The Effect of Surface Treatment on the Performance of a Zirconium-Based Conversion Coating on AA7075 Automotive Alloys for Protection Against Filiform Corrosion

2020 ◽  
pp. 937-946 ◽  
Author(s):  
C. F. Glover ◽  
M. L. C. Lim ◽  
J. R. Scully
Keyword(s):  
Surface Treatment ◽  
Conversion Coating ◽  
Filiform Corrosion ◽  
Effect Of Surface

Increased Filiform Corrosion Resistance Utilizing a Zirconium-Based Conversion Coating on an Al-Zn-Mg-Cu (AA7075-T6) Alloy as well as Selected Surface Treatments

CORROSION ◽  
10.5006/3510 ◽  
2020 ◽  
Author(s):  
Carol Glover ◽  
Mary Lyn Lim ◽  
John Scully
Keyword(s):  
Surface Treatment ◽  
Photoelectron Spectroscopy ◽  
Conversion Coating ◽  
Surface Treatments ◽  
Treatment Processes ◽  
Filiform Corrosion ◽  
Alkaline Cleaning ◽  
Vinyl Butyral ◽  
Subsequent Acid ◽  
Effect Of Surface

This study investigates the effect of surface treatment on the formation of Zr-based conversion coatings on AA7075-T6 automotive aluminum alloys and their resistance to filiform corrosion (FFC). Two different surface treatments were studied (A) alkaline-cleaning and (B) alkaline-cleaning with a subsequent acid deoxidation step. A model poly-vinyl butyral (PVB) primer coating was used as the topcoat and specimens were studied with and without the application of a Zr-based conversion coating. Comparisons were made against a control that had no surface treatment. The FFC filament initiation time and propagation kinetics were of particular interest. Scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) were used to examine the conversion coating thickness and composition. A bi-layer conversion coating structure is demonstrated and both surface treatments are shown to produce copper enrichment that promotes the formation of the Zr-rich coating. Specimens prepared by alkaline cleaning-only resulted in a substantially thicker oxide layer of which 97% was ZrO2. These specimens provide superior resistance to FFC where the thick Zr-rich oxide is thought to provide a dense blocking layer that prevents electron transfer at the interface. In contrast, the control specimen, exposed only to the copper additions present in the conversion bath is shown to produce an Al oxide-rich layer with only a 33% ZrO2 contribution in the outer layer. The findings demonstrate that the redistribution of functional copper species, that is shown to occur during surface treatment processes, is crucial for the formation of a robust Zr film.

The Effect of Surface Treatment on the Performance of a Trivalent Chromium Process (TCP) Pretreatment on AA7075 Aerospace Alloys for the Protection Against Filiform Corrosion

CORROSION ◽  
10.5006/3380 ◽  
2019 ◽  
Vol 75 (12) ◽  
pp. 1513-1526 ◽  
Author(s):  
C.F. Glover ◽  
M.L.C. Lim ◽  
G. Post ◽  
M. Mayo ◽  
J.R. Scully
Keyword(s):  
Surface Treatment ◽  
Oxide Layer ◽  
Surface Characterization ◽  
Polyvinyl Butyral ◽  
Trivalent Chromium ◽  
Conversion Coating ◽  
Surface Treatments ◽  
Native Oxide ◽  
Native Oxide Layer ◽  
Filiform Corrosion

The performance of a trivalent chromium process (TCP) pretreatment conversion coating, applied to AA7075 aerospace aluminum alloys, for its ability to improve the filiform corrosion (FFC) of a polyvinyl-butyral coating, was studied as a function of surface treatment. Data from atmospheric FFC and full-immersion corrosion experiments are compared with surface characterization data to gain an understanding of the FFC kinetics on this alloy and mechanism by which the TCP coating provides inhibition. Specimens were prepared with three different surface treatments and studied with and without a TCP pretreatment conversion coating. A biphasic layer incorporating a zirconium-chromium mixed oxide outer layer and a fluoroaluminate interfacial layer was observed on all pretreated specimens. Enhanced corrosion protection by the TCP coating was observed when an acid pickle surface treatment was applied and the FFC filament propagation was stifled with an efficiency of 86%. A zirconium-rich outer oxide layer of approximately 22 nm, more than double the thickness of that measured for the other surface-treatments, is reported. Such layers are reported to be sufficiently dense so as to block ion transport from solution to the alloy surface. This acid pickle surface treatment is shown to effectively reduce the thickness of the native oxide layer and remove intermetallic particles from the surface enabling the formation of a more homogeneous TCP layer. Furthermore, Cu replating resulting from an acidic deoxidation step is shown to have no discernable effect on FFC.

scholarly journals Effect of surface treatments on push-out bond strength of calcium silicate-based cements to fiber posts

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Amr M. Elnaghy ◽  
Ayman Mandorah ◽  
Ali H. Hassan ◽  
Alaa Elshazli ◽  
Shaymaa Elsaka
Keyword(s):  
Bond Strength ◽  
Surface Treatment ◽  
Glass Fiber ◽  
Calcium Silicate ◽  
Surface Treatments ◽  
The Other ◽  
Fiber Posts ◽  
Glass Fiber Posts ◽  
Push Out ◽  
Effect Of Surface

Abstract Background To evaluate the effect of surface treatments on the push-out bond strength of Biodentine (BD) and white mineral trioxide aggregate (WMTA) to fiber posts. Methods Two brands of fiber posts were used: Reblida post; RP and RelyX post; RX. Each type of post (n = 80/group) was divided into four groups (n = 20/group) and exposed to surface treatment as follows: Control (no treatment), sandblasting (SB), hydrofluoric acid (HF), and TiF4 4 wt/v%. Each group was further subdivided into two subgroups (n = 10/subgroup) based on the type of CSCs used as follows: Subgroup A: BD and Subgroup B: WMTA. Push-out bond strength of BD and WMTA to glass fiber posts was assessed. Data were statistically analyzed using three-way ANOVA and Tukey’s test. A Weibull analysis was performed on the push-out bond strength data. Results BD showed higher bond strength than WMTA (P < 0.001). The push-out bond strength for posts treated with TiF4 4 wt/v% showed greater bond strength than the other surface treatments (P < 0.05). The BD/RP-TiF4 4 wt/v% showed the greater characteristic bond strength (σ0) (15.93) compared with the other groups. Surface treatments modified the surface topography of glass fiber posts. Conclusions The BD/RP-TiF4 4 wt/v% showed greater bond strength compared with the other groups. The TiF4 4 wt/v% surface treatment enhanced the bond strength of BD and WMTA to glass fiber posts than the other treatments. Surface treatment of fiber post with TiF4 4 wt/v% could be used to improve the bond strength with calcium silicate-based cements.

scholarly journals Repair bond strength of composite: Effect of surface treatment and type of composite

2018 ◽  
pp. 0-0
Author(s):  
M Ghavam ◽  
M Naeemi ◽  
SS Hashemikamangar ◽  
H Ebrahimi ◽  
MJ Kharazifard
Keyword(s):  
Bond Strength ◽  
Surface Treatment ◽  
Composite Effect ◽  
Effect Of Surface
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