Research progress on preparation of phosphating film on magnesium


	alloys surface

Abstract

Abstract:

Phosphating is an important technological process for enhancing corrosion resistance of magnesium alloys. The

preparation of phosphating films takes the interface of the alloy/solution as place, coupling multiple physical,

chemical, and electrochemical processes. Firstly, this paper commences with the kinetics of phosphating to summarize the recent research of preparations of phosphating film on magnesium alloys surface and divides the phosphating process into three consecutive sub-processes: the electrochemical corrosion of the substrate, the reaction

and diffusion of ions at the alloy/solution interface, and the heterogeneous crystallization of the phosphating film.

Secondly, in chronological order, the role of synthesis parameters in phosphating regulation is analyzed to clarify

the influence of various factors on the phosphating of magnesium alloys. It is concluded that the self-coupling of

multiple factors such as temperature, substrate treatment methods, pH, etc., and the multiple cross-couplings with

the three phosphating sub-processes are the difficulties in understanding the formation mechanism of the phosphating film. Finally, the research direction on the preparation of phosphating films on the surface of magnesium

alloys are prospected.

Key words:

phosphating, magnesium alloys, dynamics, mechanism

CLC Number:

TB304

TONG Xiaoqiang , WANG Ruijue, , JIN Shenglong.

Research progress on preparation of phosphating film on magnesium

alloys surface

[J]. Journal of Civil Aviation University of China, 2025, 43(3): 86-96.

References )

	[1]
	RAHIMI S K, POTREKAR R, DUTTA N K, et al． Anticorrosive interfa－
	cial coatings for metallic substrates[J]． Surface Innovations, 2013, 1(2):
	112-137．
	[2]
	SANKARA NARAYANAN T S N． Phosphate conversion coatings[M]//
	SAJI V S, SANKARA NARAYANAN T S N, CHEN X B, et al． Conver－
	sion Coatings for Magnesium and Its Alloys． Cham: Springer Interna－
	tional Publishing, 2022: 73-112．
	[3]
	HAFEEZ M A, FAROOQ A, ZANG A, et al． Phosphate chemical con－
	version coatings for magnesium alloys: a review[J]． Journal of Coatings
	Technology and Research, 2020, 17(4): 827-849．
	[4]
	LIU B, ZHANG X, XIAO G Y, et al． Phosphate chemical conversion
	coatings on metallic substrates for biomedical application: a review[J]．
	Materials Science & Engineering C-Materials for Biological Applica－
	tions, 2015, 47: 97-104．
	[5]
	CHEN X B, YANG H Y, ABBOTT T B, et al． Corrosion protection of
	magnesium and its alloys by metal phosphate conversion coatings[J]．
	Surface Engineering, 2014, 30(12): 871-879．
	[6]
	VAN PHUONG N, LEE K, CHANG D, et al． Zinc phosphate conversion
	coatings on magnesium alloys: a review[J]． Metals and Materials Inter－
	national, 2013, 19(2): 273-281．
	[7]
	MACHU W. Phosphate coating and its scientific fundamental[J]. Mettawirtschaft, 1943, 22: 481-487.

	[8]


	SONG Y W, SHAN D Y, CHEN R S, et al． Formation mechanism of phosphate conversion film on Mg-8.8Li alloy [J]． Corrosion Science, 2009,


	51(1): 62-69．


	[9]


	KOUISNI L, AZZI M, ZERTOUBI M, et al． Phosphate coatings on mag－


	nesium alloy AM60 part 1: study of the formation and the growth of zinc


	phosphate films[J]． Surface and Coatings Technology, 2004, 185(1): 58-


	67．


	[10] JEFFREY BINNS W, ZARGARZADAH F, DEHNAVI V, et al． Physical


	and electrochemical evidence for the role of a Mg hydride species in Mg


	alloy corrosion[J]． CORROSION, 2019, 75(1): 58-68．


	[11] KARST J, STERL F, LINNENBANK H, et al． Watching in situ the hy－


	drogen diffusion dynamics in magnesium on the nanoscale[C]//2021 Conference on Lasers and Electro-Optics(CLEO), San Jose, CA, USA． IEEE,


	2021: 1-2．


	[12] ZHAO M, LI J G, HE G P, et al． Nano Al2O3 /phosphate composite con－


	version coating formed on magnesium alloy for enhancing corrosion resistance[J]． Journal of the Electrochemical Society, 2013, 160(11): C553-


