Evaluation of the Corrosion Resistance of Welded Joints of Stainless-Clad 304/Q235B Bimetallic Steel Rectangle Tubes and 304 Stainless-Steel End Plates

Abstract Stainless-clad bimetallic steel, which can balance corrosion resistance and economy, is becoming a new research hot spot in high-performance steel structures. This study focuses on rectangular tube components fabricated from stainless-clad 304/Q235B bimetallic steel plates (with 304 stainless cladding on the outer side) and closed by welding with 304 stainless-steel end plates. This design is to isolate the carbon steel base from corrosive media, achieving corrosion resistance close to that of all-stainless-steel structures. Three welding process schemes are proposed, and mechanical tests and indoor salt spray accelerated corrosion tests were conducted to evaluate the joints. Mechanical property tests show that the maximum hardness value of each joint does not exceed 280 vickers hardness (HV), and their microhardness meets engineering requirements. The joint with the process combination of shielded metal arc (SMA) welding + E309-16 electrode has the best mechanical properties, while the joint with the combination of tungsten inert gas (TIG) welding + ER308 welding wire has the best corrosion resistance. The indoor salt spray accelerated corrosion test indicates that welds promote the occurrence of corrosion, and the intersections of welds are the most susceptible parts to corrosion in tube joints. The weight loss fitting curve shows a power function characteristic, with the fitting coefficient R 2 > 0.98 and the exponent n < 1 , which indicates that the rust layer or passive film plays a partial protective role on the base material. The corrosion prediction model for the welded joints of stainless-clad 304/Q235B bimetallic steel rectangle tubes and 304 stainless-steel end plates in the marine atmospheric environment of Qingdao, China, is as follows: t = 34.9876 T 0.4441 . These findings provide a reference for promoting the application of stainless-clad steel plate structures.