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Role of Hydrogen in Intergranular Corrosion of AA2024 Aluminium Alloy: An AFM-KFM Study

A powerful way to study hydrogen embrittlement at a local scale is by Scanning Kelvin Probe Force Microscopy (SKPFM). This technique by measuring the surface potential at the nanometer scale allows the detection and localization of hydrogen in the alloy.

Product Number: 51317--9464-SG
ISBN: 9464 2017 CP
Author: Christine BLANC
Publication Date: 2017
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$20.00
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Hydrogen embrittlement is suspected to play a major role in the corrosion of aluminium alloys. This work aims at determining the influence of hydrogen on the corrosion damage of AA2024 aluminium alloy a commonly used alloy in aeronautics. A powerful way to study hydrogen embrittlement at a local scale is by combining atomic force microscope and Kelvin probe force microscope (AFM-KFM). This technique by measuring the surface potential at the nanometer scale allows the detection and localization of hydrogen in the alloy. Firstly AFM-KFM measurements were taken on model materials containing a controlled quantity of hydrogen. Hydrogen was inserted into AA2024 alloy via cathodic charging in H2SO4 through one of the short transverse (ST)/ long transverse (LT) sides. AFM-KFM images taken on the side perpendicular (ST/rolling direction (RD)) revealed a surface potential gradient over a few hundreds of microns due to a hydrogen gradient in the material. Results showing the evolution of the gradient as a function of the charging duration will be presented. The desorption kinetics of hydrogen once inserted followed via the evolution of the surface potential gradient as a function of temperature will also be shown. These AFM-KFM measurements coupled with the hydrogen dosing by fusion method in order to get the exact hydrogen content give fundamental information about the diffusion and trapping of atomic hydrogen in the alloy. The AFM-KFM technique was then used to detect hydrogen in the corrosion defect of alloys exposed to an aggressive environment. These measurements allow to determine the influence of the hydrogen on the propagation kinetics of intergranular corrosion defects in a 2024-T351 aluminium alloy exposed to conditions similar to an aircraft in-service ones.This work is supported by ANR-14-CE07-0027-01 – M-SCOT: Multi Scale COrrosion Testing.

Key words: Aluminum alloys, Hydrogen desorption, Scanning Kelvin Probe Force Microscopy (SKPFM), Intergranular corrosion, Hydrogen embrittlement

Hydrogen embrittlement is suspected to play a major role in the corrosion of aluminium alloys. This work aims at determining the influence of hydrogen on the corrosion damage of AA2024 aluminium alloy a commonly used alloy in aeronautics. A powerful way to study hydrogen embrittlement at a local scale is by combining atomic force microscope and Kelvin probe force microscope (AFM-KFM). This technique by measuring the surface potential at the nanometer scale allows the detection and localization of hydrogen in the alloy. Firstly AFM-KFM measurements were taken on model materials containing a controlled quantity of hydrogen. Hydrogen was inserted into AA2024 alloy via cathodic charging in H2SO4 through one of the short transverse (ST)/ long transverse (LT) sides. AFM-KFM images taken on the side perpendicular (ST/rolling direction (RD)) revealed a surface potential gradient over a few hundreds of microns due to a hydrogen gradient in the material. Results showing the evolution of the gradient as a function of the charging duration will be presented. The desorption kinetics of hydrogen once inserted followed via the evolution of the surface potential gradient as a function of temperature will also be shown. These AFM-KFM measurements coupled with the hydrogen dosing by fusion method in order to get the exact hydrogen content give fundamental information about the diffusion and trapping of atomic hydrogen in the alloy. The AFM-KFM technique was then used to detect hydrogen in the corrosion defect of alloys exposed to an aggressive environment. These measurements allow to determine the influence of the hydrogen on the propagation kinetics of intergranular corrosion defects in a 2024-T351 aluminium alloy exposed to conditions similar to an aircraft in-service ones.This work is supported by ANR-14-CE07-0027-01 – M-SCOT: Multi Scale COrrosion Testing.

Key words: Aluminum alloys, Hydrogen desorption, Scanning Kelvin Probe Force Microscopy (SKPFM), Intergranular corrosion, Hydrogen embrittlement

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