	C559．


	[13] ZHOU P, YU B X, HOU Y J, et al． Revisiting the cracking of chemical


	conversion coating on magnesium alloys[J]． Corrosion Science, 2021, 178:


	109069．


	[14] SONG Y W, XU Z B, DONG K H, et al． Investigation of microcracks on


	conversion film of AZ80 Mg alloy[J]． Surface Engineering, 2019, 35(6):


	527-535．


	[15] DUAN G Q, YANG L X, LIAO S J, et al． Designing for the chemical conversion coating with high corrosion resistance and low electrical con－


	tact resistance on AZ91D magnesium alloy[J]． Corrosion Science, 2018,


	135: 197-206．


	[16] DU H Y, REN X J, PAN D, et al． Effect of phosphating solution pH val－


	ue on the formation of phosphate conversion coatings for corrosion be－


	haviors on AZ91D[J]． Advanced Composites and Hybrid Materials, 2021,


	4(2): 401-414．


	[17] NIU J L, YUAN G Y, LIAO Y, et al． Enhanced biocorrosion resistance


	and biocompatibility of degradable Mg -Nd -Zn -Zr alloy by brushite


	coating[J]． Materials Science & Engineering C-Materials for Biological


	Applications, 2013, 33(8): 4833-4841．


	[18] CHEN X B, BIRBILIS N, ABBOTT T B． Effect of Ca2+ and PO4


	3-


	levels


	on the formation of calcium phosphate conversion coatings on die-cast


	magnesium alloy AZ91D[J]． Corrosion Science, 2012, 55: 226-232．


	[19] CHEN X B, BIRBILIS N, ABBOTT T B． A simple route towards a hydroxyapatite-Mg(OH)2 conversion coating for magnesium[J]． Corrosion Science, 2011, 53(6): 2263-2268．


	[20] YANG J, ZHANG P, SU L, et al． The one-step preparation and corro－


	sion resistance of a Ca-Mn-Zn ternary phosphate conversion coating on


	magnesium alloy AZ91D[J]． Anti-Corrosion Methods and Materials, 2022,


	69(4): 341-350．


	[21] NGUYEN T L, CHENG T C, YANG J Y, et al. A zinc-manganese composite phosphate conversion coating for corrosion protection of AZ91D


	alloy: growth and characteristics[J]. Journal of Materials Research and


	Technology, 2022, 19: 2965-2980.


	[22] ZAI W, ZHANG X R, SU Y C, et al． Comparison of corrosion resistance


	and biocompatibility of magnesium phosphate (MgP), zinc phosphate


	(ZnP) and calcium phosphate (CaP) conversion coatings on Mg alloy[J]．


	Surface and Coatings Technology, 2020, 397: 125919．


	[23] ZAI W, SU Y C, MAN H C, et al． Effect of pH value and preparation


	temperature on the formation of magnesium phosphate conversion coat－


	ings on AZ31 magnesium alloy[J]． Applied Surface Science, 2019, 492:


	314-327．


	[24] LI G Y, LIAN J S, NIU L Y, et al． Growth of zinc phosphate coatings on


	AZ91D magnesium alloy[J]． Surface and Coatings Technology, 2006, 201


	(3/4): 1814-1820．


	[25] SANKARA NARAYANAN T S N． Surface pretreatment by phosphate


	conversion coatings: a review[J]． Reviews on Advanced Materials Sci－


	ence, 2005, 9(2): 130-177．


	[26] NIU L Y, JIANG Z H, LI G Y, et al． A study and application of zinc


	phosphate coating on AZ91D magnesium alloy[J]． Surface and Coatings


	Technology, 2006, 200(9): 3021-3026．


	[27] CUI X J, LIU C H, YANG R S, et al． Duplex-layered manganese phos－


	phate conversion coating on AZ31 Mg alloy and its initial formation mechanism[J]．Corrosion Science, 2013, 76: 474-485．


	[28] JIA X J, SONG J F, QU X R, et al． Effect of scratch on corrosion resis－


	tance of calcium phosphate conversion coated AZ80 magnesium alloy[J]．


	Transactions of Nonferrous Metals Society of China, 2022, 32(1): 147-


	161．


	[29] JIA X J, SONG J F, XIAO B Q, et al． Influence of indentation size on the


	corrosion behaviour of a phosphate conversion coated AZ80 magnesium


	alloy[J]． Journal of Materials Research and Technology, 2021, 14: 1739-


	1753．


	[30] YOU M Y, ECHEVERRY-RENDON M, ZHANG L, et al． Effects of


	composition and hierarchical structures of calcium phosphate coating on


	the corrosion resistance and osteoblast compatibility of Mg alloys[J]． Ma－


	terials Science & Engineering C-Materials for Biological Applications,


	2021, 120: 111734．


	[31] MAURYA R, SIDDIQUI A R, BALANI K. An environment -friendly


	phosphate chemical conversion coating on novel Mg-9Li-7Al-1Sn and


	Mg-9Li-5Al-3Sn-1Zn alloys with remarkable corrosion protection [J].


