Corrosion resistance and electrical contact resistance of a thin permanganate conversion coating on dual-phase LZ91 Mg–Li alloy
Journal
Journal of Materials Research and Technology
Journal Volume
11
Pages
1953-1968
Date Issued
2021
Author(s)
Abstract
A strongly acidic permanganate conversion coating solution containing 0.1 M KMnO4 at pH 1.5 adjusted with H2SO4 was employed for LZ91 magnesium-lithium alloy, realizing the formation of a thin protective coating with a low electrical contact resistance. The corrosion resistance of LZ91 alloy was markedly improved by the permanganate conversion coating, which consisted of MgO, MnO2, and Mg(OH)2. Coating formation proceeded on both the α-Mg phase and β-Li phase in this strongly acidic permanganate solution, achieving a full coverage of permanganate conversion coating within a short treatment time. When the immersion was prolonged to 30 s, cracks were present on the permanganate conversion coating, which deteriorated the corrosion resistance substantially. Moreover, the increase in the thickness of the coating elevated the electrical contact resistance. However, the relatively thin areas on the thin permanganate conversion coating became active sites where corrosion commenced. As a result, a thin uniform permanganate conversion coating is crucial for both enhanced corrosion resistance and reduced electrical contact resistance. ? 2021 The Author(s)
Subjects
Conversion coating
Electrical contact resistance
Magnesium
Polarization
Transmission electron microscopy
X-ray photon spectroscopy
Contact resistance
Corrosion resistant alloys
Corrosion resistant coatings
High resolution transmission electron microscopy
Lithium alloys
Magnesia
Magnesium alloys
Manganese alloys
Manganese oxide
Potash
Coating solution
Conversion coatings
Dual phase
Dual phasis
Magnesium-lithium alloys
Mg-Li alloy
Resistance contact
Thin protective coatings
X ray photon spectroscopy
Corrosion resistance
SDGs
Type
journal article