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Atmospheric corrosion of the MgAl alloy AM50 in rheocast and high pressure diecast conditions - Influence of Microstructure, CO2 and NaCl

Mehrdad Shahabi-Navid (Institutionen för kemi- och bioteknik, Oorganisk miljökemi)
Göteborg : Chalmers University of Technology, 2014. - 51 s.
[Licentiatavhandling]

The NaCl-induced atmospheric corrosion of the high pressure diecast (HPDC) MgAl alloy AM50 was investigated. Commercially pure (CP) Mg was used as the reference. Two levels of salt; i.e. 14 and 70µg/cm² NaCl were added to the polished samples before exposure. Specimens without salt were used as references. The exposures were carried out in air with 0 or 400ppm CO2 to investigate the influence of carbon dioxide on corrosion. Gravimetric data was collected after the exposures. Alloy AM50 corroded less severely compared to CP Mg. The passive film and the corrosion products were analyzed qualitatively by means of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Brucite was the main corrosion product in the absence of CO2. Three magnesium hydroxy carbonates were the major corrosion products in the presence of CO2. The microstructure of the as-cast material and the morphology of the corroded samples were studied by scanning electron microscopy (SEM) and the elemental composition of the different alloy constituents was investigated by energy dispersive X-ray spectroscopy (EDX). The corrosion behavior of HPDC AM50 was compared to that of the alloy manufactured by rheocasting (RC). The average corrosion rate was lower for the RC alloy compared to the HPDC form in the presence of CO2. Larger primary α-Mg grains were observed in the RC alloy. Also, the RC alloy had a larger area fraction of β particles compared to the HPDC alloy.

Nyckelord: MgAl alloy, High pressure diecast, Rheocast, Atmospheric corrosion, SEM, XRD, XPS



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Denna post skapades 2014-06-02. Senast ändrad 2014-09-02.
CPL Pubid: 198729

 

Institutioner (Chalmers)

Institutionen för kemi- och bioteknik, Oorganisk miljökemi (2005-2014)

Ämnesområden

Materialvetenskap
Korrosionsteknik
Materialteknik

Chalmers infrastruktur

Relaterade publikationer

Inkluderade delarbeten:


NaCl-Induced Atmospheric Corrosion of the MgAl Alloy AM50-The Influence of CO2


NaCl-induced atmospheric corrosion of MgAl alloy AM50 in semi-solid cast and high pressure die cast form; relation between alloy microstructure and corrosion


Examination

Datum: 2014-02-28
Tid: 13:15
Lokal: Room 10:an, Chemistry building (forskarhus I), Kemigården 4
Opponent: Dr. Dan Persson

Ingår i serie

Licentiatuppsatser vid Institutionen för kemi- och bioteknik, Chalmers tekniska högskola 1652-943X