Estudo da influência dos depósitos de níquel e paládio sobre a densidade de corrente de oxidação do hidrogênio na liga API 5L X80.

Abstract

In this work, electrochemical permeation technique was applied to alloy API 5L X80 coated with nickel or palladium on the sample detection surface in three different thickness: 0,04; 0,08 and 0,12 um. For this, a two-compartment cell was used, both filled with 0,1 M NaOH, separated only by the metallic membrane, acting as working electrode. The metallic coating characterization was performed by cyclic voltammetry technique before and after the permeation step. Results obtained showed that alloy surface with Ni and Pd layers became more active after hydrogen permeation. Permeation results were expressed by following properties: diffusion coefficient, permeability and solubility. The average diffusion coefficient for samples with nickel deposit was (2,92 ± 1,06) m2/s, while for the samples with palladium deposit was (2,46 ± 0,61) m2/s. It was noticed that palladium shows a better electro catalytic performance besides more reproducible measurements and minor standard deviation. Interaction properties showed no dependence of coating thickness. Regarding nickel, these properties presented larger fluctuation and denoted some dependence for layer metallic coating.