Influência da temperatura no processo eletroquímico de coloração por corrente pulsada nos aços inoxidáveis ABNT 304 e ABNT 430

• Ano de defesa: 2020
• Autor(a) principal: Jaqueline Lacerda da Silva
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; Brasil; ENG - DEPARTAMENTO DE ENGENHARIA QUÍMICA; Programa de Pós-Graduação em Engenharia Química; UFMG
• Palavras-chave em Português: Aço inoxidável colorido; Velocidade de coloração; Coloração eletroquímica; Filme de interferência; Engenharia química; Aço inoxidável; Eletroquímica
• Link de acesso: http://hdl.handle.net/1843/34568

The golden coloring of ABNT 304 and ABNT 430 stainless steels was performed using an electrochemical alternating pulsed current method developed at CETEC (PI 9703991-8), conducted at different temperatures. To understand the influence of temperature on the coloring time and the properties of the interference films deposited on substrates of austenitic and ferritic steels, the temperature of the coloring step was varied in the range of 25 ° C and 40 ° C. A higher coloring speed was found for ABNT 304 steel, in addition to an exponential reduction in coloring time with an increase in temperature for ABNT 304 and ABNT 430 steels, the latter being more influenced, reducing 36.6% the time by varying 15° C. It was possible to estimate the equations for specific growth rates of the films using the Arrhenius model. The chemical composition of the films was studied using XPS. The morphology of the films was analyzed by MO, MEV and MFA. The porous fraction of the films is in the range of 27 to 29%, with no relevant variation with the color temperature. The nanohardness of the film-substrate conjugate obtained by a nanoindentator coupled to the MFA decreased after the staining process, this reduction being more significant for the films on the ferritic substrate, possibly influenced by the larger pore size of these films. The nanomechanical parameters evaluated were independent of the temperature of the staining process. The wettability of the films in relation to water and oil increases after staining, with the most pronounced effect on ABNT 430 steel. The wettability of the films decreases with increasing coloring temperature. The amplification effect of the hydrophilic effect of the Wenzel and Cassie-Bexter models can be seen in the results of nanorugosity obtained by MFA, where the increase in surface roughness accompanies a reduction in the angle of contact with water. In the EIS test, the results showed a corrosion behavior of the colored samples slightly lower than the passive layer of the substrate, but maintaining the protective character of the interference film, with no significant differences between the substrates or temperature of coloring.