Study On The Corrosion Electrochemical Properties Of TTS443Ferritic Stainless Steel

In recent years, high chromium, nickel-free ferritic stainless steel has been rapidly developed because of the rising prices of nickel. Ferritic stainless steel can be used in many areas, such as household products, auto parts, building decoration, electronic devices and so on. At same time, it has great value and market potential in some other area because of its ferromagnetic properties, high thermal conductivity, low thermal expansion coefficient, high yield strength, small strain hardening tendency and other significant characteristics.TTS443stainless steel developed by Taiyuan iron and Steel Group, and it contains21%chromium, has no nickel and molybdenum, with good formability and weldability, can replace the304austenitic stainless steel in many fields. In this way, not only can take advantage of its excellent performance, but also can save nickel resources. But as a new material, the date about its corrosion resistance and its advantages are not completed as there have no much research about this stainless steel.In this paper, the influence of mass fraction of chloride ion and acidity on the corrosion rate and pitting corrosion resistance of TTS443stainless steel have been studied by means of polarization curves, cyclic polarization curves and electrochemical impedance spectroscopy (EIS). And compared with the corrosion of304austenitic stainless steel that under the same conditions, conclusions are as follows:In NaCl solutions, with the increase of mass fraction of chloride ion, the pitting potential (Eb) of TTS443stainless steel decrease first and then increase, and corrosion current (Icorr) increase first and then decrease, in12%NaCl solution, the resistance of passive film was smaller, capacitance was the maximum, the corrosion rate was the fastest, the pitting corrosion resistance was the weakest. While in HCl solution, with the increase of concentration, the corrosion rate was increased, the value of Eb reduced, and it can change the structure of passive film from double-layer to monolayer. Under the same conditions of chloride ion, the corrosion rate under acidic medium was faster than neutral medium.With the increase of mass fraction of chloride ion and hydrogen ion, the corrosion current of304increased, the pitting potential decreased. The corrosion of304in sodium chloride solution was controlled by the diffusion rate of oxygen. And it was controlled by hydrogen ion in low concentration of hydrochloric acid solution, the corrosion rate will be faster when hydrogen ion increased.Under the same conditions of chloride ion, the corrosion rate of TTS443stainless steel was slower than304,but the pitting corrosion resistance is weaker; At the same time, in seawater, the corrosion rate of TTS443stainless steel was slower than304. Under the same conditions of acidity, compared with304stainless steel, the corrosion rate of TTS443stainless steel was faster, and the pitting corrosion resistance was weaker.