Alumina Sol-Gel Films and Alodine Films on Al 2024 Alloy

2011 ◽  
Vol 356-360 ◽  
pp. 364-367
Author(s):  
Qi Zhou ◽  
Xuan Xiao ◽  
Da Li Zhao ◽  
En Jun Song
Keyword(s):  
Corrosion Resistance ◽  
Aluminium Alloy ◽  
Electrochemical Impedance ◽  
Sol Gel ◽  
Film Surface ◽  
Corrosion Current ◽  
Promising Alternative ◽  
Gel Film ◽  
Alumina Sol ◽  
Sol Gel Films

Development of the sol-gel films for painting pretreatment of aluminium alloy is to replace bichromate conversion films such as Alodine. Corrosion resistance of Alodine film and sol-gel film were evaluated through potentiodynamic polarization curves, electrochemical impedance spectroscopy, salt spraying and acidic dropping solution. Sol-gel film is almost the same as Alodine film at the film surface density, salt spraying resistance and adhesion with painting coating. Changing color times of dropping solution on sol-gel film is shorter than Alodine film. But the corrosion current of sol-gel film is lower than Alodine and the impedance value is higher than Alodine in 35g/L NaCl solution. Mechanism of corrosion resistance of alumina sol-gel film is that the cathode reaction and anodic reactions are restrained by sol-gel film in the Cl- corrosive medium. The EIS of sol-gel film consisted of only a single capacitive arc with one time constant. Sol-gel coating can prevent or delay the corrosive solution from infiltrating the substrate for its better isolation function, thus protecting 2024 aluminium alloy from corrosion. Sol-gel films can improve corrosion resistance of aluminum alloy and have the same adhesion as Alodine film. It will be a promising alternative pretreatment for aluminum alloys prior to painting.

Effect of Nanoparticle Addition in Hybrid Sol-Gel Silane Coating on Corrosion Resistance of Low Carbon Steel

2013 ◽  
Vol 686 ◽  
pp. 244-249 ◽  
Author(s):  
Poovarasi Balan ◽  
Aaron Ng ◽  
Chee Beng Siang ◽  
R.K. Singh Raman ◽  
Eng Seng Chan
Keyword(s):  
Corrosion Resistance ◽  
Carbon Steel ◽  
Electrochemical Impedance ◽  
Sol Gel ◽  
Low Carbon Steel ◽  
Electrochemical Corrosion ◽  
Alumina Nanoparticles ◽  
Low Carbon ◽  
Silane Coating ◽  
Sol Gel Films

Chromium pre-treatments of metal have been replaced by silane pre-treatments as more environmental friendly option. Nanoparticles can be added in the silane sol-gel network have been reported to improve corrosion resistance. In this work, the electrochemical corrosion resistance of low carbon steel coated with hybrid organic-inorganic sol-gel film filled with nanoparticles was evaluated. The sol-gel films have been synthesized from 3-glycidoxy-propyl-trimethoxy-silane (3-GPTMS) and tetra-ethyl-ortho-silicate (TEOS) precursors. These films have been impregnated with 300 ppm of silica or alumina nanoparticles. The electrochemical behavior of the coated steel was evaluated by means of electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Equivalent circuit modeling, used for quantifying the EIS measurements showed that sol-gel films containing silica nanoparticles improved the barrier properties of the silane coating. The silica nanoparticle-containing films showed highest initial pore resistance over the five days of immersion in 0.05M NaCl.

Effect of Sol-Gel Film on the Corrosion Resistance of Low Carbon Steel Plate

2020 ◽  
Vol 984 ◽  
pp. 43-50
Author(s):  
Hua Yuan Zhang ◽  
Can Wang ◽  
Bing Xue ◽  
Jing Luo
Keyword(s):  
Corrosion Resistance ◽  
Carbon Steel ◽  
Steel Plate ◽  
Salt Spray ◽  
Sol Gel ◽  
Low Carbon Steel ◽  
Corrosion Current ◽  
Neutral Salt ◽  
Low Carbon ◽  
Gel Film

To improve the corrosion resistance on Q235 low carbon steel, in this paper, tetraethyl orthosilicate (TEOS), N-dodecyl trimethoxysilane and γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH560) were used to make organic-inorganic hybrid sol-gel film. Cross cut test adhesion method, neutral salt spray test, electrochemical test and film protective efficiency were taken to value the corrosion resistance property. The corrosion topography was studied by optical microscope. In addition, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) curves and equivalent electric circuit fitting were used to analyze the corrosion mechanism. The cross cut adhesion of sol-gel film can reach 1 class and the protection class can attain 5 class after 72 hours neutral salt spray test. According to the potentiodynamic polarization curve analysis, the corrosion potential of sol-gel film coating sample after 0.5 hours immersion was -0.46 V (vs. SCE) on the 0.1 Hz, and its corrosion current density was 4.74×10-7 A·cm-2. The corrosion potential of bare Q235 low carbon steel plate after 0.5 hours immersion was -0.78 V (vs. SCE) on the 0.1 Hz, and its corrosion current density was 4.75×10-6 A·cm-2. The impedance value on 0.1 Hz (|Z|0.1Hz) (1.27×106 Ω·cm2) of sol-gel film coating sample was more than three orders of magnitude higher than the value of the low carbon steel plate. Even dipping in 3.5 wt. % NaCl for 72 hours, the |Z|0.1Hz value of sol-gel coating sample was still one order of magnitude higher than the low carbon steel plate with 0.5 hours immersion. Sol-gel film with excellent adhesion can significantly improve the corrosion resistance of low carbon steel plate. Sol-gel film can increase the protection efficiency of low carbon steel plate by 90%.

