Corrosion behavior of Zn-TiO2 and Zn-ZnO Electrodeposited Coatings in 3.5% NaCl solution

Electrodeposition is a widely used method to protect metallic materials from corrosion. Electrodeposited coatings provide the metal substrate with both cathodic protection and a barrier effect. The corrosion resistance achieved with this type of zinc-electroplating process in increased by adding nanometric materials to the electrolytic bath. In the present research, coatings were obtained by electrodeposition of pure zinc, Zn-TiO2 and Zn-ZnO nanoparticles. The coatings were generated by immersion in a chloride acid bath applying a current density of 0.05 and 0.10 A/cm2 for 1 min and adding 2 g/l of TiO2 or ZnO nanoparticles. Corrosion behaviour was evaluated with potentiodynamic polarization curves and the electrochemical impedance spectroscopy (EIS) technique using a 3.5% NaCl test solution. After electrochemical testing, the coating surface morphology was analysed by scanning electron microscopy (SEM) and the atomic composition by energy dispersive X-ray spectroscopy (EDS). The electrodeposited coating thickness was measured using the ultrasound technique. The coating thickness was less than 2.5 μm and its corrosion resistance increased with the addition of nanoparticles

Effect of temperature on passive film formation of UNS N08031 Cr-Ni alloy in phosphoric acid contaminated with different aggressive anions

tThe influence of temperature and the effect of aggressive anions on the electrochemical behaviour of UNSN08031 stainless steel in a contaminated phosphoric acid solution were evaluated. Stabilisation of thepassive film was studied by potentiodynamic polarisation curves, potentiostatic tests, electrochemicalimpedance spectroscopy (EIS) measurements, Mott Schottky analysis and X-ray photoelectron spec-troscopy (XPS). The stability of the passive film was found to decrease as temperature increases. The filmformed on the stainless steel surface was a n-type semiconductor and the XPS spectrum revealed thepresence of fluoride ions.Authors express their gratitude to the Ministry of Education of Spain (MHE2011-00202) for its financial support during the stay at University of Manchester, to MAEC of Spain (PCI Mediterraneo C/8196/07, C/018046/08, D/023608/09 and D/030177/10) and to the Generalitat Valenciana (GV/2011/093) for the financial support. The authors would also like to acknowledge the support of the School of Materials at the University of Manchester for providing analytical and technical support for the study.Escrivá Cerdán, C.; Blasco Tamarit, ME.; García García, DM.; García Antón, J.; Akid, R.; Walton, J. (2013). Effect of temperature on passive film formation of UNS N08031 Cr-Ni alloy in phosphoric acid contaminated with different aggressive anions. Electrochimica Acta. 111:552-561. https://doi.org/10.1016/j.electacta.2013.08.040S55256111

Chemical Composition of the Copper/Benzotriazole Interface in the Presence of Acetic Acid Vapour at Low Humidities

Studies were made of the chemical composition of the copper products formed at 43, 58 and 78% relative humidity (RH) in contaminated (10-ppm acetic acid vapour) and uncontaminated environments in the presence and absence of the volatile corrosion inhibitor benzotriazole (BTA) for 7 d at 30°C. Such studies were conducted using X-ray photoelectron spectroscopy (XPS). General XPS spectra over a wide binding energy region showed C and O peaks in addition to those corresponding to the different copper compounds. Copper specimens exposed to acetic acid vapour in the presence of BTA also exhibited N emissions. The main compounds formed were cuprite (Cu 2 O), copper hydroxide [Cu(OH) 2 ], copper acetate and copper-benzotriazole (Cu-BTA) complexes

Precipitation mechanism of soluble phosphates in mortar

The penetration of three phosphate compounds in mortar bulk matrix, sodium monofluorophosphate (Na2FPO3) (MFP), disodium hydrogen phosphate (Na2HPO4) (DHP) and trisodium phosphate (Na3PO4) (TSP) has been evaluated using two water:cement ratios (0.5 and 0.6). The mortar samples were immersed in a 5% MFP, DHP or TSP solution for a period of 40 days. Microprobe line profile analysis for phosphorus (P) and fluorine (F) showed similar behaviour for the three soluble phosphates, which penetrated the mortar to a depth of more than 2 mm, below which the P and F contents dropped to almost zero. The stability of the phosphate ions vs. pH was calculated using thermodynamic data to obtain the following stability ranges: pH 2–4 for ion, pH 5−9 for ion, pH 3–6 for ion, pH 8–12 for ion, and pH above 11 for ion. The use of the MFP, DHP and TSP as corrosion inhibitors presents some limitations in the case of total or partial immersion

Low energy SIMS characterization of passive oxide films formed on a low-nickel stainless steel in alkaline media

Low-energy secondary ion mass spectrometry (SIMS) was used to study the oxide films formed on a low-nickel austenitic stainless steel (SS), potential replacement to conventional AISI 304 SS in reinforced concrete structures (RCS) that are subjected to aggressive environments. The effect of carbonation and the presence of chloride ions were studied. The oxide films formed a chemically gradated bi-layer structure with an outer layer predominately constituted by iron oxides and an inner layer enriched in chromium oxides. Chloride ions were not found in the oxide film but did have an effect on film structure and thickness