Corresponding Author

Xin-sheng ZHANG(xszhang@ecust.edu.cn)


Trivalent chromium ion (Cr3+) is used for electrodeposition due to its low toxicity. Electrodeposition in ionic liquids can greatly solve for hydrogen evolution problem. However,as a widely used Cr(III) precursor, chromium chloride hydrate (CrCl3·6H2O), still contains water. In the presence of water, Cr3+ will form a complex coordination structure with water molecules ([Cr(H2O)6]3+), which is a stable octahedral structure and is difficult to be directly reduced to chromium metal. Therefore, coordination agents should be added into the bath. In this work, the effect of 18-Crown-6 additive on chromium electrodeposition was investigated in CrCl3/[BMIM]HSO4/H2O plating solution. The UV-Vis spectra showed that 18-Crown-6 formed a complex with Cr3+, destroyed the stable coordination structure formed by Cr3+ and water molecules, making a red shift in the maximum absorption wavelength. The cyclic voltammograms indicated that the electroreduction of Cr3+ occurred in a two-step process, namely, Cr3+ + e → Cr2+ and Cr2+ + 2e → Cr0. Both of the peak potential and initial reduction potential of Cr3+ had positive shifts by 220 mV after adding 18-Crown-6. The reason for this phenomenon was that when 18-Crown-6 was added to the plating solution, the stable structure of [Cr(H2O)6]3+ was destroyed, Cr3+ became more readily to be reduced, thereby, lowered the reduction potential of Cr3+. The EDS data showed that the chromium content in the coating was increased under the action of 18-Crown-6. The improvement indicated that 18-Crown-6 was beneficial to the chromium electrodeposition. The SEM characterizations indicated that the coating obtained in 18-Crown-6/CrCl3/[BMIM]HSO4/H2O plating solution had a larger particle size. Tafel curves suggested that the corrosion resistance of chromium coating was better than that of brass substrate. The optimized process in 18-Crown-6/CrCl3/[BMIM]HSO4/H2O plating solution could be proceeded at the temperature of 50 oC, pH of 3.5, current density of 1200 A·m-2, and plating time of 1.5 h. The thickness of the chrome plating reached 72.5 μm and the current efficiency was 42.3%.

Graphical Abstract


trivalent chromium, 1-butyl-3-methyl imidazole sulfate, 18-Crown-6, chromium electrodeposition, current efficiency

Publication Date


Online Available Date


Revised Date


Received Date



[1] Giovanardi R, Orlando G.Chromium electrodeposition from Cr(III) aqueous solutions[J]. Surface & Coatings Technology, 2011, 205(15): 3947-3955.

[2] Soragni E, Fontanesi C, Barani G, et al.Dynamic aspects of the electroreduction of chromic acid solutions[J]. Journal of Applied Electrochemistry, 2000, 30(9): 1069-1079.

[3] Lu C E, Pu N W, Hou K H, et al.The effect of formic acid concentration on the conductivity and corrosion resistance of chromium carbide coatings electroplated with trivalent chromium[J]. Applied Surface Science, 2013, 282: 544-551.

[4] de Lima-Neto P, da Silva G P, Correia A N. A comparative study of the physicochemical and electrochemical properties of Cr and Ni-W-P amorphous electrocoatings[J]. Electrochimica Acta, 2006, 51(23): 4928-4933.

[5] Zeng Z X, Sun Y L, Zhang J Y.The electrochemical reduction mechanism of trivalent chromium in the presence of formic acid[J]. Electrochemistry Communications, 2009, 11(2): 331-334.

[6] Abbott A P, Ryder K S, Konig U.Electrofinishing of metals using eutectic based ionic liquids[J]. Transactions of The Institute of Metal Finishing, 2008, 86(4): 196-204.

[7] Eugenio S, Rangel C M, Vilar R, et al.Electrochemical aspects of black chromium electrodeposition from 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid[J]. Electrochimica Acta, 2011, 56(28): 10347-10352.