Sol-Gel Films Prepared with Pure Alumina Sol by Re-Dissolution on Aluminum Alloy

2011 ◽  
Vol 382 ◽  
pp. 332-335
Author(s):  
Qi Zhou ◽  
Hong Liang Zhao ◽  
En Jun Song ◽  
Xiu Lian Chen
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Hexavalent Chromium ◽  
Paint Film ◽  
Sol Gel ◽  
Aluminum Nitrate ◽  
Dry Adhesion ◽  
Film Adhesion ◽  
Gel Film ◽  
Alumina Sol

The development of non-hexavalent chromium conversion coating on aluminum alloy is imminent, hexavalent chromium Cr6+ compounds have serious threat to the environment. The appearances, viscosity, particle size of aluminum nitrate sol prepared by re-dissolving were tested by orthogonal experiment. The results show that a better condition for preparing sol by re-dissolving the aluminum nitrate sol is: [Al3+] of 0.3mol/L, sol at 55~85°C or 0.6mol/L, at 55°C. The pH value ranges 7~9 before re-dissolving. The salt spraying resistance for the sol-gel film prepared by sol of which viscosity ranges 4.8 ~ 6 mPa/s is better than five grade. The dry adhesion for paint film is qualified when viscosity ≤ 5.6 mPa/s and the average size of particles <920 nm for sol. In terms of sol appearance, dry adhesion and salt spray properties of the sol-gel film made by blue and white or gray sol are good. [Al3+] concentration and sol temperature for preparing sol-gel film with better corrosion resistance are equally important, secondly is pH before re-dissolved. Dry adhesion between paint film and aluminum alloy is qualified when [Al3+] ranges 0.3 ~0.6mol/L. Corrosion resistance for alumina sol-gel film of [Al3+] concentration of 0.3 and 0.77mol/L is worse than that of 0.6mol/L. The times of spray coating has no influence on corrosion resistance, while the increased frequency of coating times, and film adhesion decrease. In short, if you want that painting film adhesion and corrosion resistance are both good, Al3+ concentration should be 0.6mol/L for pure aluminum sol. The preferable prepared conditions are that aging at 55 °C, pH of sol re-dissolved with nitric acid is 4 after adding ammonia until pH reaches 8, coated one times, two or more times, the adhesion of the coating will reduce.

Alumina Sol-Gel Film for Pretreatment to Paint on Aluminum Alloy

2011 ◽  
Vol 239-242 ◽  
pp. 1678-1681 ◽  
Author(s):  
Qi Zhou ◽  
Ping Zhao ◽  
Chun Lin He ◽  
Qing Kui Cai
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Paint Film ◽  
Sol Gel ◽  
Single Layer ◽  
Double Layers ◽  
Pure Alumina ◽  
Layer Composite ◽  
Gel Film ◽  
Alumina Sol

Aluminum alloy coatings for pretreatment are developed by sol-gel method. The adhesion between sol-gel film and the paint film was measured by scratching circles and corrosion resistance of sol-gel film was tested by salt spraying experiment. The adhesion between sol-gel film made by pure alumina sol and the paint film was so poor that it is unsuitable for ground coatings, but the composite sol which ultrafine Al2O3 powder was added to pure alumina sol can improve the adhesion and corrosion resistance. If the first layer film is made of pure alumina sol and the second layer is made of composite sol, the neutral salt spraying time of double layers film is longer than the single-layer composite sol-gel film. The adhesion for both double composite film and single-layer composite sol-gel film are first-grade. When solution of potessium dichromate is dropped on double combinatorial film for 100s, the solution will change in color. The gloss of paint film on double composite sol-gel film is 0.827, flexibility is 2×10mm and impact resistance is 1kg∙50cm. It is possible that composite sol-gel film or combinatorial sol-gel film replace dichromate salt conversion film on aluminum alloy using for painting pretreatment.

Effect of coating composition on the anticorrosion performance of a silane sol–gel layer on mild steel

RSC Advances ◽  
2015 ◽  
Vol 5 (129) ◽  
pp. 106485-106491 ◽  
Author(s):  
A. Foroozan E. ◽  
R. Naderi
Keyword(s):  
Mild Steel ◽  
Electrochemical Impedance ◽  
Steel Substrate ◽  
Sol Gel ◽  
Gel Layer ◽  
Gel Film ◽  
Coating Composition ◽  
Anticorrosion Performance ◽  
Protective Performance ◽  
Mild Steel Substrate

In this study, the effect of coating composition on the protective performance of an eco-friendly silane sol–gel film applied on a mild steel substrate was investigated using electrochemical impedance spectroscopy and surface analysis methods.

