Study On The Corrosion Resistance Of Carbon Steel Welding Seam Welded By Modified Welding Rod In The Ammonium Sulfite Solution

In order to solve the severe corrosion of welding seam of pulp equipment in the ammonium sulfite solution, the corrosion behavior of the carbon steel welding seam welded by a modified welding rod were studied.According to the mechanism of corrosion and alloying,the corrosion potential of welding seam can be improved by adding Cr,Cu,Ni,so as to arrive at the aim which improving corrosion resisting property of carbon steel welding seam.By means of preliminary examination,the research shows that the welding seam's corrosion potential increased and corrosion current decreased with Ni; the corrosion potential and corrosion current of base metal and steel welding seam which has different Ni content and welding seam welded by J422 steel welding rod was studied in 5-11% (NH4)2SO3 solution at the temperature ranging from 20℃to 80℃;corrosion rate tested by gravimetric method in (NH4)2SO3 solution with different concentration at different temperature and which further prove the result of three electrode galvano chemistry. The metallurgical structure ,surface defect of different welding seam and base metal before the corrosion were gotten by metallographic analysis and stereoscan photograph , the microscopic pattern in corroded condition at different condition was also obtained ,through all of we confirm the effect of structure and defect to the corrosion rate ,and analysed the effect of modified welding rod to the corrosion rate of carbon steel welding seam intuitionisticly, consequently expalined the effect of temperature and density of ammonium sulfite solution to corrosion rate and find the corrosion rule of carbon steel welding seam welded by in the ammonium sulfite solution.The results show that the microscopic structure of Q235 steel was refined after welding by modified welding rod and it's the most important reason for high corrosion resisting property of welding seam which welded by modified welding rod.At the same condition,corrosion rate of welding seam welded by the modified welding rod obviously less than the corrosion rate of the base metal and the welding seam welded by J422 carbon steel welding rod.At the same condition,The welding seam with 1.2%Ni has the best corrosion resistance in the ammonium sulfite solution.