Novel Ce thin-film covering on a Mn–Ce–P conversion coating for excellent corrosion resistance of LZ91 alloy

Mg alloys exhibit an excellent strength-to-weight ratio, have favorable electromagnetic shielding characteristics, and are biocompatible. Alloying Mg with Li can further reduce weight and enhance ductility along with toughness. Unfortunately, MgLi alloys are susceptible to corrosion, which can poten...

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Bibliographic Details
Published inSurface & coatings technology Vol. 484; p. 130784
Main Authors Aktug, Salim Levent, Jian, Shun-Yi, Chang, Chin-Jou, Liu, Yu-Cheng
Format Journal Article
LanguageEnglish
Published Elsevier B.V 30.05.2024
Subjects
Conversion coating
Corrosion resistance
Electrochemical impedance spectroscopy
Magnesium alloy
Microstructure
Salt spray test
Corrosion resistance
Salt spray test
Microstructure
Conversion coating
Magnesium alloy
Electrochemical impedance spectroscopy
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Summary:Mg alloys exhibit an excellent strength-to-weight ratio, have favorable electromagnetic shielding characteristics, and are biocompatible. Alloying Mg with Li can further reduce weight and enhance ductility along with toughness. Unfortunately, MgLi alloys are susceptible to corrosion, which can potentially lead to disastrous material failure. Hence, developing an effective and environmentally friendly anticorrosion treatment is essential. In our previous study, we found that a Mn–Ce–P conversion coating can protect the LZ91 Mg alloy surface from corrosion and enhance its stability in an acidic bath. However, the Mn–Ce–P conversion coating may have cracks and lower corrosion resistance than the MnCe coating; hence, a fast, compact, environmentally friendly, room-temperature Ce conversion coating method was developed for use as a two-step treatment for the Mn–Ce–P conversion coating. Specimens were produced, and the coating microstructures were observed through SEM and TEM; the composition was then analyzed with EDS and X-ray photoelectron spectroscopy. EIS and a salt spray test were performed to quantify corrosion resistance. The two-step coating greatly improved the corrosion resistance; following 72 h exposure to salt spray test, the corrosion area was smaller than 3 %. •A novel two-step conversion coating for excellent corrosion resistance on LZ91.•A compact Ce-based coating was fabricated on Mn–Ce–P coated LZ91.•The composite coating reduced the corroded area to 3 % after 72 h SST.•The composite coating has excellent adhesion with a rating of 5B.•The mechanism via Mn–Ce–P/Ce-based composite coating was proposed.
ISSN:0257-8972
1879-3347
DOI:10.1016/j.surfcoat.2024.130784