Atmospheric corrosion of welded dissimilar T-joints made of steel and improvements in the corrosion prediction model

This paper investigates the corrosion behaviour of dissimilar T-joints made of duplex stainless steel and carbon steel under atmospheric environments. Stainless steel grade EN1.4062 was welded to two different carbon steel grades, S355J2 and P460NL2, via gas metal arc welding to form T-joints. The fabricated specimens were subjected to 12-month exposure tests in four mildly corrosive environments distributed across 3 different European countries: Belgium, England, and Portugal. Uniform, galvanic, and pitting corrosion was observed and analysed in detail. In particular, the CS plates, nearby HAZs, and junctions between the SS and CS plates are areas with relatively low corrosion resistance. This finding provides guidance for the use of protective coating systems for dissimilar weldments. The evaluation of corrosion rates obtained in this study and from previous literature suggests that some prediction models are too conservative for atmospheric corrosion under mildly corrosive environments. Two mathematical functions for corrosion rate prediction have thus been recalibrated from a newly formulated corrosion database. A model with the best accuracy for carbon steel under similar conditions is finally identified.