Preparation and characterization of electrolytic alumina deposit on austenitic stainless steel

Conversion coating modified by alumina has been studied as a way for improving the resistance to thermal oxidation of an austenitic stainless steel. Conversion coating, characterized by a particular morphology and strong interfacial adhesion with the substrate, facilitate the electrochemical deposition of ceramic layers and enhance their adhesion to the substrate. The influence of the current density and treatment time on alumina deposit was studied using statistical experimental designs like Doehlert uniform shell design. After heating, coatings present a continuous composition gradient with refractory compounds at the surface. The behavior at high temperature (1000 8C) of the alumina coating was investigated. The presence of alumina increases the oxidation resistance of an austenitic stainless steel at 1000 8C. The morphology and the chemical composition of the deposit are analyzed. Results on the thermal stability of coating on austenitic stainless steel are presented

Temperature Effect on the Corrosion Behaviour of Alloy 31 in polluted H3PO4 and Analysis of the Corrosion Products by Laser Raman Microscope

[EN] Electrochemical behaviour of Alloy 31, a highly alloyed austenitic stainless steel (UNS N08031), in a 40 wt.% H3PO4 solution polluted with 2 wt.% H2SO4, 0.06 wt.% KCl and 0.6 wt.% HF was evaluated by cyclic potentiodinamic curves at different temperatures (20, 40, 60 and 80 degrees C). Temperature was found to favour both cathodic and anodic reactions. The corrosion products forming on the surface of Alloy 31 were indentified in situ by Laser Raman microscope. Corrosion products were mainly iron and chromium oxides, although phosphates were also included as a corrosion product on the surface of Alloy 31.Authors express their gratitude to the MAEC of Spain (PCI Mediterráneo C/8196/07, C/018046/08, D/023608/09 and D/030177/10), to Programa de Apoyo a la Investigación y Desarrollo de la UPV (PAID-06-09) and to the Generalitat Valenciana (GV/2011/093) for the financial support, to Ministerio de Ciencia e Innovación for its help in the Laser Raman Microscope acquisition (UPOV08-3E-012) and to Dra. Asunción Jaime for her translation assistance.Escrivá Cerdán, C.; Blasco-Tamarit, E.; García-García, D.; Garcia-Anton, J.; Ben-Bachir, A. (2012). Temperature Effect on the Corrosion Behaviour of Alloy 31 in polluted H3PO4 and Analysis of the Corrosion Products by Laser Raman Microscope. International Journal of Electrochemical Science. 7(7):5754-5764. http://hdl.handle.net/10251/61165S575457647

Corrosion behaviour of micro-plasma arc welded stainless steels in H3PO4 under flowing conditions at different temperatures

[EN] This paper studies the general corrosion behaviour of the micro-plasma arc welded AISI 316L stainless steel in phosphoric acid at different temperatures (25-60°C) and at a Reynolds number of 1456. Galvanic corrosion has been studied using zero-resistance ammeter (ZRA) measurements and polarization curves (by the mixed potential theory). Results show that the microstructure of the stainless steel is modified due to the micro-plasma arc welding procedure. Coupled current density values obtained from polarization curves increase with temperature. ZRA tests present the highest iG values at 60°C; however, the values are very close to zero for all the temperatures studied. This is in agreement with the low value of the compatibility limit and of the parameter which evaluates the importance of the galvanic phenomenon. Both techniques present the most positive potentials at the highest temperature. This study reveals that micro-plasma arc welded AISI 316L stainless steels are appropriated working in the studied H3PO4 media from a corrosion point of view for all the temperatures analysedThe authors would like to express their gratitude to the Spanish MAEC (PCI Mediterráneo C/8196/07, C/018046/08, D/023608/09) and to Asuncion Jaime for her translation assistance.Sánchez Tovar, R.; Montañés Sanjuan, MT.; García Antón, J.; Guenbour, A.; Ben Bachir, A. (2011). Corrosion behaviour of micro-plasma arc welded stainless steels in H3PO4 under flowing conditions at different temperatures. Corrosion Science. 53(4):1237-1246. https://doi.org/10.1016/j.corsci.2010.12.017S1237124653

Corrosion inhibition of a 70/30 cupronickel in a 3% NaCl medium by various azoles

The cathodic behaviour of a 70Cu-30Ni alloy in a 3% NaCl solution was studied by potential-current curves. It was shown that the corrosion current of the studied alloy increased with the rotation speed of the electrode

Alliage 904 L : comportement électrochimique en milieux phosphoriques pollués par les ions sulfures et fluorures en condition de corrosion-abrasion

La corrosion-abrasion de l’acier austénitique 904 L (X1NiCrMoCu 25-20-5) en milieu phosphorique pollué par les ions sulfures et fluorures a été étudiée par des techniques électrochimiques et physiques.L’étude quantitative de la corrosion-abrasion a montré que la perte de masse totale du matériau résulte essentiellement de l’effet mécanique et de l’action de synergie entre corrosion et abrasion. Dans ces conditions, l’addition des ions sulfures et fluorures dans le milieu électrolytique entraîne une activation de la dissolution et une altération de la passivité (corrosion localisée). Ces effets s’accentuent avec l’accroissement de la teneur du milieu en impuretés.Les informations obtenues sur le film de passivité par les techniques d’analyse de surface (SIMS et EDS) ont révélé la présence des ions sulfures et fluorures dans le film formé

Effect of mineral compounds in phosphoric acid polluted by sulphide ions on corrosion of nickel

The inhibiting effects of two mineral compounds on corrosion of nickel in phosphoric acid (H3PO4) polluted by sulfide ions (S2−) was studied using electrochemical and spectroscopic techniques. Electrochemical measurements showed addition of bentonite or phosphate mineral reduced the corrosiveness of H3PO4 polluted with S2− considerably. X-ray photoemission spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) showed these inhibitors did not incorporate into the passive film of the material and, therefore, did not induce any change in capacitance of the passive film. Results suggested the inhibiting effect stemmed from avoiding the adsorption of S2− ions on the nickel surface.Peer Reviewe

Effet des traitements thermiques sur la résistance à la corrosion en HCl molaire de l'alliage amorphe Fe-B-Si-C. Efficacité inhibitrice du diorthoaminophénoldisulfane (DOAPD)

Les thermogrammes d'analyse thermique différentielle (A.T.D.) et les spectres de diffraction de rayons X ont été réalisés avec l'alliage amorphe Fe-B-Si-C avant et après recuit. La résistance à la corrosion en HCl molaire de l'alliage recuit et non recuit a été évaluée et comparée à celle du fer cristallin αFe. L'efficacité inhibitrice de diorthoaminophenoldisulfane (DOAPD) a été calculée dans tous les cas

A new corrosion inhibitor for Cu60-Zn brass in 3% NaCl solution

The efficiency of 3-phenyl-1,2,4-triazole-5-thione (PTS) as brass corrosion inhibitor in 3% NaCl solution was investigated using electrochemical impedance spectroscopy gravimetric and potentiodynamic measurements. The surface were analyzed by scanning electron microscopy and energy dispersive x-ray analysis (EDAX).The results showed that the examined compound act as a mixed inhibitor. PTS inhibiting efficiency increased by augmenting its concentrations and by lengthening the testing time. At 1 mM concentration the polarization of the anodic branch at high current density is believed to be due to the resistance of the formed film. The EDAX analysis showed that the protection of brass by PTS is due to the formation of chemisorbed monolayer film. It growth involved precipitation of Cu and Zn ions may be as highly insoluble Cu-ZnPTS complexes at the solid/liquid interface