THE STUDY OF INFLUENCE OF THE AREA RATIO VARIATIONS BETWEEN ZINCSACRIFICIAL ANODE AND EH36 SHIP HULL STEEL UNDER CATHODIC PROTECTION CONDITION IN 3.5WT% NACL

• Main Author: Alvian Purnama, Farrel
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/49103
• Institution: Institut Teknologi Bandung

Corrosion in ship hull steel is the most common problem in the shipping industry. Statistical data shows that 90% of hull damage caused by corrosion. The method of preventing corrosion in ship structures through cathodic protection is the best way to prevent corrosion of metal structures in seawater environments. Zinc alloy sacrificial anodes are widely used to protect ships and port structures. Factors that affecting the sacrificial anode cathodic protection in this ship are the distance of the anode to the cathode, the salinity of seawater, area of protection and the length of time of protection. Therefore, this study carried out about comparing the area of the cathode with the anode to the protective conditions in 3.5Wt% NaCl medium. In this experiment, the steel which connected electrically by wire with zinc anode is immersed for 7 days in 3.5Wt% NaCl medium. Determination of the protection criteria is done through a potentiodynamic polarization test and the Electrochemical Impedance Spectroscopy test until an appropriate electrical circuit model is finally obtained. Scanning Electron Microscope testing is done to analyze the surface morphology of the sample. The parameters observed in this study are variations in the area ratio between the sacrificial anode of zinc alloy and EH36 steel, that is, in the ratio of 1: 2, 1: 3, 1: 4. Steels immersed for 7 days are protected by comparing the anode with the cathode 1: 2 had less corrosion product based on SEM results. Based on potentiodynamic polarization experiments, it is required a minimum cathodic protection current of 1.1032 x 10-5 A / cm2 with a potential criteria of -751 mV vs Ag /AgCl. From the cathodic curve of EH36 steel is found that the reaction that occurred was the hydrogen evolution reaction at a protection potential of -1,0269 V, -1,0199V, and- 1,0165V. At the potential criteria of -751 mV it was found that the reaction that occurred was an oxygen reduction reaction. Zinc alloy anode corrosion rate is 0.325 mm/year based on the Tafel plot method. The overall protection potential are unstable, it is caused by IR voltage drop. The decrease in corrosion rate obtained at 1:2 was 67.1474%, which is the highest rate than 1:3 and 1:4. The electric circuit model that is suitable for all conditions is Rs - (CPE1 (Rfilm (CPE2 /Rct))).