Corrosion Resistance of Mechanical Composite Pipe End

The microstructure observation, chemical composition analysis and evaluation of intergranular corrosion resistance and pitting corrosion resistance of 316L/X65 bimetal mechanical composite pipe end used for oil and gas pipeline were carried out. The results showed that the cladding layer at the end was divided into two layers, the microstructure was columnar dendritic austenite, the grain of the outer layer was smaller than that of the inner layer, and the outer layer had good corrosion resistance. The intergranular corrosion resistance of the pipe end of the composite tube met the engineering application requirements. The pitting resistance from weak to strong can be ranked as 316L Inconel625, 316L liner tube and Inconel625 surfacing layer. The pitting resistance of the pipe end would be significantly reduced when the temperature rised. The 316L at the joint of 316L liner and Inconel625 surfacing layer were more susceptible to corrosion due to the galvanic effect.