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

Scaling platinum‐catalyzed hydrogen dissociation on corrugated surfaces

We determine absolute reactivities for dissociation at low coordinated Pt sites. Two curved Pt(111) single-crystal surfaces allow us to probe either straight or highly kinked step edges with molecules impinging at a low impact energy. A model extracts the average reactivity of inner and outer kink atoms, which is compared to the reactivity of straight A- and B-type steps. Local surface coordination numbers do not adequately capture reactivity trends for H(2)dissociation. We utilize the increase of reactivity with step density to determine the area over which a step causes increased dissociation. This step-type specific reactive area extends beyond the step edge onto the (111) terrace. It defines the reaction cross-section for H(2)dissociation at the step, bypassing assumptions about contributions of individual types of surface atoms. Our results stress the non-local nature of H(2)interaction with a surface and provide insight into reactivity differences for nearly identical step sites.Catalysis and Surface Chemistr

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

A study of step defects on NiAl(110) using a curved single crystal surface

Catalysis and Surface Chemistr

Adsorption of Fuchsin Basic on Copper in Citric Acid

The adsorption of Fuchsin Basic (FB) on copper surfaces in citric acid solutions whose concentrations ranged from 0.001 to 0.1 M was investigated using gravimetric measurements. The concentrations of FB studied ranged from 1 × 10 −5 to 1 × 10 −1 M with adsorption experiments being conducted at temperatures from 298 K to 328 K. The adsorption mechanism is discussed in terms of the applicability of the conventional Frumkin, Bockris–Swinkels and Kastening–Holleck isotherms, amongst others. The best fit was obtained using the Frumkin isotherm model. A thermodynamic/kinetic model of adsorption was also fitted