Preparations and Corrosion Protection Investigations of Diethylene Triamine Penta(Methylene Phosphonic Acid)-Zn²⁺ Conversion Coatings on Cold Rolled Steel Substrates

Authors

Wei HE, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China;
Ru YAN, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China;
Ying-qi WANG, State Key Laboratory of Separation Membranes and Membrane Processes/Separation Membrane Science and Technology International Joint Research Centre, Tianjin Polytechnic University, Tianjin 300387, China;School of Materials Science and Engineering, Tianjin Polytechnic University, Tianjin 300387, China;
Xiang GAO, Key Laboratory of Marine Environmental Corrosion and Bio-fouling, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;
Hou-yi MA, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China;Follow

Corresponding Author

Hou-yi MA(hyma@sdu.edu.cn)

Abstract

Novel diethylene triamine penta(methylene phosphonic acid) (DTPMPA)-zinc ion (Zn²⁺) conversion coatings with uniform blue color and excellent corrosion protection were directly formed on the cold rolled steel (CRS) substrates by immersing a CRS plate into the film-forming solutions containing the appropriate concentrations of DTPMPA and Zn²⁺ ion at the proper pH. In this paper, surface morphologies and elemental compositions of DTPMPA-Zn²⁺ conversion coatings were characterized by SEM and EDS, respectivey. The surface functional groups, chemical constituents and binding modes to the substrates were investigated by means of FTIR and XPS methods. The influences of DTPMPA concentrations and pH values on the corrosion protection properties of the DTPMPA-Zn²⁺ conversion coatings were studied using electrochemical impedance spectroscopy (EIS) and polarization measurements. The results revealed that DTPMPA reacted with Zn²⁺ ions, forming the DTPMPA-Zn²⁺ chelate under the coexistence condition of both substances. Moreover, the chelate would be deposited onto the CRS substrate through the cross-linking of Zn²⁺ ions and form three-dimensional DTPMPA-Zn²⁺ thin films with uniform blue color and thickness. This kind of conversion coating exhibited the best corrosion resistance performance with the protection efficiency of 91.6% when the concentrations of DTPMPA and Zn²⁺ ion were 0.2wt% and 0.044wt%, respectively, in the film-forming solutions at pH = 3.0.

Graphical Abstract

Keywords

DTPMPA, chemical conversion coating, chelation, corrosion protection, pH, zinc ion

DOI Link

https://doi.org/10.13208/j.electrochem.170622

Publication Date

2018-04-28

Online Available Date

2017-10-16

Revised Date

2017-09-12

Received Date

2017-06-22

Recommended Citation

Wei HE, Ru YAN, Ying-qi WANG, Xiang GAO, Hou-yi MA. Preparations and Corrosion Protection Investigations of Diethylene Triamine Penta(Methylene Phosphonic Acid)-Zn²⁺ Conversion Coatings on Cold Rolled Steel Substrates[J]. Journal of Electrochemistry, 2018 , 24(2): 111-121.
DOI: 10.13208/j.electrochem.170622
Available at: https://jelectrochem.xmu.edu.cn/journal/vol24/iss2/2