Characterization of a Chromium-Free Passivation Coating on Hot Dip Al-Zn Allay Coated Steel Sheets

2013 ◽  
Vol 634-638 ◽  
pp. 2931-2934
Author(s):  
Ping Yuan
Keyword(s):  
Salt Spray ◽  
Optical Emission ◽  
Acrylic Resin ◽  
Organic Coating ◽  
Neutral Salt ◽  
Coated Steel ◽  
Corrosion Performance ◽  
Steel Sheets ◽  
Coated Steel Sheet ◽  
Passivation Coating

The hot dip Al-Zn alloy coated steel sheet was passivated with chromium-free passivation solution which adopted the molybdate and acrylic resin as the main film-forming substances. The surface morphology and corrosion performance of the coating were studied experimentally by using glow discharge optical emission spectroscopy(GD-OES), scanning electron microscopy(SEM) and energy-dispersive X-ray spectroscopy(EDS), polarization curves and the neutral salt spray test. The GD-OES and SEM results show that the molybdate-containing thin organic coating is deposited on the substrate compactly and homogeneously without obvious tiny cracks. The test results of corrosion performance show that the corrosion potential and current density of the passive films decrease obviously in comparison with those of the substrate, and the corrosion resistance of the coating is comparable with that of the chromate passivation coating.

Corrosion Performance of Common Pressed Prepainted Steel Sheet

2012 ◽  
Vol 193-194 ◽  
pp. 458-461
Author(s):  
Hui Ping Bai ◽  
Zhong Hua Zheng ◽  
Yuan Qiang Tu ◽  
Jie Cai
Keyword(s):  
Electrochemical Impedance Spectroscopy ◽  
Steel Sheet ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Optical Emission ◽  
Trade Mark ◽  
Emission Spectrometry ◽  
Neutral Salt ◽  
Corrosion Performance ◽  
Steel Sheets

The corrosion behavior of common pressed prepainted steel sheets with trade mark TDC51D+Z was studied by neutral salt spray and electrochemical impedance spectroscopy (EIS). The effect of organic polymers on the corrosion performance of prepainted steel sheet was analyzed with glow discharge optical emission spectrometry (GDS). The results showed that the distributing depth of titanium pigment determined the corrosion performance of prepainted steel sheets with white finishing coat.

Influence of Zinc Content on Anti-Corrosion Performance of Zinc-Rich Coatings

2013 ◽  
Vol 423-426 ◽  
pp. 169-172
Author(s):  
Guo Xin Li ◽  
Bing Jie Li ◽  
Yi Liang Peng ◽  
Wei Tong Yue
Keyword(s):  
Electron Microscope ◽  
Steel Substrate ◽  
Salt Spray ◽  
Zinc Content ◽  
Acrylic Resin ◽  
Zinc Powder ◽  
Neutral Salt ◽  
Corrosion Performance ◽  
Amino Resin ◽  
Scanning Electron

The zinc-rich coating prevents steel from corrosion by sacrificing electrochemical cathode anode protection, but the zinc content is the most important parameter. In this paper, the zinc-rich coatings made with the amino resin, acrylic resin, complex solvents, auxiliary agents and high purity zinc powder. The coatings were applied onto steel substrate and then placed in neutral salt spray for 3000 h in order to study the anti-corrosion performance. The results showed that the anti-corrosion performance was promoted with the zinc content increasing. When the zinc content was higher than 86 wt. %, the anti-corrosion performance can be reached 3000 h. The anticorrosion mechanisms were studied by polarization curves and scanning electron microscope (SEM).

scholarly journals Aggressiveness of Different Ageing Conditions for Three Thick Marine Epoxy Systems

2021 ◽  
Vol 2 (4) ◽  
pp. 721-742
Author(s):  
Alexis Renaud ◽  
Victor Pommier ◽  
Jérémy Garnier ◽  
Simon Frappart ◽  
Laure Florimond ◽  
...  
Keyword(s):  
Salt Spray ◽  
Immersion Test ◽  
Organic Coating ◽  
Artificial Seawater ◽  
Galvanized Steel ◽  
Natural Seawater ◽  
Neutral Salt ◽  
Coating System ◽  
Coated Steel ◽  
Artificial Defect