	Applied Surface Science, 2018, 443: 429-440.


	[32] ZHANG L S, JIANG Y, ZAI W, et al． Fabrication of superhydrophobic


	calcium phosphate coating on Mg-Zn-Ca alloy and its corrosion resis－


	tance[J]． Journal of Materials Engineering and Performance, 2017, 26


	(12): 6117-6129．


	[33] SU Y C, GUO Y T, HUANG Z L, et al． Preparation and corrosion behav－


	iors of calcium phosphate conversion coating on magnesium alloy[J]．Surface and Coatings Technology, 2016, 307: 99-108．


	[34] ZHANG C Y, ZENG R C, LIU C L, et al． Comparison of calcium phos－


	phate coatings on Mg-Al and Mg-Ca alloys and their corrosion behavior


	in Hank′ssolution[J]． Surface and Coatings Technology, 2010, 204(21/22):


	3636-3640．


	[35] LI T, WANG S F, LIU H T, et al． Improved corrosion resistance of Mg


	alloy by a green phosphating: insights into pre-activation, temperature,


	and growth mechanism[J]． Journal of Materials Science, 2021, 56(1): 828-


	843．


	[36] LI T, LENG Z J, WANG S F, et al． Comparison of the effects of pre-ac－


	tivators on morphology and corrosion resistance of phosphate conversion

	coating on magnesium alloy[J]． Journal of Magnesium and Alloys, 2022,


	10(12): 3485-3494．


	[37] XU Z B, SONG Y W, DONG K H, et al． Effects of second phases on the


	formation mechanism and corrosion resistance of phosphate conversion


	film on AZ80 Mg alloy[J]． Anti-Corrosion Methods and Materials, 2018,


	65(6): 587-593．


	[38] LU X P, CHEN Y Y, ZHANG C Y, et al． Formation mechanism and cor－


	rosion performance of phosphate conversion coatings on AZ91 and MgGd-Y-Zr alloy[J]． Journal of the Electrochemical Society, 2018, 165(10):


	C601-C607．


	[39] DONG K H, SONG Y W, SHAN D Y, et al． An optimization of pretreat－


	ment for the phosphate conversion film on WE43 magnesium alloy [J]．


	Materials and Corrosion, 2018, 69(4): 481-491．


	[40] YUAN J, YUAN R, WANG J H, et al． Fabrication and corrosion resis－


	tance of phosphate/ZnO multilayer protective coating on magnesium al－


	loy[J]． Surface and Coatings Technology, 2018, 352: 74-83．


	[41] ZHOU P, YANG L X, HOU Y J, et al． Grain refinement promotes the


	formation of phosphate conversion coating on Mg alloy AZ91D with high


	corrosion resistance and low electrical contact resistance[J]． Corrosion


	Communications, 2021, 1: 47-57．


	[42] ZENG R C, ZHANG F, LAN Z D, et al． Corrosion resistance of calciummodified zinc phosphate conversion coatings on magnesium-aluminium


	alloys[J]．Corrosion Science, 2014, 88: 452-459．


	[43] VAN PHUONG N, MOON S, CHANG D, et al． Effect of microstructure


	on the zinc phosphate conversion coatings on magnesium alloy AZ91[J]．


	Applied Surface Science, 2013, 264: 70-78．


	[44] ZHANG C Y, LIU B, YU B X, et al． Influence of surface pretreatment on


	phosphate conversion coating on AZ91 Mg alloy[J]． Surface and Coatings


	Technology, 2019, 359: 414-425．


	[45] SONG G L, XU Z Q． The surface, microstructure and corrosion of mag－


	nesium alloy AZ31 sheet[J]． Electrochimica Acta, 2010, 55(13): 4148-


	4161．


	[46] LIU H L, TONG Z P, YANG Y, et al． Preparation of phosphate conver－


	sion coating on laser surface textured surface to improve corrosion per－


	formance of magnesium alloy[J]． Journal of Alloys and Compounds, 2021,


	865: 158701．


	[47] LIU H L, GU J Y, TONG Z P, et al. Improving stress corrosion cracking


	resistance of AZ31 magnesium alloy in Hanks′ solution via phosphate


	conversion with laser shock peening pretreatment[J]. Materials Today


	Communications, 2022, 31: 103678.


