Ceria based coatings deposited on magnesium alloys.

Mg alloy	Type of coating	Coating thickness	Most relevant result	Corrosion parameters estimated via potentiodynamic polarization test	Biological evaluation	Ref.	Year
AZ91D	CeO2- and ascorbic acid (Hasc)- based coatings	∼5 μm	The incorporation of ascorbic acid into the Ce-based coating improved its anticorrosive properties. The presence of insoluble cerium precipitates and the formation of insoluble chelates are associated with improved corrosion resistance	E corr a	Not reported	88	2018
				AZ91D: −1.501 V
				RCe-HAsc: −0.952 V
				I corr b
				AZ91D: 0.105 mA cm−2
				RCe-HAsc: 5.4 × 10−3 mA cm−2
				I corr of the coating samples was found to be one order of magnitude lower than that of the uncoated substrate
AZ31	CeO2 coating	1.1 μm and 5.3 μm	CeO2 coatings showed a good protective ability after immersion for 96 h in a 1 NaCl solution, which indicates their good corrosion resistance and durability	Not reported	Not reported	90	2018
AZ91D	Cerium and cerium molybdenum coating	Not reported	Cerium and cerium molybdenum coats can effectively improve the corrosion resistance of the alloy	E corr a	Not reported	91	2018
				AZ91D: − 1.501 V
				Ce-coat: − 1.095 V
				Ce–Mo-coat: − 0.785 V
				I corr b
				AZ91D: 0.105 mA cm−2
				Ce-coat: 1.5 × 10−2 mA cm−2
				Ce–Mo-coat: 9 × 10−3 mA cm−2
Pure Mg	CeO2/ZnO coating	∼16 μm	The corrosion rate of the pure Mg drastically reduced from 10.8 to 0.81 mpy due to composite coating. During corrosion, passive layers of Ce(OH)2, Mg(OH)2, and zinc oxy-chloride were formed. The layers exhibited improved adhesion and higher corrosion resistance	I corr b	Not reported	92	2019
				Pure mg: 1.2 × 10−7 mA cm−2
				CeO2/ZnO: 9 × 10−9 mA cm−2
				I corr of the CeO2/ZnO composite coating decreased by 3 × 10−5 μAcm−2 when compared to that of pure Mg
AZ31	Tetraethyl-orthosilicate (TEOS) and glycidoxypropyl-triethoxysilane (GPTMS) coating doped with Ce(NO3)3	Between 0.9 and 3.3 μm	Ceria in sol–gel coatings were found to deposit on the active sites of the Mg alloy providing corrosion protection	E corr a	Not reported	85	2020
				AZ31: −1.47 V
				TEOS + GPTMS + Ce(NO3)3: −1.46 V
				I corr b
				AZ31: 6.60 × 10−3 mA cm−2
				TEOS + GPTMS + Ce(NO3)3: 6.85 × 10−5 mA cm−2
				The coatings synthesized with Ce(NO3)3 exhibited a reduction in Icorr of about two orders of magnitude when compared to the uncoated AZ31 alloy
Pure Mg	Multi-layer coating of calcium, cerium, hyaluronic acid (HA), and carboxymethyl cellulose (CMC)	19.4 ± 0.09 μm	The morphology, chemical structure, and scratch tests revealed that the samples treated with Ce were the most effective in terms of self-healing and corrosion resistance. The films containing HA and CMC acted as a pathway for the diffusion of Ce ions into the film, protecting the Mg substrate and oxide film and maximizing self-healing	Not reported	In vitro assays using osteoblast cells showed no toxicity in ceria-based coatings. Furthermore, Ce-coated substrates exhibited good cellular expression	86	2020
					In vivo implantation tests in rat tibiae showed stable growth of bone marrow and osteoblasts in coatings containing ce
LZ91	Permanganate/cerium coating	0.66 μm	Permanganate/cerium coatings were found to be more anticorrosive than chromate coatings	E corr a	Not reported	93	2020
				LZ91: −1.64 V
				LZ91/Permanganate/cerium coating
				−1.53 V
				I corr b
				LZ91: 1.85 × 10−2 mA cm−2
				LZ91/Permanganate/cerium coating: 1.02 × 10−3 mA cm−2
AZ31	CeO2 NPs in a hybrid epoxy–silane coating	10.4 ± 1.9 μm	Coating with 325 ppm of CeO2 improved corrosion protection and aided in the healing of the pitting corrosion of the AZ31 alloy	Not reported	Not reported	32	2021
