An Optimized Trivalent Chromium Conversion Coating Process for AA2024-T351 Alloy

Jiantao Qi; Lei Gao; Y. Li; Zhengjian Wang; George Thompson; Peter Skeldon

doi:10.1149/2.1371707jes

An Optimized Trivalent Chromium Conversion Coating Process for AA2024-T351 Alloy

Jiantao Qi, Lei Gao, Y. Li, Zhengjian Wang, George Thompson, Peter Skeldon

Research output: Contribution to journal › Article › peer-review

Abstract

In this work, a trivalent chromium conversion coating applied on AA2024-T351 alloy has been optimized for corrosion protection in sodium chloride solutions. Scanning electron microscopy, energy dispersive X-ray spectroscopy and electrochemical measurements were employed to characterize the coating. An immersion post-treatment of the coated alloy in 40 ºC deionized water for 120 s considerably enhanced the corrosion protection properties, compared with a post treatment at 20 °C, or the absence of a post-treatment. Electrochemical noise measurements, combined with real time imaging, and potentiodynamic polarization experiments indicated a conversion treatment for 300 or 600 s provides optimal corrosion protection. Relatively long conversion treatments decreased the corrosion protection due to an increase in coating defects and cracks, especially around the second-phase particles.

Original language	English
Journal	Journal of the Electrochemical Society
DOIs	https://doi.org/10.1149/2.1371707jes
Publication status	Published - 1 Jun 2017

Keywords

Coating process
AA2024 alloy
Corrosion protection
Electrochemical Impedance
Electrochemical noise

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10.1149/2.1371707jesLicence: CC BY

Light Alloys towards environmentally sustainable transport: 2nd generation solutions for Advanced Metallic Systems ( LATEST 2 )
Thompson, G. (PI), Bate, P. (CoI), Prangnell, P. (CoI), Preuss, M. (CoI), Quinta Da Fonseca, J. (CoI), Robson, J. (CoI), Skeldon, P. (CoI) & Zhou, X. (CoI)
1/02/10 → 31/07/15
Project: Research

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title = "An Optimized Trivalent Chromium Conversion Coating Process for AA2024-T351 Alloy",

abstract = "In this work, a trivalent chromium conversion coating applied on AA2024-T351 alloy has been optimized for corrosion protection in sodium chloride solutions. Scanning electron microscopy, energy dispersive X-ray spectroscopy and electrochemical measurements were employed to characterize the coating. An immersion post-treatment of the coated alloy in 40 ºC deionized water for 120 s considerably enhanced the corrosion protection properties, compared with a post treatment at 20 °C, or the absence of a post-treatment. Electrochemical noise measurements, combined with real time imaging, and potentiodynamic polarization experiments indicated a conversion treatment for 300 or 600 s provides optimal corrosion protection. Relatively long conversion treatments decreased the corrosion protection due to an increase in coating defects and cracks, especially around the second-phase particles.",

keywords = "Coating process, AA2024 alloy, Corrosion protection, Electrochemical Impedance, Electrochemical noise",

author = "Jiantao Qi and Lei Gao and Y. Li and Zhengjian Wang and George Thompson and Peter Skeldon",

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AU - Qi, Jiantao

AU - Gao, Lei

AU - Li, Y.

AU - Wang, Zhengjian

AU - Thompson, George

AU - Skeldon, Peter

PY - 2017/6/1

Y1 - 2017/6/1

N2 - In this work, a trivalent chromium conversion coating applied on AA2024-T351 alloy has been optimized for corrosion protection in sodium chloride solutions. Scanning electron microscopy, energy dispersive X-ray spectroscopy and electrochemical measurements were employed to characterize the coating. An immersion post-treatment of the coated alloy in 40 ºC deionized water for 120 s considerably enhanced the corrosion protection properties, compared with a post treatment at 20 °C, or the absence of a post-treatment. Electrochemical noise measurements, combined with real time imaging, and potentiodynamic polarization experiments indicated a conversion treatment for 300 or 600 s provides optimal corrosion protection. Relatively long conversion treatments decreased the corrosion protection due to an increase in coating defects and cracks, especially around the second-phase particles.

AB - In this work, a trivalent chromium conversion coating applied on AA2024-T351 alloy has been optimized for corrosion protection in sodium chloride solutions. Scanning electron microscopy, energy dispersive X-ray spectroscopy and electrochemical measurements were employed to characterize the coating. An immersion post-treatment of the coated alloy in 40 ºC deionized water for 120 s considerably enhanced the corrosion protection properties, compared with a post treatment at 20 °C, or the absence of a post-treatment. Electrochemical noise measurements, combined with real time imaging, and potentiodynamic polarization experiments indicated a conversion treatment for 300 or 600 s provides optimal corrosion protection. Relatively long conversion treatments decreased the corrosion protection due to an increase in coating defects and cracks, especially around the second-phase particles.

KW - Coating process

KW - AA2024 alloy

KW - Corrosion protection

KW - Electrochemical Impedance

KW - Electrochemical noise

U2 - 10.1149/2.1371707jes

DO - 10.1149/2.1371707jes

M3 - Article

SN - 0013-4651

JO - Journal of the Electrochemical Society

JF - Journal of the Electrochemical Society

ER -

An Optimized Trivalent Chromium Conversion Coating Process for AA2024-T351 Alloy

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Light Alloys towards environmentally sustainable transport: 2nd generation solutions for Advanced Metallic Systems ( LATEST 2 )

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