Effect of Phosphomolybdate Content Regulation on Low-temperature Curing Waterborne Chromium-free Zinc-aluminum Coating and Its Passivation Behavior

AN Xiaoyun; LI Qingpeng; LIU Jiaxing; LUAN Junhan; YANG Hongqinag; LIU Yan

doi:10.16490/j.cnki.issn.1001-3660.2025.22.007

PDF(42653 KB)

Surface Technology ›› 2025, Vol. 54 ›› Issue (22) : 77-89. DOI: 10.16490/j.cnki.issn.1001-3660.2025.22.007

Effect of Phosphomolybdate Content Regulation on Low-temperature Curing Waterborne Chromium-free Zinc-aluminum Coating and Its Passivation Behavior

AN Xiaoyun¹, LI Qingpeng^1*, LIU Jiaxing¹, LUAN Junhan¹, YANG Hongqinag², LIU Yan³

Author information +

History +

Abstract

As an anode passivator instead of chromium anhydride, phosphomolybdate can exert excellent passivation ability in zinc-aluminum coatings. In order to explore the optimal content of phosphomolybdenum acid in the low-temperature curing system with 3-(2,3 epoxy propoxy) propy ltriethoxy silane (A-1871) as the film-forming material, the stability of the hydrolysate and zinc-aluminum coating, the micromorphology and composition of the coating and the corrosion resistance of the coating were characterized by storage stability, neutral salt spray test, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electrochemical polarization test, electrochemical impedance test and X-ray photoelectron spectroscopy (XPS). The experimental results showed that the content of phosphomolybdate (1.0%-3.0%) had no significant effect on the storage stability of the hydrolysate and zinc-aluminum coatings. The color of the silane hydrolysate would darken with the extension of storage time and the increase of phosphomolybdic acid content, but there was no gel and delamination. After 180 days of storage, there was no abnormal phenomenon such as gel, agglomeration and deterioration. When the phosphomolybdate content was 2.5%, only white rust appeared after 168 h salt spray test, but no red rust appeared. SEM showed that the coating before salt spray was dense and flat, and tightly bonded to the substrate. The surface flatness of the coating after salt spray disappeared, but the cross-section test showed that the coating was still tightly integrated with the substrate, without faults and gaps, and the cross-sectional morphology was not much different from that before salt spray. The electrochemical polarization test showed that the corrosion current density of the zinc-aluminum coating-2.5 was 9.9316×10^-8 A/cm², which was reduced by one to two orders of magnitude compared with other coatings, and the polarization resistance reached 125 350 Ω·cm². Moreover, the corrosion potential of the polarization curve of the corroded coating was negatively shifted by nearly 300 mV compared with that of the Q235 carbon steel matrix, which proved that it still had cathodic protection ability. The electrochemical impedance test showed that the zinc-aluminum coating-2.5 showed a large impedance modulus, and the R_ct after fitting was as high as 17 929 Ω·cm², which showed better corrosion resistance compared with other coatings. The immersion monitoring experiment of zinc-aluminum coating-2.5 found that on the fifth day, the capacitive arc radius was more than 30 000 Ω·cm², and the fitting R_ct reached 46 982 Ω·cm², which was due to the joint action of zinc-aluminum powder, phosphomolybdic acid and silane to play the sacrificial anode role of zinc-aluminum powder, and the zinc-aluminum powder was passivated by phosphomolybdate powder, and the insoluble water-insoluble substances were accumulated on the surface of the coating after the zinc-aluminum powder was corroded, so as to enhance the physical shielding ability, so that the coating at this time was the most dense and had the best anti-corrosion performance. XPS confirmed that phosphorus and molybdenum were present in the coating in the form of Zn₃(PO₄)₂, AlPO₄, MoO₃, ZnMoO₄ and Al₂(MoO₄)3, forming a composite protective layer with both physical barrier and chemical passivation functions. This experiment proves that phosphomolybdenum acid can effectively improve the corrosion resistance of zinc-aluminum coating, and has a certain continuous passivation ability, which provides theoretical support for the design of environmentally friendly passivator.

