Estudo da permeação do hidrogênio durante a eletrodeposição do zinco em diferentes banhos sobre o aço 1020

Abstract

This work aims to study some solutions used in zinc plating to minimize the generation and permeation of atomic hydrogen on steel in order to prevent metal embrittlement problems. This study was performed using cyclic voltammetry, determination of thickness, hydrogen permeation, and physical characterization by scanning electron microscopy (SEM).The solutions for Zn electrodeposition were: 1)0.1 mol L-1 ZnSO4 + 0.2 mol L-1 KCl,2) Bath 1 + 0.2 mol L-1 Na3Cit, 3) Bath 1 + 0.2 mol L-1 Na3Cit + 0.2 mol L-1 H3BO3, 4) Bath 1 + 0.2 mol L-1 H3BO3, 5) 0.01 mol L-1 ZnSO4, 0.2 mol L-1 H3BO3, 0.2 mol L-1 Na3Cit, 0.2 mol L-1 KCl e 6) Bath 1 + H3BO3 0.2 mol L-1 + hexametiltetramina 0.1 mol L-1. Permeation measurements were performed using a dual-compartment cell similar to Devanathan-Stachurski applying controlled current 7 mA cm-2. The presence of citrate in the baths 2, 3 had great influence on the formation of the electrodeposited zinc deposit and voltammogram profile due to the formation of complexes with the species in solution.The film that showed lower thickness was obtained by the bath 5 due to lower zinc concentration in solution. The lowest thickness of the coating obtained by the bath 5 facilitates the hydrogen input, increasing its concentration. The addition of the inhibitor hexametiltetramina the bath 6, influenced the formation of the Zn coating presenting denditrica morphology, with lower generation and hydrogen permeation obtained with respect to other baths.