Improvement of the corrosion behavior of AISI 304L stainless steel by deep rolling treatment under cryogenic cooling

The effects of deep rolling parameters, particularly, work speed and cooling conditions (dry and cryogenic) on the surface integrity of AISI 304L machined samples and their further impact on uniform and localized corrosion behavior in chloride environment were experimentally investigated in this work. The electrochemical behavior of machined and deep rolled samples was assessed using cyclic potentiodynamic polarization tests in synthetic seawater. It was found that the corrosion behavior of AISI 304L deep rolled components is related to combined factors: surface roughness, recrystallized grains, strain-induced martensite, microhardness and residual stresses. Findings of this study exhibit that grain refinement generated in the surface layers leads to improved corrosion behavior of deep rolled specimens with regard to machining state. In addition, samples deep rolled at a speed of 25 m/min, without cooling, showed better corrosion resistance than those processed under cryogenic cooling. However, the application of cryogenic deep rolling at speeds of 75 and 120 m/min significantly enhanced the electrochemical behavior of mechanically treated specimens. Despite of high amounts of strain-induced martensite that can deteriorate the electrochemical behavior, it was shown that specimens deep rolled under these conditions, presenting better surface characteristics, depicted an improved corrosion resistance.