Key words

phosphomolybdate / aqueous chromium-free zinc-aluminum coating / passivator / passivation / anticorrosion / electrochemistry

Cite this article

EndNote

Ris (Procite)

Bibtex

Download Citations

AN Xiaoyun, LI Qingpeng, LIU Jiaxing, LUAN Junhan, YANG Hongqinag, LIU Yan. Effect of Phosphomolybdate Content Regulation on Low-temperature Curing Waterborne Chromium-free Zinc-aluminum Coating and Its Passivation Behavior[J]. Surface Technology. 2025, 54(22): 77-89 https://doi.org/10.16490/j.cnki.issn.1001-3660.2025.22.007

References

[1] 于升学. 达克罗处理技术的现状与发展[J]. 电镀与涂饰, 2001, 20(3): 54-57.
YU S X.Current Status and Development of Dacromet Technology[J]. Electroplating & Finishing, 2001, 20(3): 54-57.
[2] 巴彬彬, 谭勇, 安成强. 达克罗技术的现状及发展[J]. 辽宁化工, 2020, 49(1): 83-85.
BA B B, TAN Y, AN C Q.Development and Present Situation of Dacromet Technology[J]. Liaoning Chemical Industry, 2020, 49(1): 83-85.
[3] 张俊敏, 张宏, 文自伟, 等. 达克罗技术的现状与发展方向[J]. 表面技术, 2004, 33(6): 11-12.
ZHANG J M, ZHANG H, WEN Z W, et al.Status and Development Direction of Dacromet Technology[J]. Surface Technology, 2004, 33(6): 11-12.
[4] 朱福, 辛宇, 田伟, 等. 无铬锌铝涂料研究现状与发展趋势[J]. 涂料工业, 2023, 53(7): 83-88.
ZHU F, XIN Y, TIAN W, et al.Research Status and Development Trend of Chromium-Free Zinc-Aluminum Coatings[J]. Paint & Coatings Industry, 2023, 53(7): 83-88.
[5] 王崇蕊, 李杰庆, 尹鸿鹍, 等. 无铬达克罗涂层技术的研究进展[J]. 当代化工研究, 2022(22): 13-15.
WANG C R, LI J Q, YIN H K, et al.Development of the Chromium-Free Dacromet Coating Technology Based on Bibliometric[J]. Modern Chemical Research, 2022(22): 13-15.
[6] 魏小昕, 冯立新, 沈杰. 无铬达克罗涂层的研究进展[J]. 现代涂料与涂装, 2014, 17(2): 34-36.
WEI X X, FENG L X, SHEN J.Research Progress of the Non-Chromium Dacromet Technology Coating[J]. Modern Paint & Finishing, 2014, 17(2): 34-36.
[7] 赵晓莹. 水性无铬达克罗涂料配方研究及其涂层性能测试[D]. 北京: 北京化工大学, 2019.
ZHAO X Y.Study on formulation of water-based chrome-free dacromet coating and performance test of its coating[D]. Beijing: Beijing University of Chemical Technology, 2019.
[8] 李敏, 李庆鹏, 阎磊, 等. 钒酸钠型无铬达克罗涂层的制备与性能[J]. 电镀与涂饰, 2022, 41(24): 1735-1744.
LI M, LI Q P, YAN L, et al.Preparation and Properties of Chromium-Free Dacromet Coating Based on Sodium Vanadate[J]. Electroplating & Finishing, 2022, 41(24): 1735-1744.
[9] 李新波, 曾鹏, 谢光荣, 等. 稀土镧盐对水性锌铝涂层的钝化作用[J]. 材料保护, 2011, 44(10): 19-22.
LI X B, ZENG P, XIE G R, et al.Effect of Rare Earth Lanthanum Salt on Passivation of Water-Borne Zn-Al Coating[J]. Materials Protection, 2011, 44(10): 19-22.
[10] 张克冰. 无铬达克罗涂层的制备与性能研究[D]. 新乡: 河南师范大学, 2017.
ZHANG K B.Study on the preparation and properties of chrome-free ddcromet coating[D]. Xinxiang: Henan Normal University, 2017.
