Authors : J.T. Stephen , A.J. Alawode and O.I. Oluwole
Abstract: The effects of heat treatment on corrosion rates of pipe weldments and pipe-whip restraint devices in saltwater medium were investigated and presented. Mild steel pipes were preheated within temperature range of 30-200�C before respective circumferential welding of single-, double- and triple-passes. Thereafter, pipe weldment zones of 10 mm width were cut out and immersed in saltwater. The corrosion rate of single-pass weldment of as-received pipe immersed in saltwater for 90 days was found to decrease by 8.47 and 20.0% due to pipe preheat at 100 and 200�C, respectively. Also, the corrosion rates of double-pass and triple-pass weldments of as-received pipes were correspondingly higher than the 6.85 mpy value for single-pass weldment of identical as-received by 3.21 and 6.57%. This shows that corrosion rate decreases with increase in pipe preheat temperatures but increases with increase in welding pass. Though, weight loss increases with increase in immersion time, corrosion rate does not follow the same trend due to the concentration of stagnant ions blocking the creation of more ions and thus reducing Fe2+ activities in the solution. Corrosion rate of U-bar specimens was also found to decrease with increase in immersion time and with increase in tempering temperature. The findings of this research work shows that appropriate heat treatment could be used to minimize the corrosion rates of metallic structures in a corrosive medium.
J.T. Stephen , A.J. Alawode and O.I. Oluwole , 2008. Effects of Heat Treatment on the Corrosion Rates of Pipe Weldments and Pipe-Whip Restraint Devices in Saltwater Medium. Journal of Engineering and Applied Sciences, 3: 350-356.