Corrosion behavior of Ni20Cr coatings deposited by HVOF (high velocity oxygen-fuel) process was evaluated in ZnCl2-KCl (1 : 1 mole ratio) molten salts. Electrochemical techniques employed were potentiodynamic polarization curves, open circuit potential, and linear polarization resistance (LPR) measurements. Experimental conditions included static air and temperatures of 350, 400, and 450°C. 304-type SS was evaluated in the same conditions as the Ni20Cr coatings and it was used as a reference material to assess the coatings corrosion resistance. Coatings were evaluated as-deposited and with a grinded surface finished condition. Results showed that Ni20Cr coatings have a better corrosion performance than 304-type SS. Analysis showed that Ni content of the coatings improved its corrosion resistance, and the low corrosion resistance of 304 stainless steel was attributed to the low stability of Fe and Cr and their oxides in the corrosive media used.
The corrosion phenomenon in oil and gas industry is a serious issue affecting metallic structures and pipelines. The main aggressive species flowing through oil pipelines is NaCl. The presence of gases in the corrosive medium (CO 2 and H 2 S), increases, even more, its aggressiveness. Usually, to mitigate corrosion, liquid inhibitors are added to the corrosive medium. In the present study, N-hydroxyethyl-imidazoline derivatives of avocado oil was synthesized as a green corrosion inhibitor. The test was performed on 1018 carbon steel at 5, 10, 25, 50 and 100 ppm. Electrochemical techniques as polarization curves (PC), the open circuit potential (OCP), the lineal polarization resistance (LPR) and the electrochemical impedance spectroscopy (EIS) were applied. The results obtained from the OCP indicates that the inhibitor can be classified as a cathodic type one. On the one hand, PC, RPL and EIS determined that the highest corrosion rate was obtained without the inhibitor. On the other hand, by adding inhibitor, the corrosion resistance increased, obtaining the optimal concentration at 10 ppm. The EIS technique in the angle phase format showed the formation of two time constants, which indicates the inhibitor presence. Finally, the SEM analyses showed a minor attack at 5 and 10 ppm.
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