TY - JOUR
T1 - Multistep anodization of 7075 – T6 aluminum alloy
AU - Totaro, Peter
AU - Khusid, Boris
N1 - Funding Information:
The authors are thankful to Dr. Mirko Schoenitz (New Jersey Institute of Technology, New Jersey) for providing data on the instrumental peak broadening in XRD measurements and Qian Lei (New Jersey Institute of Technology, New Jersey) for providing guidelines on image processing and analysis with ImageJ. This research did not receive any specific grant from funding agencies in the public, commercial, or not- for-profit sectors.
Publisher Copyright:
© 2021 The Author(s)
PY - 2021/9/15
Y1 - 2021/9/15
N2 - This study successfully demonstrated the overall advantages of multistep anodization of heat-treated wrought aluminum alloy AA7075-T6 that is a widely used in aerospace, automotive and fracture-critical applications. The coating properties and morphology are studied in detail for four anodization regimes: a conventional R1 with a constant electric current and R2, R3, R4 with raising the current in two, four and eight steps, respectively. Whereas processes R1 and R2 form coatings with the atomic Al/O ratio of 0.53 that is smaller than 0.67 for oxide Al2O3, R3 and R4 create coatings with the Al/O ratio of 0.83. Due to a higher level of infused oxygen, coatings built in R1 and R2 have burns and powdery appearance, while coatings formed in processes R3 and R4 form exhibit smooth solid-like surfaces. Compared to R1 and R2, R3 and R4 increase the overall growth rate of oxides by 23.4% and 25.6%, respectively, reduce the pore size by 94% and 45% respectively and decrease by 8.4% the amount of a transferred electric charge per one micrometer of the layer thickness. Process R4 creates coatings that are 74.0% more resistant to abrasion, 14.6% harder and 25.4% thicker than coatings formed in R1. As no specialized equipment is required, presented regimes of multistep anodization are well suited for large-scale manufacturing.
AB - This study successfully demonstrated the overall advantages of multistep anodization of heat-treated wrought aluminum alloy AA7075-T6 that is a widely used in aerospace, automotive and fracture-critical applications. The coating properties and morphology are studied in detail for four anodization regimes: a conventional R1 with a constant electric current and R2, R3, R4 with raising the current in two, four and eight steps, respectively. Whereas processes R1 and R2 form coatings with the atomic Al/O ratio of 0.53 that is smaller than 0.67 for oxide Al2O3, R3 and R4 create coatings with the Al/O ratio of 0.83. Due to a higher level of infused oxygen, coatings built in R1 and R2 have burns and powdery appearance, while coatings formed in processes R3 and R4 form exhibit smooth solid-like surfaces. Compared to R1 and R2, R3 and R4 increase the overall growth rate of oxides by 23.4% and 25.6%, respectively, reduce the pore size by 94% and 45% respectively and decrease by 8.4% the amount of a transferred electric charge per one micrometer of the layer thickness. Process R4 creates coatings that are 74.0% more resistant to abrasion, 14.6% harder and 25.4% thicker than coatings formed in R1. As no specialized equipment is required, presented regimes of multistep anodization are well suited for large-scale manufacturing.
KW - Aerospace aluminum alloys
KW - Anodizing
KW - Current density
KW - Intermetallics
KW - Ramping
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U2 - 10.1016/j.surfcoat.2021.127407
DO - 10.1016/j.surfcoat.2021.127407
M3 - Article
AN - SCOPUS:85107929360
SN - 0257-8972
VL - 421
JO - Surface and Coatings Technology
JF - Surface and Coatings Technology
M1 - 127407
ER -