Study On Corrosion Behavior Of TA31 Alloy In Hydrochloric Acid Solution

The environment of offshore oil exploitation and the acid oilfield exploitation in southwest China generally has the characteristics of strong corrosion,so the corrosion resistance of alloy seamless pipe is more and more demanding.Titanium alloy has become an ideal material for this harsh environment because of its excellent comprehensive properties.However,in such a harsh environment,the corrosion resistance of titanium alloys is far from sufficient.Therefore,it is necessary to grasp the corrosion behavior of titanium alloys in this environment,and to study the factors affecting the corrosion resistance of titanium alloys,and find ways to improve the corrosion resistance of titanium alloys.In this paper,TA31 alloy was used as experimental material,and different cold deformation and heat treatment were carried out.The corrosion behavior of TA31 alloy in hydrochloric acid solution after different treatments was observed,and the factors affecting the corrosion resistance of TA31 alloy were discussed.The cold-rolling deformation of the bi-modal microstructure TA31 alloy and the layered TA31 alloy was carried out.The electrochemical corrosion test and immersion corrosion test showed that the corrosion resistance of the two alloys in hydrochloric acid solution increased with the increase of cold rolling deformation.After cold rolling,the dislocation density of the alloy increases to form substructures,and the grains are elongated and even broken in the rolling direction,and the grain size of the alloy as a whole becomes smaller,which increases the number of grain boundaries in the alloy.It provides more nucleation sites for the formation of TA31 alloy passivation film and improves the corrosion resistance of TA31 alloy.By analyzing the passivation film of TA31 alloy,it can be seen that the passivation film of TA31 alloy is not a single layer structure,but a multi-layer structure based on Ti oxide and containing Al,Nb,Zr,Mo element oxides.The TA31 alloy seamless tube with rolled original structure was annealed at different temperatures and cooled at different rates.It was found that the corrosion resistance of TA31 alloy in hydrochloric acid solution first decreased and then increased with the increase of annealing temperature by electrochemical corrosion test and immersion corrosion test.The corrosion resistance of TA31 alloy after quenching treatment is the best,followed by furnace cooling treatment.The air cooling has the worst corrosion resistance.The ?/? phase content and grain size are considered to be the cause of this phenomenon.It is found by the first principle calculation that the ? phase is more likely to form the microgalvanic cells than the ? phase,which accelerates the corrosion of the ? phase.