[11] 石存秀, 曾鹏, 李国亮, 等. 稀土盐对水性锌铝合金涂层的微观结构与耐蚀性能的影响[J]. 电镀与涂饰, 2010, 29(6): 51-54.
SHI C X, ZENG P, LI G L, et al.Influence of Rare Earth Salt on the Microstructure and Corrosion Resistance of Water-Based Zinc-Aluminum Alloy Coating[J]. Electroplating & Finishing, 2010, 29(6): 51-54.
[12] 张好, 张潇华, 赵保钢, 等. 磷钼酸钠型无铬锌铝涂层的制备与性能研究[J]. 上海涂料, 2023, 61(5): 46-50.
ZHANG H, ZHANG X H, ZHAO B G, et al.Preparation and Performance Study of Chromium-Free Zn-Al Coating with Sodium Phosphomolybdate[J]. Shanghai Coatings, 2023, 61(5): 46-50.
[13] 李慧莹, 赵君文, 戴光泽, 等. 钼酸钠含量对无铬锌铝涂层性能的影响[J]. 材料导报, 2020, 34(2): 105-109.
LI H Y, ZHAO J W, DAI G Z, et al.Impact of Sodium Molybdate Content on Properties of Chromium-Free Zinc-Aluminum Coatings[J]. Materials Review, 2020, 34(2): 105-109.
[14] 安晓云, 李庆鹏, 栾钧涵, 等. 基于钝化剂调控对低温固化水性无铬锌铝涂层的性能研究[J]. 电镀与涂饰, 2025, 44(10): 121-130.
AN X Y, LI Q P, LUAN J H, et al.Performance Characterization of Low-Temperature-Curable Waterborne Chromium-Free Zinc-Aluminum Coating Based on Passivator Control[J]. Electroplating & Finishing, 2025, 44(10): 121-130.
[15] 乔珊. 酸性条件下钨钼还原特征研究[D]. 赣州: 江西理工大学, 2012.
QIAO S.Study on Reduction Characteristics of Tungsten and Molybdenum under Acidic Conditions. Ganzhou: Jiangxi University of Science and Technology, 2012.
[16] MATSUZAKI A, YAMAJI T, YAMASHITA M.Development of a New Organic Composite Coating for Enhancing Corrosion Resistance of 55% Al-Zn Alloy Coated Steel Sheet[J]. Surface and Coatings Technology, 2003, 169: 655-657.
[17] GU T Z, ZHANG P, GUO M X, et al.Corrosion Behavior of Zinc-Aluminum-Magnesium Coated Steel in Simulated Marine Atmosphere[J]. International Journal of Electrochemical Science, 2022, 17(5): 22054.
[18] CHANG C H, HUANG T C, PENG C W, et al.Novel Anticorrosion Coatings Prepared from Polyaniline/Graphene Composites[J]. Carbon, 2012, 50(14): 5044-5051.
[19] CHANG K C, HSU M H, LU H I, et al.Room-Temperature Cured Hydrophobic Epoxy/Graphene Composites as Corrosion Inhibitor for Cold-Rolled Steel[J]. Carbon, 2014, 66: 144-153.
[20] 李勃杭, 许凯欣, 孙文, 等. 改性氟化石墨烯增强氟树脂防腐蚀涂层的制备及性能[J]. 电镀与涂饰, 2022, 41(12): 868-876.
LI B H, XU K X, SUN W, et al.Preparation and Properties of Modified Fluorographene-Reinforced Anticorrosive Fluororesin Composite Coating[J]. Electroplating & Finishing, 2022, 41(12): 868-876.
[21] TIAN W L, MENG F D, LIU L, et al.Lifetime Prediction for Organic Coating under Alternating Hydrostatic Pressure by Artificial Neural Network[J]. Scientific Reports, 2017, 7: 40827.
[22] ZHOU Q X, WANG Y C.Comparisons of Clear Coating Degradation in NaCl Solution and Pure Water[J]. Progress in Organic Coatings, 2013, 76(11): 1674-1682.
