Several Brazilian offshore pipelines are made of duplex stainless steel. In the welding processes, the oxygen content in back purging gas is controlled to prevent oxidation on the inner surface of welded joints. Understanding how the pitting corrosion resistance is affected by a higher oxygen level and how a post-weld surface treatment by pickling and passivation can improve the corrosion resistance is important in situations where the control of oxygen content is limited. In the present study, specimens welded with back purging gas containing 100 ppm and 200 ppm of oxygen and without back purging gas were investigated through ASTM(1) G48 A, and through corrosion tests under field simulated conditions. In these two last weld conditions, the specimens were also investigated after pickling and passivation treatments. No significant mass loss was observed and no pit was verified for 100 ppm. Without back purging gas and for 200 ppm of O2, the pitting resistance were improved after post-weld surface treatment.

Subject
Pickling, Mass loss, Penetrants, Welding, Micrography, Surface treatments, Purging, Pitting, Passivation, Ports and harbors, Oxygen, Corrosion resistance, Corrosion coupons
Keywords:
Duplex stainless steel, Welding, Back purging gas, Corrosion resistance, Post-weld treatment
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2023
Association for Materials Protection and Performance (AMPP)
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