Tecnologia em Metalurgia, Materiais e Mineração
https://tecnologiammm.com.br/article/doi/10.4322/tmm.2012.042
Tecnologia em Metalurgia, Materiais e Mineração
Artigo Original

INVESTIGAÇÃO DE CAMADA DE CONVERSÃO À BASE DE CROMO TRIVALENTE APLICADA SOBRE AÇO ELETROGALVANIZADO

INVESTIGATION OF TRIVALENT CHROMIUM-BASED CONVERSION COATINGS ON ELECTROGALVANISED STEEL

Tomachuk, Célia Regina; Santos, Alessandra Setúbal; Queiroz, Fernanda Martins

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Resumo

O processo de passivação do aço eletrozincado é muito importante, especialmente, como meio de proteção contra a corrosão, e a espessura da camada obtida pode incrementar ainda mais tal proteção. Existe no mercado tratamento de conversão à base de sais de cromo trivalente com camada espessa, no entanto, são operados a 60°C. Com o intuito de atender à demanda dos mercados nacional e internacional, que almejam processos com baixo consumo de energia, eletrólito com baixo teor de sais de cromo trivalente e ambientalmente amigáveis, este trabalho apresenta o desenvolvimento de um processo com somente 20% de sais de cromo trivalente no banho e com aplicação em temperatura ambiente. Os ensaios de resistência à corrosão foram realizados utilizando a técnica de espectroscopia de impedância eletroquímica em solução de cloreto e ensaios acelerados em câmara de névoa salina. A associação desses ensaios fornece uma avaliação mais completa do comportamento frente à corrosão da camada de conversão obtida. Os resultados obtidos com relação à aparência, brilho, homogeneidade, espessura de camada e resistência à corrosão são similares aos apresentados pelo produto contendo cromo trivalente existente no mercado e ao tratamento de conversão à base de sais de cromo hexavalente.

Palavras-chave

Corrosão, Aço eletrozincado, Cromo trivalente

Abstract

The passivation process of electrogavanised steel is very important, especially for improving of the corrosion protection and the thickness of the layer obtained can further enhance such protection. In the market exists Cr(III)‑based thick layers passivation, however, are operated around 60°C. In order to attend market demands a new process with only 20% of the chromium content is developed, which operates at room temperature. The corrosion behavior was investigated through electrochemical impedance spectroscopy technique in chloride solution and accelerated tests in salt spray chamber. The combination of these tests provides a more complete assessment of the behavior against corrosion of layer passivation obtained. The results with respect to appearance, brightness, uniformity, layer thickness and corrosion resistance are similar to those presented by Cr(III) based passivation existing market and Cr(VI) based conversion treatment.

Keywords

Corrosion, Electrogalvanised steel, Trivalent chromium

Referências

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