[8] Saravanan G, Mohan S.Corrosion behavior of Cr electrodeposited from Cr(VI) and Cr(III)-baths using direct(DCD) and pulse electrodeposition(PED) techniques[J]. Corrosion Science, 2009, 51(1): 197-202.

[9] Del Pianta D, Frayret J, Gleyzes C, et al.Determination of the chromium(III) reduction mechanism during chromium electroplating[J]. Electrochimica Acta, 2018, 284: 234-241.

[10] Abbott A P, McKenzie K J,. Application of ionic liquids to the electrodeposition of metals[J]. Physical Chemistry Chemical Physics, 2006, 8(37): 4265-4279.

[11] Galiński M, Lewandowski A, Stępniak I.Ionic liquids as electrolytes[J]. Electrochimica Acta, 2006, 51(26): 5567-5580.

[12] Rao Zh, Feng K, Tang B B, et al.Surface decoration of amino-functionalized metal-organic framework/graphene oxide composite onto polydopamine-coated membrance substrate for highly efficient heavy metal removal[J]. ACS Applied Materials & Interfaces, 2017, 9(3): 2594-2605.

[13] Abbott A P, Capper G, Davies D L, et al.Electrodeposition of chromium black from ionic liquids[J]. Transactions of the IMF, 2004, 82(1/2): 14-17.

[14] He X K, Li C, Zhu Q Y, et al.Electrochemical mechanism of Cr(III) reduction for preparing crystalline chromium coatings based on 1-butyl-3-methylimidazolium hydrogen sulfate ionic liquid[J]. RSC Advances, 2014, 4(109): 64174-64182.

[15] Surviliené S, Nivinskiené O, Ĉešuniené A, et al.Effect of Cr(III) solution chemistry on electrodeposition of chromium[J]. Journal of Applied Electrochemistry, 2006, 36(6): 649-654.

[16] El-Sharif M, Mcdougall J, Chisholm C.Electrodeposition of thick chromium coatings from an environmentally acceptable chromium(III)-glycine complex[J]. Transactions of the IMF, 1999, 77(4): 139-144.

[17] Protsenko V, Gordiienko V, Butyrina T, et al.Hard chromium electrodeposition from a trivalent chromium bath containing water-soluble polymer[J]. Turkish Journal of Chemistry, 2014, 38(1): 50-55.

[18] Su N, Bradshow J S, Zhang X X, et al.Syntheses and metal ion complexation of novel 8-hydroxyquinoline-containingdizaz-18-crown-6 ligands and analogues[J]. Journal of Organic Chemistry, 1999, 64(24): 8855-8861.

[19] Tu C Q, Surowiec K, Bartsch R A.Novel calix[4]arenethiacrown ether for selective and efficient extraction of Ba(II), Pb(II), and Hg(II)[J]. Journal of Inclusion Phenomena and Macrocyclic Chemistry, 2007, 58(3/4): 361-366.

[20] Tsukube H, Shinoda S, Mizutani Y, et al. Enhanced Li+ ion-selective ionophoric properties of double armed diaza-l2-crown-4 derivatives[J]. Tetrahedron, 1997, 53(10): 3487-3496.

[21] Kim K S, Shin B K, Lee H.Physical and electrochemical properties of 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium iodide, and 1-butyl-3-methylimidazolium tetrafluoroborate[J]. Korean Journal of Chemical Engineering, 2004, 21(5): 1010-1014.

[22] He X K, Zhu Q Y, Hou B L, et al.Electrodeposition of nanocrystalline chromium coatings from 1-butyl-3-methy limidazolium-hydrogen sulfate ionic liquid[J]. Surface and Coatings Technology, 2015, 262: 148-153.

[23] Sun L Y, Brennecke J F.Characterization of imidazolium chloride ionic liquids plus trivalent chromium chloride for chromium electroplating[J]. Industrial & Engineering Chemistry Research, 2015, 54(17): 4879-4890.

[24] Survilien$\acute{e}$ S, Eugenio S, Vilar R.Chromium electrodeposition from[Bmim][BF4] ionic liquid[J]. Journal of Applied Electrochemistry, 2011, 41(1): 107-114.



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.