Effect of Acid Pickling Pretreatment on the Properties of Cerium Conversion Coating on AZ31 Magnesium Alloy

Su, Hsiang-Yu; Li, W. J.; Lin, Chao-Sung

doi:10.1149/2.jes113585

Cited by 36 publications

(16 citation statements)

References 40 publications

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“…3f shows the selected area electron diffraction (SAED) pattern of the compact layer, which consisted of diffraction rings resulting from Ce (IV) oxide (CeO 2 ). 19,41 The thickness of the Ce oxide on the Ce-coated 0.5 wt% HF-and 11 wt% HF-pretreated AZ91D was around 160 nm and 40 nm, respectively. Moreover, craters were occasionally observed on the Ce-coated 0.5 wt% HF-pretreated coupon, as marked by the arrow in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…17 Su et al demonstrated that comparing to the HCl pretreatment, the pretreatment in HF solution remarkably reduced the amounts of blisters and effectively enhanced the adhesion and corrosion resistance of the Ce conversion coating on the AZ31. 41 However, HF is one of the dangerous acids and potentially causes severe burns and systemic toxicity. 42 As a consequence, efforts were made in this study looking for a substitute for HF solution.…”

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confidence: 99%

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Corrosion Resistance Studies of Cerium Conversion Coating with a Fluoride-Free Pretreatment on AZ91D Magnesium Alloy

Lee

Chen

Lin

2012

J. Electrochem. Soc.

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An alternative of toxic hydrofluoric acid (HF) commonly used in the pretreatment process of magnesium (Mg) alloys prior to the conversion coating treatment in a cerium (Ce) nitrate and hydrogen peroxide bath was systematically investigated in this study. Comparing with the HF-and HCl-pretreated samples, the corrosion film formed in the vanadate solution at pH 8 effectively retarded the reaction rate of the Ce conversion coating. As a result, the average size and population density of blisters on the Ce conversion coating were markedly reduced. Both the electrochemical impedance spectroscopy and salt spray test showed that the Ce conversion coating with improved corrosion resistance can be made on the AZ91D that was pretreated in the vanadate solution for 120 s. Consequently, the vanadate solution is a feasible alternative to the HF solution for the pretreatment of the AZ91D prior to the Ce conversion coating treatment.Due to their light weight, high specific strength and stiffness, magnesium (Mg) alloys have been widely used in electric appliances and as structural components. 1,2 However, poor corrosion resistance continues to be a challenge for the extensive applications of Mg alloys. Several surface modification treatments are continuously developed to increase the corrosion resistance of Mg alloys, including anodizing, 3-7 conversion coatings, 8-25 electroless nickel plating, electrodeposition of nickel 26 and physical vapor deposition of high purity magnesium. 27 The conversion coating treatment is known as an effective corrosion protection method with the advantage of low cost and easy operation, especially the chromate conversion process. However, hexavalent Cr is highly toxic. Therefore, chromate-free solutions have thus been developed and include phosphate, phosphate/permanganate, stannate, and rare-earth metal salt solutions. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Cerium (Ce) conversion coating treatments are recognized for a simple electrolyte composition, which is generally considered to be environmentally friendly. Hinton et al. investigated the Ce conversion coating on aluminum (Al) alloys in the mid 1980s. 28,29 Since then, many papers have been published and showed that the Ce conversion coatings can effectively inhibit the corrosion of Al alloys. [30][31][32][33][34][35][36][37][38][39][40] In the past decade, Ce conversion coating treatments were applied on Mg alloys. [15][16][17][18][19][20][21][22] Rudd et al. treated the pure Mg and WE43 Mg alloy in Ce, lanthanum, and praseodymium solutions and found a significant increase in corrosion resistance of Mg in a pH 8 buffer solution. 15 Dabala et al. found that the Ce-based conversion process improved the corrosion resistance of AZ63 Mg alloy in aqueous chloride media. Moreover, the structure of the Ce conversion coatings were found not to be homogeneous and large agglomerates were observed on a dual phase AZ63 Mg alloy. 16 Ardelean et al. designed a new conversion coating solution containing Ce, zirconium (Zr), and...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Corrosion Resistance Studies of Cerium Conversion Coating with a Fluoride-Free Pretreatment on AZ91D Magnesium Alloy

Lee

Chen

Lin

2012

J. Electrochem. Soc.

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“…Blisters are common defects on cerium conversion coatings. [14][15][16][17][18] Further immersion resulted in an increase in the amount and size of the blisters. Such blisters can lead to local detachment of the coating.…”

Section: Microstructural Characterizationmentioning

confidence: 99%

“…The two-layer coating was composed of an inner porous layer with Mg/Al oxide and hydroxide and an outer compact layer of cerium oxide (CeO 2 ). [14][15][16]18 Blisters are related to the breakdown of the CeO 2 layer due to hydrogen evolution. In this study, the cerium conversion coatings were conducted on AZ91 magnesium plates in cerium nitrate aqueous solution with H 2 O 2 .…”

Section: Introductionmentioning

confidence: 99%

Influence of Vanadate Additive on the Properties of Cerium Conversion Coatings on AZ91 Magnesium Alloys

Lin

2013

ECS Trans.

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The present study investigates the microstructure and corrosion resistance of the cerium conversion coating on AZ91 magnesium plates in the cerium nitrate/hydrogen peroxide aqueous solution with and without sodium metavanadate. The microstructure characterization shows that the conversion coating displays a twolayered structure, an inner porous layer and an outer compact layer. Moreover, the size and population density of blisters are significantly reduced with the addition of NaVO 3 to the solution. The corrosion resistance is improved due to the decrease in defects within the coating.

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“…[6][7][8][9][10][11][12] It is well known that pure CeO 2 is pale yellow probably due to Ce(IV) -O(-II) charge transfer. 13 Whereas, CeO 2 color is sensitive that depends on the oxygen deficiency.…”

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The Composition-Dependent Color Evolution of Anodic Electrodeposited Cerium Oxide Thin Film

Yang

et al. 2014

J. Electrochem. Soc.

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Cerium oxide thin films with various colors were deposited onto 316L stainless steel using anodic electrodeposition approach. The correlation between color, composition and deposition time has been established. Results show that the film color evolves from golden yellow (1.5 h), purple (3 h), blue (5 h), gray-green (7 h) and turns back to yellow (12 h) again, and all these colored films are stable in the ambient conditions. The film color is related to both the contents of Ce(III) and hydroxide species in the films. The relative content of Ce(III) increases from 21.19% to 27.57% with increasing the deposition time from 1.5 h to 7 h, and then decreases to 22.93% for the film deposited at 12 h. The content of hydroxide species shows the same variation trend as Ce(III) with the deposition time.

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Effect of Acid Pickling Pretreatment on the Properties of Cerium Conversion Coating on AZ31 Magnesium Alloy

Cited by 36 publications

References 40 publications

Corrosion Resistance Studies of Cerium Conversion Coating with a Fluoride-Free Pretreatment on AZ91D Magnesium Alloy

Corrosion Resistance Studies of Cerium Conversion Coating with a Fluoride-Free Pretreatment on AZ91D Magnesium Alloy

Influence of Vanadate Additive on the Properties of Cerium Conversion Coatings on AZ91 Magnesium Alloys

The Composition-Dependent Color Evolution of Anodic Electrodeposited Cerium Oxide Thin Film

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