	[48] LIU H L, TONG Z P, GU J Y, et al． Effect of laser surface texturing


	depth and pattern on the bond strength and corrosion performance of


	phosphate conversion coating on magnesium alloy[J]． Optics Laser Technology, 2022, 153: 108164．


	[49] BRUNELLI K, DABALA M, CALLIARI I, et al． Effect of HCl pre-treatment on corrosion resistance of cerium-based conversion coatings on


	magnesium and magnesium alloys[J]． Corrosion Science, 2005, 47(4):


	989-1000．


	[50] HUANG Y H, LEE Y L, LIN C S． Acid pickling pretreatment and stan－


	nate conversion coating treatment of AZ91D magnesium alloy[J]． Journal


	of the Electrochemical Society, 2011, 158(9): C310．


	[51] YANG H Y, CHEN X B, GUO X W, et al． Coating pretreatment for Mg


	alloy AZ91D[J]． Applied Surface Science, 2012, 258(14): 5472-5481．


	[52] LIAO S J, YU B X, ZHANG B, et al． Chemically depleting the noble im－


	purities from AZ91-T4 magnesium alloy: a new and efficient pretreat－


	ment method to improve the corrosion resistance of phosphate conver－


	sion coatings[J]． Corrosion Science, 2021, 191: 109725．


	[53] VAN PHUONG N, LEE K H, CHANG D, et al． Effects of Zn2+ concentration and pH on the zinc phosphate conversion coatings on AZ31 magnesium alloy[J]． Corrosion Science, 2013, 74: 314-322．


	[54] LI G, LIAN J, NIU L, et al． Influence of pH of phosphating bath on the


	zinc phosphate coating on AZ91D magnesium alloy[J]． Advanced Engineering Materials, 2006, 8(1/2): 123-127．


	[55] CHEN X B, ZHOU X, ABBOTT T B, et al． Double-layered manganese


	phosphate conversion coating on magnesium alloy AZ91D: insights into


	coating formation, growth and corrosion resistance[J]． Surface and Coatings Technology, 2013, 217: 147-155．


	[56] NIU L Y, LIN J X, LI Y, et al． Improvement of anticorrosion and adhe－


	sion to magnesium alloy by phosphate coating formed at room tempera－


	ture[J]． Transactions of Nonferrous Metals Society of China, 2010, 20(7):


	1356-1360．


	[57] 胡宗球, 华英杰, 朱立红, 等．无机化学(上册)[M]．北京: 科学出版社,


	2013: 36-37.


	[58] LIU D, LI Y Y, ZHOU Y, et al． The preparation, characterization and


	formation mechanism of a calcium phosphate conversion coating on magnesium alloy AZ91D[J]． Materials, 2018, 11(6): 908．


	[59] BELL R P． The rates of simple acid-base reactions[J]． Quarterly Re－


	views, Chemical Society, 1959, 13(3): 169-182．


	[60] HYMAN E S． A study of the rate of chelation of magnesium by CDTA


	and EDTA in the ATP (Na+ + K+
)	-ATPase system[J]． Biochimica et Bio－


	physica Acta (BBA) - Biomembranes, 1980, 600(2): 553-570．


	[61] ZENG R C, LAN Z D, KONG L H, et al． Characterization of calciummodified zinc phosphate conversion coatings and their influences on


