Anodic layers have been grown on 304L stainless steel (304L SS) using two kinds of fluoride-free organic electrolytes. The replacement of NH₄F for NaAlO₂ or Na₂SiO₃ in the glycerol solution and the influence of the H₂O concentration have been examined. The obtained anodic layers were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and potentiodynamic polarization tests. Here, it was found that, although the anodic layers fabricated within the NaAlO₂-electrolyte and high H₂O concentrations presented limited adherence to the substrate, the anodizing in the Na₂SiO₃-electrolyte and low H₂O concentrations allowed the growth oxide layers, and even a type of ordered morphology was observed. Furthermore, the electrochemical tests in chloride solution determined low chemical stability and active behavior of oxide layers grown in NaAlO₂-electrolyte. In contrast, the corrosion resistance was improved approximately one order of magnitude compared to the non-anodized 304L SS substrate for the anodizing treatment in glycerol, 0.05 M Na₂SiO₃, and 1.7 vol% H₂O at 20 mA/cm² for 6 min. Thus, this anodizing condition offers insight into the sustainable growth of oxide layers with potential anti-corrosion properties.

Different chemical and physical treatments have been used to improve the properties and functionalities of steels. The anodizing is one of the most promising treatments, due to its versatility and easy industrial implementation, since it allows obtaining different microstructures on the surface, in order to be employed in different industrial sectors. The present work has studied the influence of the anodizing time (15, 30, 45 and 60 min), as well as the stirring speed (0, 200, 400 and 600 rpm), on the morphology and the resistance corrosion behavior of anodic layers grown in 304L stainless steel. The anodic layers were characterized morphologically, compositionally and electrochemically, in order to determine the influence of these parameters on their corrosion behavior in a 0.6 M NaCl saline solution. The results show that the generation of anodic layers at different times propitiates the definition of nonporous morphologies, while the phenomena of dissolution of the layers that increase with the time of anodizing. However, the resistance to corrosion decreases respect to the non-anodized 304L SS. On the other hand, the effect of the stirring speed during the generation of these anodic layers does not seem to influence the corrosion behavior in the saline medium studied.