Publicação

The negative-difference effect during the localized corrosion of magnesium and of the AZ91HP alloy

Detalhes bibliográficos
Resumo:	Galvanostatic tests with pure magnesium and with the AZ91HP alloy were performed in NaCl solutions, and the volume of hydrogen evolved during the tests was measured. In order to examine the negative-difference effect, a concept was developed to separate the hydrogen evolution (H.E.) on the passive surface and the H.E. inside the pits. An analysis of the volumetric data showed that the current density of H.E. inside the pits is much higher for Mg than for the AZ91HP alloy. With the assumption, that the ratio between the hydrogen reduction rate and the rate of the anodic metal dissolution, expressed by the factor k, does not change with the polarization, a k value of ca. 0.5 for pure Mg was found, while for the AZ91HP alloy this value was only ca. 0.3.
Autores principais:	Weber,Cristina R.
Outros Autores:	Knörnschild,Gerhard; Dick,Luís F. P.
Assunto:	magnesium localized corrosion AZ91HP alloy negative-difference effect
Ano:	2003
País:	Brasil
Tipo de documento:	artigo
Tipo de acesso:	acesso aberto
Instituição associada:	IBICT
Idioma:	inglês
Origem:	Oasisbr

Descrição
Resumo:	Galvanostatic tests with pure magnesium and with the AZ91HP alloy were performed in NaCl solutions, and the volume of hydrogen evolved during the tests was measured. In order to examine the negative-difference effect, a concept was developed to separate the hydrogen evolution (H.E.) on the passive surface and the H.E. inside the pits. An analysis of the volumetric data showed that the current density of H.E. inside the pits is much higher for Mg than for the AZ91HP alloy. With the assumption, that the ratio between the hydrogen reduction rate and the rate of the anodic metal dissolution, expressed by the factor k, does not change with the polarization, a k value of ca. 0.5 for pure Mg was found, while for the AZ91HP alloy this value was only ca. 0.3.

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