WE43	Ce(DEHP)3 in a hybrid epoxy–silane coating	3.90 ± 0.54 μm	The barrier properties of the coating were improved. The presence of Ce(DEHP)3 improved the corrosion resistance. The self-healing effect of Ce(DEHP)3 was found to be pH-dependent	Not reported	Not reported	78	2021
AZ91	Alumina and cerium oxide sol–gel coating	Not reported	The corrosion resistance of the Mg alloy improves with increasing cerium content in the coating (up to 10% CeO2 content)	Not reported	No reported	94	2021
Mg-4 wt%Y	Cerium-based conversion coating (CeCC)	1.30 μm	CeCC coating retard the corrosion process of Mg alloy and decrease the corrosion rate (∼50–70% compared to bare alloy)	E corr a	Not reported	95	2021
				Mg-4 wt%Y: −1.60 V
				Mg-4 wt%Y –CeCC-30 s: −1.64 V
				I corr b
				Mg-4 wt%Y: 5.88 10−2 mA cm−2
				Mg-4 wt%Y–CeCC: 1.69 10−2 mA cm−2
AZ31	Zinc–cerium, LDH/oxide	Not reported	The layered double hydroxides (LDH) were composed of the Zn2+ cations and the complex of the Ce3+ and Ce4+. The coating showed adequate self-healing capacity and corrosion resistance	E corr a	Not reported	96	2021
				AZ31: −1.57 V
				AZ31/Zn–Ce LDH/oxide: −1.26 V
				I corr b
				AZ31: 1.2 × 10−2 mA cm2
				AZ31/Zn–Ce LDH/oxide Icorr: 9.8 × 10−5 mA cm2
AZ61	CeO2-based composite	1.4 μm	The composite coating used is composed of the cerium conversion coating, a dense CeO2 layer, a porous CeO2 nanorods, and stearic absorbing layers. The coatings improve the corrosion resistance of Mg alloy and showed superhydrophobic properties	E corr a	Not reported	97	2021
				AZ61: 1548.0 V
				AZ61/Ceria-based: −1433.5 V
				I corr b
				AZ61: 35.3 × 10−2 mA cm−2
				AZ61/ceria-based: 2.0 × 10−4 mA cm−2
AZ31	Multi-layer coating composed of MAO/phytic acid (PA)/CeO2	5 μm	Self-healing coatings can release cerium ions to the active sites to form a new layer and inhibit further substrate corrosion	E corr a	Not reported	98	2022
				AZ31: −1.51 V
				AZ31/MAO/PA/Ce: −1.62 V
				I corr b
				AZ31: 7.9 × 10−2 mA cm−2
				AZ31/MAO/PA/Ce: 1.24 × 10−4 mA cm−2
				I corr of the MAO/PA/CeO2 coating decreased by two orders of magnitude
AZ31	Zinc–cerium LDH coating	Between 6.1 and 24.1 μm	The LDH coating composed of Zn and Ce cations on the Mg alloy has self-healing and corrosion protection properties	E corr a	Not reported	99	2022
				AZ31: −1.57 V
				Zn–Ce LDH-coat: −1.198 V
				I corr b
				AZ31: 1.08 mA cm−2
				Zn–Ce LDH-coat: 1.29 × 10−5 mA cm−2
AZ91D	Duplex cerium-epoxy coating	Not reported	The presence of cerium in the coating provides a corrosion inhibition effect on Mg alloy	E corr a	Not reported	100	2022
				AZ91D: −1.420 V
				Duplex coat: −0.706 V
				I corr b
				AZ91D: 0.108 mA cm−2
				Duplex coat: 2.763 × 10−6 mA cm−2
WE43C-T5	Duplex cerium-hybrid coating	2.06 μm	The addition of cerium to the coating increases the corrosion resistance of Mg alloy. Cerium exhibits self-healing properties by migrating to defect sites	E corr a	Not reported	101	2022
				WE43C-T5: −1.66 V
				Duplex coat: −1.59 V
				I corr b
				WE43C-T5: 0.109 mA cm−2
				Duplex coat: 6 × 10−3 mA cm−2
AZ31	Calcium–cerium based LDH	22 μm	The developed coating acts as a corrosion inhibitor and exhibits self-healing properties. The release of ce, Ca and Mg ions in the corrosive medium of the Mg surface and tries to cure the defects by forming some compounds as corrosion products. This process delays the corrosion process of the metal	E corr a	Not reported	102	2022
				AZ31: −1.61 V
				AZ31/Ca–Ce based LDH: −1.19 V
				I corr b
				AZ31: 54.72 mA cm−2
				AZ31/Ca–Ce based LDH: 0.058 mA cm−2

^a E _corr: Corrosion potential.

^b I _corr: Corrosion density.