ABSTRACT Water cooling systems usually receive additional chemical treatment and different features to prevent pitting corrosion on stainless steel which is dependent on medium factors such as species concentration. Chloride is an aggressive ion with which sulfate can act as an inhibitor. By applying cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and Mott-Schottky plots, the behavior of 304 stainless steel (304 SS) was evaluated in solutions containing chloride, sulfate and ammonium ions. The polarization curves indicated the inhibiting effect of sulfate ions against pitting corrosion and the increase of the repassivation potential with increasing ammonium concentration. The most pronounced inhibiting effect occurred with a smaller ratio between chloride and sulfate ions (1:2). By EIS, the values obtained for charge transfer resistance of 304 SS sample corroborated the results of the cyclic voltammetry, ranging between 0.4 and 0.7 MΩcm2. The passive film showed semiconductor behavior, in agreement with the model of the chromium oxide inner layer and iron oxide outer layer. The passive films formed were highly doped, with doping density values on the order of 1020-21 cm–1. The difference between the corrosion potential and the flat band potential was found in the solutions where the material was less susceptible to corrosion.

The aim of this study was evaluate, two methods for the detection and identification of sulphate reducing bacteria (SRB): ML medium and PCR with specific primers for SRB groups. SRB were detected through the selective medium only on carbon steel, which showed corrosion. Employing specific PCR primer, SBR were detected from all the metallic components assayed, even those that did not present visible corrosion spots, such stainless steel and copper alloys. Despite the presence or absence of corrosion at the later stages effectively by using the selective medium,, the initial stages of the corrosion could only be detected by the amplification of total DNA with SRB specific primers. The early detection of SRB could be employed for preventing the damages on metal surfaces before the installation of corrosion processes. Strategies for reducing the time spent on SRB isolation and identification could be auxiliary tools for controlling the corrosion of materials.

The influence of natural aging furthered by atmospheric corrosion of parts of electric transformers and materials, as well as of concrete poles and cross arms containing corrosion inhibitors was evaluated in Manaus. Results for painted materials, it could showed that loss of specular gloss was more intensive in aliphatic polyurethane points than in acrylic polyurethane ones. No corrosion was observed for metal and concrete samples until 400 days of natural aging. Corrosion in steel reinforcement was noticed in some poles, arising from manufacturing faults, such as low cement content, water/cement ratio, thin concrete cover thickness, etc. The performance of corrosion inhibitors was assessed by many techniques after natural and accelerated aging in a 3.5% saline aqueous solution. The results show the need for better chemical component selection and its concentration in the concrete mixture.