ESTUDO ELETROQUÍMICO E DA CORROSÃO DO AÇO ASTM 285 GRAU C, NAS REGIÕES DE SOLDA E DA ZONA TERMICAMENTE AFETADA, EM SOLUÇÕES DE LICOR BRANCO, UTILIZADO EM DIGESTORES DA INDÚSTRIA DE PAPEL E CELULOSE, E SEUS PRINCIPAIS COMPONENTES

• Autor(a) principal: D’avila, Ariel Leandro
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UEPG
• Texto Completo: http://tede2.uepg.br/jspui/handle/prefix/1477
• topic: aço ASTM 285 Grau C; corrosão; filmes passivados; licor branco; papel e celulose; ASTM A285 Grade C; corrosion; passivated films; white liquor; pulp and paper industry; CNPQ::ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA

This work aims to study the electrochemical steel ASTM A285 Grade C and the same welded with coated electrode AWS E 7018 in the solution of industrial white liquor used in pulp and paper industry by the Kraft method. Samples were withdrawn by electroerosion into three regions: the base metal (BM), the heat affected zone (HAZ) and at the weld metal (WM). Corrosion rates of the three metal regions were determined in 8°C, 16°C, 24°C, 35°C, 42°C, 50°C and 60°C temperature. The values of corrosion rates were compared with the BM, ZTA and WM corrosion rates in electrolytic solutions of the main chemical components of the industrial white liquor in the same temperature range. These solutions were 0,1 mol/L of Na2SO4; 2.276 mol/L of NaOH; 0.126 mol/L of Na2S; 0.128 mol/L of Na2CO3 and simulated white liquor composed of the above solutions with the same molar concentrations. The BM to 24°C, industrial white liquor aerated presented corrosion rate of 0.022 mm/year, 0.045 mm/year for the HAZ and 0.032 mm/year for the WM. It was observed that the HAZ corrosion rates were higher than BM and WM in all solutions studied. Lower corrosion rates were in Na2CO3, followed by NaOH, Na2S, simulated white liquor and finally with the highest corrosion rates in white liquor industry. All solutions are presented alkaline, except sodium sulfate, and it was observed that the three regions are passivated when compared to a reference solution of 0.1 mol/L Na2SO4, and aerated with a pH between 6.0 to 6.5. This passivation film are complex chemical composition due to the presence in solution of OH- HS- ion. From the corrosion potentials of BM in each solution and the pH values it was found that the BM region is passivated according iron Pourbaix diagram in water. Chronoamperometry and voltammetric studies showed that these passivation films that promote greater protection against corrosion, they are solubilized in NaOH solution, simulated white liquor and industrial white liquor when submitted to anodic polarization in potential near at +2.0 V versus saturated calomel electrode. In Na2S and Na2CO3 solution was observed the formation of thick deposits on the surface of BM and when analyzed by EDS was observed the presence of phases such as oxides, sulfides and possibly iron carbonate.