affected by the polarization curve tendency regarding the polarization type (activation and concentration polarizations in the oxygen-reduction and hydrogen-reduction reactions). This study shows that the underwater electric signature is determined by the polarization behavior of the materials.

Effect of 1, 2, 3-benzotriazole on the corrosion properties of 316L stainless steel in synthetic tap water

This study examines the effect of the benzotriazole on the corrosion properties of 316L stainless steel in synthetic tap water. Electrochemical tests, surface analyses and quantum study were conducted for evaluating corrosion behavior and adsorption mechanism. In case of stainless steel in the synthetic tap water, the adsorption layer of benzotriazole is not uniform due to the low adsorption. The benzotriazole is preferred to ionic state in alkaline condition like synthetic tap water. Thus, the formation of metal-benzotriazole complex was difficult, and which confirmed in FT-IR analysis. The ionic state of benzotrizole in alkaline environment caused the electrostatic repulsion force and the strong tendency of donating electron obstructed the adsorption of ionic benzotirzole. In addition, the lack of d-orbital of Cr made hard to adsorption of the benzotrizle on the stainless steel. This non-uniform adsorption layer of benzotriazole on the stainless steel surface induced the localized defect sites which decrease the pitting resistance of stainless steel.

Effects of Post Weld Heat Treatment on Mechanical and Electrochemical Properties of Welded Carbon Steel Pipe

To prevent a failure caused by stress corrosion cracking (SCC) of welded carbon steel pipe in district heating systems within service life, the effects of post weld heat treatment (PWHT) on the mechanical, electrochemical properties and resistance of SCC were investigated. As the result of normalized treatment, Vickers hardness, yield strength and tensile strength decreased, but ductility increased. Electrochemical properties were evaluated using potentiodynamic polarization tests and electrochemical impedance spectroscopy. Uniform corrosion was observed on all specimens, although the corrosion rate was slightly increased by PWHT. The resistance of SCC was evaluated using slow strain rate test under the accelerated corrosion condition. The resistance of SCC was increased by PWHT, especially by normalized treatment. If the reduced strength by PWHT satisfies the design stress, it is possible to decrease the probability of failure within service life in welded pipeline by normalized treatment.

Influence of Ultrasonic Nanocrystal Surface Modification on the Corrosion and Stress Corrosion Cracking Behavior of Low Carbon Steel (ASTM A139) Welded Joint in the Simulated District Heating Environment

The effect of ultrasonic nanocrystal surface modification (UNSM) on the corrosion and stress corrosion cracking behavior of low carbon steel (ASTM A139) welded joint in the simulated district heati...

Evaluation of corrosion fatigue and life prediction of lower arm for automotive suspension component

Lower arm is one of the suspension components of automobile. It is suffered from driving vibration and corrosive environment, namely corrosion fatigue. In this study, corrosion fatigue property of lower arm was investigated, and a modified model based on Palmgren-Miner rule was developed to predict the lifetimes of corrosion fatigue. The corrosion fatigue life of lower arm was about 1/6 times shorter than fatigue life. Based on the results of corrosion fatigue tests and meteorological data in Seoul and Halifax, the corrosion fatigue life of lower arm was predicted. The satisfaction of 10-year and 300,000 km warranty was dominated by the climate of automobile driving. This prediction indicates that the weather condition or driving condition influences the life of automotive parts. Therefore, to determine the warranty of automotive parts, the driving condition has to be carefully considered.