Three different coated steel systems were aged in natural or artificial seawater, in neutral salt spray (NSS), and using alternate immersion tests in order to evaluate the aggressiveness of the different ageing conditions. Commercial epoxy coatings were applied onto steel (S355NL), hot-galvanized steel (HDG), and Zn-Al15 thermal spraying coated steel. The defect-free systems were immersed in artificial seawater at 35 °C for 1085 days and in natural seawater for 1200 days and were characterized by electrochemical impedance spectroscopy (EIS). Panels with artificial defects were immersed for 180 days in artificial seawater and, regarding adhesion, were evaluated according to ISO 16276-2. In parallel, the three coated systems were submitted to cyclic neutral salt spray (NSS) for 1440 h: defect-free panels were regularly evaluated by EIS, while the degree or corrosion was measured onto panels with artificial defect. After NSS, defect-free panels were immersed in artificial seawater at 35 °C for further EIS investigations. Finally, alternate immersion tests were performed for 860 days for the three defect-free coated systems and for 84 days for panels with a defect. The results showed that, for defect-free panels, immersions in natural or artificial seawater and NSS did not allowed us to distinguish the three different systems that show excellent anticorrosion properties. However, during the alternate immersion test, the organic coating system applied onto HDG presented blisters, showing a greater sensitivity to this test than the two other systems. For panels with a defect, NSS allowed to age the coatings more rapidly than monotone conditions, and the coating system applied onto steel presented the highest degree of corrosion. Meanwhile, the coating systems applied onto HDG and the thermal spray metallic coating showed similar behavior. During the alternate immersion test, the three coated systems with a defect showed clearly different behaviors, therefore it was possible to rank the three systems. Finally, it appeared that the alternate immersion test was the most aggressive condition. It was then proposed that a realistic thermal cycling and an artificial defect are needed when performing ageing tests of thick marine organic coating systems in order to properly rank/evaluate the different systems.

scholarly journals Application of Commercial Surface Pretreatments on the Formation of Cerium Conversion Coating (CeCC) over High-Strength Aluminum Alloys 2024-T3 and 7075-T6

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 930
Author(s):  
Juan Jesús Alba-Galvín ◽  
Leandro González-Rovira ◽  
Francisco Javier Botana ◽  
Maria Lekka ◽  
Francesco Andreatta ◽  
...  
Keyword(s):  
Electrochemical Impedance ◽  
Salt Spray ◽  
Aluminum Matrix ◽  
Optical Emission ◽  
High Strength ◽  
Chemical Conversion ◽  
Conversion Coating ◽  
Neutral Salt ◽  
Corrosion Properties ◽  
Surface Pretreatment

The selection of appropriate surface pretreatments is one of the pending issues for the industrial application of cerium-based chemical conversion coatings (CeCC) as an alternative for toxic chromate conversion coating (CrCC). A two-step surface pretreatment based on commercial products has been successfully used here to obtain CeCC on AA2024-T3 and AA7075-T6. Specimens processed for 1 to 15 min in solutions containing CeCl3 and H2O2 have been studied by scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDX), glow discharge optical emission spectroscopy (GDOES), potentiodynamic linear polarization (LP), electrochemical impedance spectroscopy (EIS), and neutral salt spray (NSS) tests. SEM-EDX showed that CeCC was firstly observed as deposits, followed by a general coverage of the surface with the formation of cracks where the coating was getting thicker. GDOES confirmed an increase of the CeCC thickness as the deposition proceed, the formation of CeCC over 7075 being faster than over 2024. There was a Ce-rich layer in both alloys and an aluminum oxide/hydroxide layer on 7075 between the upper Ce-rich layer and the aluminum matrix. According to LP and EIS, CeCC in all samples offered cathodic protection and comparable degradation in chloride-containing media. Finally, the NSS test corroborated the anti-corrosion properties of the CeCC obtained after the commercial pretreatments employed.

The corrosion protection of AA2024-T3 aluminium alloy by leaching of lithium-containing salts from organic coatings

2015 ◽  
Vol 180 ◽  
pp. 511-526 ◽  
Author(s):  
Peter Visser ◽  
Yanwen Liu ◽  
Xiaorong Zhou ◽  
Teruo Hashimoto ◽  
George E. Thompson ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Salt Spray ◽  
Protective Layer ◽  
Middle Layer ◽  
Organic Coating ◽  
Organic Coatings ◽  
Inhibition Mechanism ◽  
Dense Layer ◽  
Neutral Salt ◽  
Protective Layers

Lithium carbonate and lithium oxalate were incorporated as leachable corrosion inhibitors in model organic coatings for the protection of AA2024-T3. The coated samples were artificially damaged with a scribe. It was found that the lithium-salts are able to leach from the organic coating and form a protective layer in the scribe on AA2024-T3 under neutral salt spray conditions. The present paper shows the first observation and analysis of these corrosion protective layers, generated from lithium-salt loaded organic coatings. The scribed areas were examined by scanning and transmission electron microscopy before and after neutral salt spray exposure (ASTM-B117). The protective layers typically consist of three different layered regions, including a relatively dense layer near the alloy substrate, a porous middle layer and a flake-shaped outer layer, with lithium uniformly distributed throughout all three layers. Scanning electron microscopy and white light interferometry surface roughness measurements demonstrate that the formation of the layer occurs rapidly and, therefore provides an effective inhibition mechanism. Based on the observation of this work, a mechanism is proposed for the formation of these protective layers.