	corrosion resistance of AZ31 alloy[J]． Surface and Coatings Technology,


	2011, 205(11): 3347-3355．


	[62] CHEN X B, BIRBILIS N, ABBOTT T B． Review of corrosion-resistant


	conversion coatings for magnesium and its alloys[J]． Corrosion, 2011, 67


	(3): 035005-1-035005-16．


	[63] ZALUDIN M A F, ZAHID JAMAL Z A, DERMAN M N, et al． Fabrica－


	tion of calcium phosphate coating on pure magnesium substrate via sim－


	ple chemical conversion coating: surface properties and corrosion per－


	formance evaluations[J]． Journal of Materials Research and Technology,


	2019, 8(1): 981-987．


	[64] ZHANG C Y, LIAO S J, YU B X, et al． Ratio of total acidity to pH value


	of coating bath: a new strategy towards phosphate conversion coatings


	with optimized corrosion resistance for magnesium alloys[J]． Corrosion


	Science, 2019, 150: 279-295．


	[65] FOULADI M, AMADEH A． Effect of phosphating time and temperature


	on microstructure and corrosion behavior of magnesium phosphate coat－


	ing[J]． Electrochimica Acta, 2013, 106: 1-12．


	[66] KIBALCZYC W, ZIELENKIEWICZ A． Calorimetric investigations of


	calcium phosphate precipitation[J]． Journal of Crystal Growth, 1987, 82


	(4): 733-736．


	[67] 仝晓强, 王瑞珏, 金胜龙. 一种 Hureaulite 磷酸锰转化膜的制备方法:


	CN116288302A[P]. 2023-06-23


	[68] LI Q, XU S Q, HU J Y, et al． The effects to the structure and electroche-

	mical behavior of zinc phosphate conversion coatings with ethanolamine


	on magnesium alloy AZ91D[J]． Electrochimica Acta, 2010, 55(3): 887-


	894．


	[69] MULLIN J W． Crystallization[M]． 4th ed. Amsterdam: Elsevier, 2001:


	289-314．


	[70] 马冬威, 史秋月, 袁国民, 等．工艺参数对 38MnVS 钢锰系磷化膜表


	面形貌和耐蚀性的影响[J]．表面技术, 2017, 46(8): 221-225．


	[71] AGHAMOHAMMADI H, RABIEE S M, HOSSEINIPOUR S J, et al. Ef－


	fect of microstructure and texture of Az31 magnesium alloy substrate on


	nucleation and growth of biomimetic calcium phosphate coating[J]. Journal of Materials Research and Technology, 2023, 27: 5154-5164.


	[72] HOU Y J, ZHOU P, YU B X, et al． The dual role of Mg2+ in the conver－


	sion bath during the treatment of magnesium alloys: the completing ef－


	fect between heterogeneous nucleation and crystal growth[J]． Electrochimica Acta, 2021, 388: 138568．


	[73] CUI L Y, WEI G B, ZENG R C, et al． Corrosion resistance of a novel


	SnO2-doped dicalcium phosphate coating on AZ31 magnesium alloy[J]．


	Bioactive Materials, 2018, 3(3): 245-249．


	[74] LOU G, JIA P, TENG X Y, et al． Nano ZnO-assisted formation of zinc


	phosphate conversion coating for improving corrosion protection of


	AZ91D magnesium alloy[J]． Materials Research Express, 2019, 6(8):


	086405．


	[75] SU Y C, SU Y C, ZAI W, et al． In vitro degradation behaviors of man－


	ganese-calcium phosphate coatings on an Mg-Ca-Zn alloy[J]． Scanning,


	2018, 2018: 6268579．


	[76] ZHOU P, GUO H, LI M M, et al． Preheating Mg alloy before the phos－


	phate conversion treatment: the enhanced crystal precipitation kinetics


	associated with the elevated temperature at reaction fronts[J]． Electrochimica Acta, 2022, 431: 141153．


	[77] AMINI R, SARABI A A． The corrosion properties of phosphate coating


	on AZ31 magnesium alloy: the effect of sodium dodecyl sulfate (SDS) as


	an eco-friendly accelerating agent[J]． Applied Surface Science, 2011,


	257(16): 7134-7139．


	[78] ZHOU W Q, SHAN D Y, HAN E H, et al． Structure and formation mechanism of phosphate conversion coating on die-cast AZ91D magnesium


	alloy[J]． Corrosion Science, 2008, 50(2): 329-337．


	[79] TANGUY P, ALL魪LY C, DRAGOE D, et al． On the effect of multiphase


	microstructure of ZnAlMg substrate on the Ti -based activation and


	phosphate conversion coating distribution[J]． Surface & Coatings Technology, 2019, 369: 165-174．


	[80] ZHAO H, CAI S, DING Z T, et al． A simple method for the preparation


	of magnesium phosphate conversion coatings on a AZ31 magnesium al－


	loy with improved corrosion resistance[J]． RSC Advances, 2015, 5(31):


	24586-24590．


	[81] 廖赏举．界面反应控制的镁合金磷酸盐转化膜研究[D]．合肥: 中国


	科学技术大学, 2021．


	[82] 仝晓强, 王瑞珏, 罗顺伟．一种金属表面化学转化膜的制备方法:


	CN113186527A[P]． 2021-07-30．

Research progress on preparation of phosphating film on magnesium

alloys surface

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