VOL. 11, NO. 20, OCTOBER 2016 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences © 2006-2016 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com 12058 CONDENSATION RATE EFFECT ON TOP OF LINE CORROSION IN CO2 ENVIRONMENT Syuhaidah Bt Saufi Anuar, Mokhtar Che Ismail, Pandian Bothi Raja and Noor A’in Binti A. Rahman Department of Mechanical Engineering, Universiti Teknologi Petronas, Bandar Seri Iskandar, Perak, Malaysia E-Mail: syuhaidahsaufi@gmail.com ABSTRACT This research focuses on the effect of condensation rate on top of line corrosion (TLC) for carbon steel (X65) in CO2 environment. The experiment was conducted in a modified glass cell which simulates the TLC phenomena with tested temperature ranging from 25 °C to 55 °C and the cooling temperature was 7 °C. The corrosion rate was measured by the weight loss method and the surface morphology was examined by Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray (EDX). A baseline CO2 corrosion test was also measured simultaneously. The corrosion rate recorded for TLC was in the range from 0.76 mm/year to 1.53 mm/year. Further, the results evident that increase in condensation rate, reduces the corrosion rate which relatively lower than bottom line corrosion rate. The formation of Iron carbonate (FeCO3), which acts as a protective layer is not fully formed and pitting was observed on the surface of the sample. In conclusion, the modified glass cell of TLC experiment was successfully done and it is found that corrosion rate increases with the water condensation rate. Keywords: top of line corrosion, temperature, corrosion rate, carbon steel, CO2, condensation rate. INTRODUCTION Top of Line (TLC) corrosion is an important phenomenon in the oil and gas production industries worldwide and it is particularly prevalent in a number of offshore and onshore operations in Asia Pacific. Regional operators that have experienced TLC corrosion failures or damage or those that are considering its effects on the design stage include Chevron Thailand, Chevron Australia (Gorgon), PTTEP, Total Indonesia, ExxonMobil Malaysia, Shell Sarawak, Tallisman Malaysia, and others [1]. TLC corrosion occurred because of heat exchange between the pipe and colder surrounding which will lead to condensation at the internal upper pipe walls. The condensed water is low in pH, but highly saturated and supersaturated with corrosion products which will increase the pH and formation of iron carbonate will occur [2]. Most of the condensed water drains to the bottom of the pipe due to gravity forces. Continuous injection of inhibitors only can be done at the bottom of the pipe, but not the top and sides which will expose them to a very corrosive environment [3]. The condensed water at the top of line become very aggressive since it combines with carbon dioxide (CO2) and/ Acetic acid (HAc) to form acidic gases. Due to various factors, rate and mechanism of TLC cannot be predicted precisely. Some factors that influence TLC corrosion due to CO2 are the temperature of the gas, the temperature of the pipe wall, the total pressure of the system, the partial pressure of CO2, the gas velocity and the condensation rate which affect the corrosion rate in a complex way [3-6]. In 1991, Gunaltun proposed that the iron concentration in the condensed water dilutes due to the continuous condensation on the existing droplet at the top of line. Failure of applied empirical models in his field cases regarding corrosion prediction made him realized that the prediction of the critical condensation rate is more important than the corrosion [7]. However, he did not mention on how to determine the critical condensation rate. Gunaltun and Larrey concluded that the critical condensation rate lies between 0.15 ml.s/m 2 and 0.25 ml.s/m 2 [8]. Gunaltun emphasizes the importance of studying the condensation rate is essential to TLC corrosion rate. Zhang. Z and his co-workers [7] were studied few parameters that affecting the top of line corrosion such as the effect of temperature and condensation rate on the iron carbonate film. They thought that temperature is one of the important parameters as the protectiveness of the film formed depends on the temperature. While, they found that the protective film was very protective at temperatures greater than 70 ºC. They believed that supersaturation occurs because the condensation rate is too low to remove the ion produced quickly [7]. Besides that, they investigate the effect of gas velocity on TLC and the result is that the corrosion rate increased as the gas velocity increased as well as the condensation rate. However, they did not propose any correlation between the parameters and the corrosion rate and their experimental result is still questionable. Since TLC is one of the most challenging corrosion problems in oil and gas industry, the established TLC mechanism was modelled by several researchers [9-13]. Singer. M. et. al [4] were successfully measured the corrosion rate of the iron sample at a gas temperature of 40 °C and found that the general corrosion rate remains constant at a fairly low value throughout the test compared to the gas temperature of 70 °C. This study is focusing on the effect of condensation rate at controlling temperature from 40 °C to 55 °C, in order to study the properties of film forming and the TLC behavior at low temperature in a modified glass cell by weight loss method. The TLC at ambient temperature also was done for a comparison purpose. Furthermore, the corrosion rate of the bottom of line corrosion also was monitored for a baseline test.