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.

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.

Wettability in pressure infiltration of SiC and oxidized SiC particle compacts by molten Al and Al-12wt%Si alloy

2007 ◽  
Vol 22 (8) ◽  
pp. 2273-2278 ◽  
Author(s):  
J.M. Molina ◽  
J. Tian ◽  
C. Garcia-Cordovilla ◽  
E. Louis ◽  
J. Narciso
Keyword(s):  
Contact Angle ◽  
Oxide Layer ◽  
Low Temperatures ◽  
Native Oxide ◽  
Native Oxide Layer ◽  
Threshold Pressure ◽  
Pressure Infiltration ◽  
Surface Conditions ◽  
Infiltration Behavior ◽  
Sic Particle

The infiltration behavior of compacts of SiC particles in two surface conditions, as-received and thermally oxidized, was investigated by using pure Al and Al-12wt%Si as infiltrating metals. Analysis of the threshold pressure for infiltration revealed that the process is governed by the same contact angle for all different systems, no matter the metal or particle condition. This leads to the conclusion that oxidation does not modify the wetting characteristics of the particles, most probably because they are already covered by a thin native oxide layer that remains unaltered in processing routes involving short contact times and low temperatures, such as actual conditions of pressure infiltration at 700 °C.

The Effect of Surface States on Secondary Electron (SE) Dopant Contrast from Silicon p-n Junctions

2007 ◽  
Vol 1026 ◽  
Author(s):  
Augustus K. W. Chee ◽  
Conny Rodenburg ◽  
Colin John Humphreys
Keyword(s):  
Oxide Layer ◽  
Computer Modelling ◽  
Surface States ◽  
Native Oxide ◽  
Native Oxide Layer ◽  
Element Analysis ◽  
Surface Band ◽  
Band Bending ◽  
Wide Range ◽  
Se Doping

AbstractDetailed computer modelling using finite-element analysis was performed for Si p-n junctions to investigate the effects of surface states and doping concentrations on surface band-bending, surface junction potentials and external patch fields. The density of surface states was determined for our Si specimens with a native oxide layer. Our calculations show that for a typical density of surface states for a Si specimen with a native oxide layer, the effects of external patch fields are negligible and the SE doping contrast is due to the built-in voltage across the p-n junction modified by surface band-bending. There is a good agreement between the experimental doping contrast and the calculated junction potential just below the surface, taking into account surface states, for a wide range of doping concentrations.

Nano-Thick Amorphous Oxide Layer Produced by Plasma on Type 316L Stainless Steel for Improved Corrosion Resistance Under Plastic Deformation

CORROSION ◽  
10.5006/2674 ◽  
2018 ◽  
Vol 74 (9) ◽  
pp. 1011-1022 ◽  
Author(s):  
Megan Mahrokh Dorri ◽  
Stéphane Turgeon ◽  
Maxime Cloutier ◽  
Pascale Chevallier ◽  
Diego Mantovani
Keyword(s):  
Plastic Deformation ◽  
Stainless Steel ◽  
Oxide Layer ◽  
Electrochemical Impedance ◽  
Open Circuit ◽  
Localized Corrosion ◽  
Native Oxide ◽  
Native Oxide Layer ◽  
Amorphous Oxide ◽  
Amorphous Oxide Layer

Localized corrosion constitutes a major concern in medical devices made of stainless steel. The conventional approach to circumvent such a problem is to convert the surface polycrystalline microstructure of the native oxide layer to an amorphous oxide layer, a few micrometers thick. This process cannot, however, be used for devices such as stents that undergo plastic deformation during their implantation, especially those used in vascular surgery for the treatment of cardiac, neurological, and peripheral vessels. This work explores the feasibility of producing a nano-thick plastic-deformation resistant amorphous oxide layer by plasma-based surface modifications. By varying the plasma process parameters, oxide layers with different features were produced and their properties were investigated before and after clinically-relevant plastic deformation. These properties and the related corrosion mechanisms were mainly evaluated using the electrochemical methods of open-circuit potential, cyclic potentiodynamic polarization, and electrochemical impedance spectroscopy. Results showed that, under optimal conditions, the resistance to corrosion and to the permeation of ions in a phosphate buffered saline, even after deformation, was significantly enhanced.

scholarly journals Эволюция физико-химических свойств поверхности GaSb(100) в растворах сульфида аммония

2019 ◽  
Vol 53 (7) ◽  
pp. 908
Author(s):  
М.В. Лебедев ◽  
Т.В. Львова ◽  
А.Л. Шахмин ◽  
О.В. Рахимова ◽  
П.А. Дементьев ◽  
...  
Keyword(s):  
Oxide Layer ◽  
Photoelectron Spectroscopy ◽  
Treatment Time ◽  
Solution Concentration ◽  
Native Oxide ◽  
Semiconductor Surface ◽  
Native Oxide Layer ◽  
Force Microscopy ◽  
Fermi Level Pinning ◽  
Ammonium Sulfide

AbstractVarious conditions of passivation of the GaSb(100) surface by ammonium sulfide ((NH_4)_2S) solutions depending on the solution concentration, solvent, and treatment time are investigated by X-ray photoelectron spectroscopy and atomic-force microscopy. It is shown that treatment of the GaSb(100) surface by any (NH_4)_2S solution leads to removal of the native oxide layer from the semiconductor surface and the formation of a passivating layer consisting of various gallium and antimony sulfides and oxides. The surface with the lowest roughness (RMS = 0.85 nm) is formed after semiconductor treatment with 4% aqueous ammonium sulfide solution for 30 min. Herewith, the atomic concentration ratio Ga/Sb at the surface is ~2. It is also found that aqueous ammonium sulfide solutions do not react with elemental antimony incorporated into the native-oxide layer. The latter causes a leakage current and Fermi-level pinning at the GaSb(100) surface. However, a 4% (NH_4)_2S solution in isopropanol removes elemental antimony almost completely; herewith, the semiconductor surface remains stoichiometric if a treatment duration is up to 13 min.

scholarly journals Photoluminescence properties of cuprous phosphide prepared through phosphating copper with a native oxide layer

RSC Advances ◽  
2021 ◽  
Vol 11 (54) ◽  
pp. 34095-34100
Author(s):  
Xue Peng ◽  
Yanfei Lv ◽  
Li Fu ◽  
Fei Chen ◽  
Weitao Su ◽  
...  
Keyword(s):  
Oxide Layer ◽  
Cuprous Oxide ◽  
Fluorescence Properties ◽  
Native Oxide ◽  
Native Oxide Layer ◽  
Photoluminescence Properties ◽  
Band Bending ◽  
Carrier Traps

The presence of cuprous oxide results in band bending at the interface between cuprous phosphide and cuprous oxide, forming carrier traps, which improves the fluorescence properties of cuprous phosphide.

Influence of Formative Native Oxide Layer on Mechanical Polished Cu Surface on Fluorescence Spectrum

2012 ◽  
Vol 41 (7) ◽  
pp. 874-877
Author(s):  
董军 DONG Jun ◽  
赵久强 ZHAO Jiuqiang ◽  
李绪强 LI Xuqiang ◽  
陈佳 Chen Jia ◽  
郑海荣 ZHENG Hairong
Keyword(s):  
Oxide Layer ◽  
Fluorescence Spectrum ◽  
Native Oxide ◽  
Native Oxide Layer
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