[23] ZHANG K B, ZHANG M M, QIAO J F, et al.Enhancement of the Corrosion Resistance of Zinc-Aluminum-Chromium Coating with Cerium Nitrate[J]. Journal of Alloys and Compounds, 2017, 692: 460-464.
[24] 李耀辉, 廖宏儿, 耿铁, 等. 镁合金表面Mg-MOF-74/硅烷复合涂层的制备及耐蚀性[J]. 电镀与涂饰, 2022, 41(4): 245-250.
LI Y H, LIAO H E, GENG T, et al.Preparation and Corrosion Resistance of Mg-MOF-74/Silane Composite Coating on Magnesium Alloy Surface[J]. Electroplating & Finishing, 2022, 41(4): 245-250.
[25] 李庆鹏, 张登华, 杨宏强, 等. 无铬达克罗润滑防腐蚀封闭涂层的制备与性能研究[J]. 材料保护, 2021, 54(6): 1-6.
LI Q P, ZHANG D H, YANG H Q, et al.Study on the Preparation and Properties of Lubricating and Anti-Corrosion Seal Coating on the Chromium-Free Dacromet Coating Surface[J]. Materials Protection, 2021, 54(6): 1-6.
[26] 鲁俊, 梁英, 汤尚文, 等. 无铬达克罗涂料工艺及耐蚀性能研究[J]. 应用化工, 2011, 40(4): 612-613.
LU J, LIANG Y, TANG S W, et al.Study on Process and Corrosion Resistance of Chrome-Free Dacromet Coating[J]. Applied Chemical Industry, 2011, 40(4): 612-613.
[27] 李庆鹏, 刘利冉, 张亮, 等. 水性锌基涂镀涂层的制备及性能研究[J]. 材料导报, 2023, 37(11): 245-250.
LI Q P, LIU L R, ZHANG L, et al.Preparation and Properties of Water-Borne Zinc Coating[J]. Materials Reports, 2023, 37(11): 245-250.
[28] 刘建国, 金宁, 王淼, 等. 碳钢表面电镀锌镍/有机富铝复合涂层的制备与性能[J]. 电镀与精饰, 2024, 46(10): 56-66.
LIU J G, JIN N, WANG M, et al.Preparation and Properties of Electroplating Zinc-Nickel Alloy/Organic Aluminum-Rich Composite Coatings on Carbon Steel Surface[J]. Plating & Finishing, 2024, 46(10): 56-66.
[29] 李庆鹏, 安晓云, 蒋天成, 等. 硅烷和羟基化炭黑改性铝粉添加量对水性富铝环氧涂层性能的影响[J]. 电镀与涂饰, 2025, 44(6): 127-137.
LI Q P, AN X Y, JIANG T C, et al.Effect of the Dosage of Silane and Hydroxylated Carbon Black Modified Alu-minum Powder on Properties of Waterborne Aluminum-Rich Epoxy Coating[J]. Electroplating & Finishing, 2025, 44(6): 127-137.
[30] ZHAN W, QIAN X Z, GUI B Y, et al.Preparation and Corrosion Resistance of Titanium-Zirconium-Cerium Based Conversion Coating on 6061 Aluminum Alloy[J]. Materials and Corrosion, 2020, 71(3): 419-429.
[31] 李庆鹏, 许茜, 刘建国, 等. 水性无铬达克罗涂料的制备与性能研究[J]. 中国腐蚀与防护学报, 2016, 36(6): 559-565.
LI Q P, XU Q, LIU J G, et al.Preparation and Perfor-mance of Water-Based Chromiumfree Dacromet Coa-ting[J]. Journal of Chinese Society for Corrosion and Protection, 2016, 36(6): 559-565.
[32] MANSFELD F, KENDIG M W, TSAI S.Recording and Analysis of AC Impedance Data for Corrosion Studies II. Experimental Approach and Results[J]. Corrosion, 1982, 38(11): 570-580.
[33] 靳子昂, 朱丽娜, 刘明, 等. 热喷涂技术制备铝涂层及其在 3.5%NaCl 溶液中耐腐蚀性的研究现状[J]. 表面技术, 2019, 48(10): 220-229.
JIN Z A, ZHU L N, LIU M, et al.Research Status of Aluminum Coating Prepared by Thermal Spraying Tech-nology and Its Corrosion Resistance in 3.5% NaCl Solu-tion[J]. Surface Technology, 2019, 48(10): 220-229.