Crystallization of a chemical conversion layer that forms on AZ91D magnesium alloy in carbonic acid

Corrosion resistance of Mg–Al-LDH coating on magnesium alloy AZ31

“…1d. Jun-Yen Uan's research group [25,26] also reported that the Mg-Al-LDH produced by the in situ method possessed a porous outer layer and a dense inner layer as evidenced by TEM micrographs. C fp represents the capacitance of the outer layer of the LDH coating at the interface.…”

“…LDHs can be expressed by the general formula [M layer, and the anion A n− is located in the hydrated interlayer galleries [27]. Recently, extensive studies have focused on the potential applications of LDHs as coatings to protect metals such as magnesium alloys [26], aluminum alloys [28], and steel [29,30]. To date, two main methods have been developed for preparing LDH coatings.…”

“…Among these surface treatments, chemical conversion coatings have advantages, including lower cost and simplicity of operation [11]. Many types of chemical conversion coatings have been applied to magnesium alloys, including coatings containing chromate [12], phytic acid [13,14], phosphate [15,16], stannate [17,18], vanadium [19], stearic acid [20], dawsonite [3], or rare-earth elements such as cerium [21], lanthanum [22] or hydrotalcite [23][24][25][26]. Nevertheless, some of these conversion coatings, such as chromate-and vanadatebased coatings, present environmental hazards, and stannate is not applicable for practical use at this stage.…”

“…One is the in situ method, and the other is the two-step method, in which the LDH power precursor is first synthesized by the coprecipitation method and then the coating is obtained using a certain process. Lin [25,26,31] adopted the in situ method to fabricate Mg, Al-hydrotalcite conversion films on AZ91 alloys in aqueous HCO 3 − / CO 3 2− medium and demonstrated that the resulting films exhibit good corrosion resistance. Chen [23,24,32] also applied the in situ method, preparing Mg-Al hydrotalcite conversion films on AZ31 alloys.…”

Corrosion Resistance of the Superhydrophobic Mg(OH)2/Mg-Al Layered Double Hydroxide Coatings on Magnesium Alloys

“…Recently, the LDHs have caused great interest as promising alternative conversion coatings for Mg alloys [10][11][12][13][14][15]. LDHs can be represented by the general formula [M 2+ 1´x M 3+ x (OH) 2 ] x+ (A) n´x /2¨m H 2 O, where the cations M 2+ and M 3+ occupy the octahedral holes in a brucite-like layer and the anion A n´i s located in the hydrated interlayer galleries [16].…”