Melatonin as an Accelerating Agent for Phosphate Chemical Conversion Coatings on Mild Steel with Enhanced Corrosion Resistance

2020 ◽  
Vol 167 (10) ◽  
pp. 101505
Author(s):  
Yuqin Tian ◽  
Weijun Qiu ◽  
Yuhui Xie ◽  
Haowei Huang ◽  
Jin Hu ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Mild Steel ◽  
Chemical Conversion ◽  
Conversion Coatings

Zirconate Conversion Coatings on Al Alloy by Electrochemical Method

2012 ◽  
Vol 460 ◽  
pp. 86-89
Author(s):  
Qi Zhou ◽  
Hong Yan Liu ◽  
Xiu Lian Cheng ◽  
Guang Sen Zhang
Keyword(s):  
Corrosion Resistance ◽  
Paint Film ◽  
Chemical Conversion ◽  
First Grade ◽  
Conversion Coating ◽  
Complexing Agents ◽  
Complexing Agent ◽  
Al Alloy ◽  
Conversion Coatings ◽  
Electrochemical Conversion

Chromium-free conversion coatings were generated to replace chromate chemical process by electrolysis treatment LY12 aluminum alloy in zirconate solution. Film thickness, dropping test, the adhesion between aluminum and paint film were tested for single-factor experiments and orthogonal to seek better electrolysis process. The paint adhesion is the first grade for electrochemical conversion solution containing complexing agents, or it is the second grade without complexing agents. When DNS complexing agent is 2 ~ 5g/L, film corrosion resistance rises with the increasing content of complexing agent. If voltage is too low, corrosion resistance of conversion coating is poor; voltage is too high, the films form powders. Better formulations for zirconate conversion coating are: 5g/L DNS complexing agent, 10V voltage, treatment temperature is 40°C. Electrochemical conversion coating is thinner than chemical conversion, but the corrosion resistance is better because the electrochemical conversion coatings are smoother and compacter than the chemical conversion coating. The paint films on electrochemical conversion coating are smoother than the chemical one. Two kinds of conversion coatings have very good adhesion with paint film up to the first level. Electrochemical conversion coatings thickness is 2.5 μm, bubble time of NaOH-glycerine solution on them is up to 92s.

Surface Modification of Aluminum and Its Alloys Using Conversion Coatings

2019 ◽  
Author(s):  
L. Anicai ◽  
Teodor Visan
Keyword(s):  
Thin Films ◽  
Corrosion Resistance ◽  
Surface Modification ◽  
Rare Earth ◽  
Environmentally Friendly ◽  
Chemical Conversion ◽  
Rare Earth Compounds ◽  
Conversion Coatings ◽  
Transitional Metals ◽  
And Performance

This article presents some information related to the chemical conversion procedures applied onto Al and its alloys involving both classical hexavalent chromium-based solutions and the most recent ones involving transitional metals and/or rare earth compounds, as environmentally friendly alternatives. The main characteristics of the formed thin films, including appearance, composition, morphology, corrosion resistance, and performance, are also presented.

Cerium Chemical Conversion Coating for Aluminum Alloy 2024-T3 and Its Corrosion Resistance

CORROSION ◽  
2004 ◽  
Vol 60 (3) ◽  
pp. 237-243 ◽  
Author(s):  
C. Wang ◽  
F. Jiang ◽  
F. Wang
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Photoelectron Spectroscopy ◽  
Chemical Conversion ◽  
Spherical Particles ◽  
Conversion Coatings ◽  
Nacl Solution ◽  
X Ray ◽  
Golden Yellow ◽  
Aluminum Alloy 2024

Abstract New golden, yellow-colored cerium chemical conversion coatings on aluminum alloy 2024-T3 (AA2024-T3 [UNS A92024]) surface at room temperature were obtained by immersing the alloy into a cerium solution containing zinc chloride (ZnCl2) and hydrogen peroxide (H2O2). Electrochemical methods and immersion tests were used to study the dynamics of the coatings formation and their corrosion resistance in 3.5% sodium chloride (NaCl) solution. The morphologies of the coatings were recorded by scanning electronic microscopy (SEM). Energy-dispersive x-ray (EDX) analysis and x-ray photoelectron spectroscopy (XPS) were used to analyze the chemical composition and the oxidation state of the elements in the coatings. Polarization experiments and immersion tests in 3.5% NaCl solution showed that the sensitivity to pitting corrosion for the conversion-coated AA2024-T3 was greatly lower than that of the untreated specimens, and the corrosion resistance improved markedly. SEM photographs showed that the coatings consisted of a lot of spherical particles. EDX and XPS experimental results showed that the coatings were made up of oxygen, cerium, and aluminum, and the spherical particles contained higher contents of cerium and oxygen than the other sites. Cerium was mainly in the form of Ce4+. The mechanisms of conversion coatings formation and improvement on corrosion resistance also are discussed.

Preparation and corrosion resistance of titanium-zirconium/nickel-coated carbon nanotubes chemical nano-composite conversion coatings

2019 ◽  
Vol 66 (3) ◽  
pp. 343-351 ◽  
Author(s):  
Xiaobo Wang ◽  
Zhipeng Li ◽  
Wen Zhan ◽  
Jesong Tu ◽  
Xiaohua Zuo ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Special Functions ◽  
Chemical Conversion ◽  
Conversion Coatings ◽  
Nano Composite ◽  
Content Type ◽  
Titanium Zirconium ◽  
Coated Carbon

Purpose This study aims to expand the reliability and special functions of lightweight materials for high-end equipment and green manufacturing, so that it is the first such research to carry out nano-composite technology of nickel-coated carbon nanotubes (Ni-CNTs)-based titanium-zirconium chemical conversion on aluminum alloy substrate. Design/methodology/approach Corrosion behavior of various coatings was investigated using dropping corrosion test, linear polarization and electrochemical impedance spectroscopy. The results showed that the corrosion resistance of the nano-composite conversion coatings was significantly improved to compare with the conventional titanium-zirconium conversion coating. The morphology and microdomain characteristics of the nano-composite conversion coatings were characterized by SEM/eds/EPMA, which indicated that the CNT or Ni-CNTs addition promoting the integrity coverage of coatings in a short time. Findings Surface morphology of titanium-zirconium (Ti-Zr)/Ni-CNT specimens exhibited smooth, compact and little pores. The nano-composite conversion coatings are mainly composed of Al, O, C and Ti elements and contain a small amount of F and Zr elements, which illuminated that CNT or Ni-CNT addition could co-deposit with aluminum and titanium metal oxides. Originality/value The study of corrosion resistance of nano-composite conversion coatings and the micro-zone film-formation characteristics would be provided theoretical support for the development of basic research on surface treatment of aluminum alloys.

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