A Study Of Corrosion On The PTA Drum Type Dryer

PTA is also known as Pure Terephthalic Acid, is the upstream chemical product and the production of the main raw material of polyester staple fiber. The manufacturing process is an important part of dryer to contain cobalt acetate, manganese acetate, the TA cake bromide direct heating, drying into a powder state, This requires that dryer work in strong corrosive solution of Br-ion conditions, the refinery often use stainless steel316L steel on a PTA dryer, Maintenance because of corrosion problems are often caused production downtime, Therefore, this type of steel in the presence of Br-ion environment, the corrosion mechanism for the processing of equipment, maintenance, life extension to provide a reasonable basis to develop a viable scheme has positive significance.In this paper, immersion tests, potentiodynamic scan, electrochemical impedance spectroscopy on three austenitic stainless steel-304L、316L、317L were tested and analyzed. The results show that:by soaking experiments, the three materials is proportional to the average corrosion rate and temperature, proportional to the concentration ratio of Br ions, in the same environment in the average corrosion rate of304L>316L>317L. Potentiodynamic scanning electrochemical method,304L stable pssivation is very small and unstable,316L is better than304L, and317L obviously a stable pssivation, the corrosion potential of the three points317L>316L>304L, In electrochemical impedance spectroscopy experiments, relative to the open circuit potential, compared to the size of the three Rt317L>316L>304L, which also verified immersion experiments measured the size of three average corrosion rate. Under the same conditions in the human polarized,317L stable passive film formed on the surface showed a high film resistance Rf to0.5×106Ω.cm2. The304Land316L appeared in the point of corrosion resistance is very small, much smaller than the open circuit potential of impedance.For the PTA dryer, the temperature increase from inlet to outlet, Br-ion concentration decreases, the average corrosion occurred at the ends where more can be used with316L or304L, in the middle, upper middle, middle or lower, often pitting suggested the place where the ability to resist pitting corrosion of the317L instead of316L, and then the use of protective measures.