Influence of Heat Treatment Process on Carbon Steel Pipe Corrosion in The Presence of Carbon Dioxide, CO2 and Acetic Acid, HAc

Carbon steel is the cheapest and the most versatile materials for pipeline. During fabrication of the pipeline, carbon steel will undergo specific heat treatment to serve their specific purposed. Heat treatment is a process of modification of the microstructure by heating and cooling of the metals to achieve desired physical and mechanical properties. In carbon dioxide (CO2) environment, the corrosion product, Iron Carbonate (FeCO3) will form as the iron ion (FE2+) in the carbon steel reacted with the bicarbonate anion (CO32-) from the dissolved CO2. Previous study has shown that difference in heat treatment will give difference in corrosion rate. In the presence of Acetic Acid (HAc), it will act as catalyst for CO2 corrosion where it will affected the pH value. Thus it will cause the corrosion product to from faster. The objective of this project, it is to study the influence of heat treatment process on carbon steel pipe corrosion in the presence of Carbon Dioxide and Acetic acid. The experiments were conducted by using an X-65 Carbon Steel pipe. The sample have undergo further heat treatment process which were annealing, normalizing and quenching. The corrosion rate measuring technique used was Linear Polarization Resistance (LPR) and Weight Lost (WL). Three-electrode glass cell experiment and immersion test were conducted. An investigation by using Optical microscope was conducted to determine the microstructure of each samples. For annealing, the microstructure appear to be coarse pearlite, normalizing to be fine pearlite while quenching form a martensite microstructure. From the analysis of corrosion rate, annealing showed the lowest corrosion rate compared to other type of heat treatment. This concluded that annealing have the highest corrosion resistance. The result also showed that 1000ppm of acetic acid caused the corrosion rate to increase up to 50 percent for each sample regardless of the heat treatment applied.