Properties Study of Mixed Silane Films on the Surface of Steel

2014 ◽  
Vol 971-973 ◽  
pp. 135-138
Author(s):  
Zhen Dong Sun ◽  
Yan Ning Yang ◽  
Qing Peng Li ◽  
Jian Guo Liu ◽  
Chuan Wei Yan
Keyword(s):  
Photoelectron Spectroscopy ◽  
Salt Spray ◽  
Adhesive Property ◽  
Epoxy Coating ◽  
Chemical Compositions ◽  
Neutral Salt ◽  
X Ray ◽  
Steel Sheets ◽  
Silane Solution ◽  
Scanning Electron

The mixed silane films were obtained on the surface of the Q235 steel sheets by directly immersing in a mixed silane solution containing γ-Glycidoxypropyltriethoxysilane (γ-GPS) and 1, 2-bis (triethoxysilyl) ethane (BTSE), The chemical compositions and microstructures of the films were examined by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier Transform infrared spectroscopy (FTIR).The corrosion resistances were investigated by electrochemical measurements and neutral salt spray (NSS) test. The effects of silane films to the epoxy coating were investigated through the adhesive property test. The results showed that the γ-GPS/BTSE mixed silane film could remarkably improve the corrosion resistance of epoxy coating and prolong its service life.

Structural Properties of Zinc and ZnMgAl Coatings on Steel Sheets

2014 ◽  
Vol 782 ◽  
pp. 623-626 ◽  
Author(s):  
Mária Kollárová ◽  
Lucia Hrabčáková ◽  
Juraj Graban ◽  
Marta Šohajová
Keyword(s):  
Corrosion Resistance ◽  
Salt Spray ◽  
Neutral Salt ◽  
Coating Structure ◽  
Properties Of Coatings ◽  
Steel Sheets ◽  
Mutual Comparison ◽  
Excellent Adhesion ◽  
Interdendritic Phase ◽  
Zinc Coatings

In the paper mutual comparison of zinc coatings enriched with small additions of Mg and Al (up to 1 wt.% Mg and 1 wt.% Al) and traditional zinc coatings produced by hot dip galvanizing, concerning some important properties of coatings like coating structure, cracks formation after deformation and corrosion resistance of deformed samples was studied. It was shown, that while traditional hot-dip zinc coatings are formed by homogenous zinc layer, exhibiting only low amount of soluble aluminium, coatings enriched by small amounts of Mg and Al, namely 0.6% Mg and 0.8% Al are formed by dendritic zinc matrix and interdendritic phase containing Zn-Mg-Al eutectics. Development of cracks was investigated in the area of maximal deformation of the samples subjected to stretching. It was found, that while traditional zinc coatings showed sporadic long fine cracks, zinc coatings enriched with Mg and Al exhibited aggregation of short thick cracks in the deformed area. Samples of both materials after stretching were also exposed in neutral salt spray atmosphere in corrosion chamber. It can be concluded, that material with coatings enriched with Mg and Al showed better results in corrosion tests contrary to the presence of massive cracks in the coating. This significantly increased corrosion resistance is possible due to excellent adhesion of zinc coatings, containing Mg and Al on drawing steels.

scholarly journals Effect of Inorganic Filler Addition on Non-Combustible and Mechanical Properties of Color Coated Steel Sheets

2020 ◽  
Vol 58 (11) ◽  
pp. 768-775
Author(s):  
Moon-Hi Hong ◽  
In-kyu Kim ◽  
Hye-Jeong Yun
Keyword(s):  
Mechanical Properties ◽  
Large Scale ◽  
Salt Spray ◽  
Galvanized Steel ◽  
Inorganic Filler ◽  
Coated Steel ◽  
Coating Materials ◽  
Steel Sheets ◽  
Glow Discharge Spectroscopy ◽  
Coated Layer

Recent large-scale fires in buildings and logistic warehouses have become a major social issue, involving both property loss and multiple casualties. To make color coated steel sheets non-combustible and/or have anti-fire properties, various ways of optimizing manufacturing parameters have been investigated for outer, inner, roof and ceiling panels. In the present study, the effect of inorganic filler content and size on the non-combustible and mechanical properties of color coated steel sheets has been investigated using samples prepared as pre-painted coating materials. Both salt spray corrosion and chemical resistance tests were also carried out. Filler distribution and size were measured by optical microscopy, scanning electron microscopy and glow discharge spectroscopy, and found to be critical factors affecting non-combustible performance. As the amount of added filler increased, the non-combustible property of the color coated steel sheets improved, while mechanical properties, corrosion resistance by salt spray and chemical resistances deteriorated. During 3t-bending tests, the adhesive strength at the interface between coated layer and hot dip galvanized steel sheets was rather strong, although the filler-added upper coated layer was mostly peeled off. The mechanical properties of 30% filler addition samples were compared to samples with less than 20% filler addition. The main reason for the poorer performance was clarified in terms of filler size and crack propagation in the 3t-bended color coated layer.

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