Effect of Shot Peening on Microstructure and Properties of 34CrMo4 Alloy

2018 ◽  
Vol 934 ◽  
pp. 105-110 ◽  
Author(s):  
Ke Jian Li ◽  
Qiang Zheng ◽  
Yue Lin Qin ◽  
Xiao Wei Liu
Keyword(s):  
Plastic Deformation ◽  
Corrosion Resistance ◽  
Shot Peening ◽  
Electrochemical Impedance ◽  
Corrosion Current ◽  
Optical Microscope ◽  
Microstructure And Properties ◽  
Before And After ◽  
Sever Plastic Deformation ◽  
Evolution Of Microstructure

Plastic deformation can induce surface modification, such as shot peening (SP) on workpiece surface is the hot issue of recent scientific research. SP is the efficient way to improve mechanical behavior of specimens by inducing sever plastic deformation on their surface. Nevertheless, this surface treatment induced complex microstructural evolutions such as grain refinement, will enhance the corrosion resistance of specimens. In this work, the microstructure and properties of 34CrMo4 alloy of before and after SP for 20 min have been investigated. The evolution of microstructure and properties were analyzed from the surface and cross-section. The microstructure morphology at the different depth was determined by optical microscope. The results show grain size is increasing with the depth, and the microhardness and compressive residual stress decrease gradually. In terms of corrosion resistance, the 50 μm depth specimen has the best property than other depth, which the potential and corrosion current density are-0.484 V and-5.72 Acm-2, respectively. The maximum polarization resistance is 2055 Ωcm2by capacitive arc radius of electrochemical impedance spectroscopy.

Effects of potassium silicate on corrosion behavior of dacromet coating

2019 ◽  
Vol 66 (6) ◽  
pp. 819-826
Author(s):  
Khashayar Tabi ◽  
Mansour Farzam ◽  
Davood Zaarei
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Behavior ◽  
Automobile Industry ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Corrosion Current ◽  
Potassium Silicate ◽  
Coated Steel ◽  
Content Type ◽  
New Information

Purpose Potassium silicate sealer was applied on solvent-cleaned, acid-pickled, dacromet-coated steel to improve its corrosion resistance. The purpose of this paper is to study the corrosion behavior of dacromet-coated steel. Design/methodology/approach Potassium silicate sealer was applied on solvent-cleaned, acid-pickled, dacromet-coated steel to improve its corrosion resistance. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and salt spray were carried out. SEM was used to study the morphological appearance of the surface. Findings The EIS behavior indicated that solvent-cleaned dacromet-coated steel sealed with potassium silicate showed that the corrosion current density was 2.664E − 5 A.cm2 which was reduced to 8.752E − 6 A.cm2 and the corrosion rate, which was 2.264E − 2 mm.year−1, was reduced to 7.438E − 3 mm.year−1 in NaCl 3.5 wt.per cent. EIS was used in NaCl 3.5 wt.%, and the Bode plot characteristics showed that the corrosion protection of solvent-cleaned, dacromet-coated steel was enhanced when sealed with potassium silicate. The EDS results of salt-sprayed, solvent-cleaned samples after 10 days indicated that the main corrosion products are composed of SiO2, ZnO and Al2O3. Research limitations/implications The detection of Li element in EDS was not possible because of the device limitation. Originality/value The current paper provides new information about the sealing properties of potassium silicate and its effects on the corrosion resistance of dacromet coating, which is widely used in many industries such as the automobile industry.

Preparation, characterization, and micropatterning of laser-dye-doped sol-gel films

2002 ◽  
Vol 17 (8) ◽  
pp. 2095-2098 ◽  
Author(s):  
A. Arena ◽  
S. Patanè ◽  
G. Saitta ◽  
G. Rizzo ◽  
S. Galvagno ◽  
...  
Keyword(s):  
Soft Lithography ◽  
Sol Gel ◽  
Film Surface ◽  
Optical Microscope ◽  
Infrared Range ◽  
Patterned Films ◽  
A Charge ◽  
Sol Gel Films ◽  
Sol Gel Synthesis ◽  
Micrometer Scale

Planar thin films of dye-doped silica were prepared by sol-gel synthesis. The optical properties of the films were characterized by transmittance measurements in the visible-infrared range and by photoluminescence. Micropatterns whose feature size was on the order of 2.4 μm, were imprinted on the film surface by a simple soft lithography approach. An optical microscope interfaced to a charge-coupled device camera was used to image the imprinted patterns and to analyze the patterned films photoluminescence. A sensitive spectral narrowing of the emission, which occurred only in micropatterned films, was attributed to the lateral confinement of the luminescence due to the micrometer-scale modulation of refractive index produced by the embossing procedure.

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