The Corrosion Resistance of Zn-Plated Samples with Blackish Green Passivation Film

2011 ◽  
Vol 383-390 ◽  
pp. 3081-3085
Author(s):  
Yu Bao Cao
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Sample Surface ◽  
Corrosion Current ◽  
Electrochemical Process ◽  
Salt Spray Test ◽  
Neutral Salt ◽  
Passivation Film ◽  
Passivated Sample

The corrosion resistance of blackishgreen passivation films on zinc-plated steel sheet was studied by polarization curve measurement, electrochemical impedance spectroscopy and neutral salt spray test. The passivated sample featured a more positive corrosion potential and much lower corrosion current density as compared to non-passivated sample in 5% (mass fraction) NaCl solution. The Nyquist plots of the samples with and without passivation were characterized as two complete capacitive arcs, indicating that the corrosion is controlled by electrochemical process. The radii of capacitive arcs of the passivated sample are larger than those of non-passivated sample, because the passivation film formed on the sample surface increases the reaction resistance in corrosion process, thus the corrosion resistance of the sample is improved. The anti-white rust time of the passivation film in neutral salt spray test is 400 h.

scholarly journals Design and Multidimensional Screening of Flash-PEO Coatings for Mg in Comparison to Commercial Chromium(VI) Conversion Coating

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 337
Author(s):  
Ewa Wierzbicka ◽  
Marta Mohedano ◽  
Endzhe Matykina ◽  
Raul Arrabal
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Protection ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Conversion Coating ◽  
Neutral Salt ◽  
Chromium Vi ◽  
Alkaline Electrolytes ◽  
Az31b Alloy ◽  
Plasma Electrolytic

REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) regulations demand for an expedient discovery of a Cr(VI)-free alternative corrosion protection for light alloys even though the green alternatives might never be as cheap as current harmful technologies. In the present work, flash- plasma electrolytic oxidation coatings (FPEO) with the process duration < 90 s are developed on AZ31B alloy in varied mixtures of silicate-, phosphate-, aluminate-, and fluoride-based alkaline electrolytes implementing current density and voltage limits. The overall evaluation of the coatings’ anticorrosion performance (electrochemical impedance spectroscopy (EIS), neutral salt spray test (NSST), paintability) shows that from nine optimized FPEO recipes, two (based on phosphate, fluoride, and aluminate or silicate mixtures) are found to be an adequate substitute for commercially used Cr(VI)-based conversion coating (CCC). The FPEO coatings with the best corrosion resistance consume a very low amount of energy (~1 kW h m−2 µm−1). It is also found that the lower the energy consumption of the FPEO process, the better the corrosion resistance of the resultant coating. The superb corrosion protection and a solid environmentally friendly outlook of PEO-based corrosion protection technology may facilitate the economic justification for industrial end-users of the current-consuming process as a replacement of the electroless CCC process.

Corrosion resistance of composite coating used for fastener protection

2019 ◽  
Vol 66 (5) ◽  
pp. 595-602
Author(s):  
Zhifeng Lin ◽  
Likun Xu ◽  
Xiangbo Li ◽  
Li Wang ◽  
Weimin Guo ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Carbon Steel ◽  
Composite Coating ◽  
Marine Environment ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Diffusion Method ◽  
Economic Losses ◽  
Neutral Salt ◽  
Content Type

Purpose The purpose of this paper is to examine the performance of a fastener composite coating system, sherardized (SD) coating/zinc-aluminum (ZA) coating whether it has good performance in marine environment. Design/methodology/approach In this paper, SD coating was fabricated on fastener surface by solid-diffusion method. ZA coating was fabricated by thermal sintering method. Corrosion behaviours of the composite coating were investigated with potentiodynamic polarization curves, open circuit potential and electrochemical impedance spectroscopy methods. Findings Neutral salt spray (NSS) and deep sea exposure tests revealed that the composite coating had excellent corrosion resistance. Polarization curve tests showed that corrosion current density of the sample with composite coating was significantly decreased, indicating an effective corrosion protection of the composite coating. OCP measurement of the sample in NaCl solution demonstrated that the composite coating had the best cathodic protection effect. The good corrosion resistance of the composite coating was obtained by the synergy of SD and ZA coating. Practical implications SD/ZA coating can be used in marine environment to prolong the life of carbon steel fastener. Social implications SD/ZA composite coating can reduce the risk and accident caused by failed fastener, avoid huge economic losses. Originality/value A new kind of composite coating was explored to protect the carbon steel fastener in marine environment. And the composite coating has the long-term anti-corrosion performance both in simulated and marine environment test.

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%.

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.

scholarly journals Ultrasonic Sensors-Assisted Corrosion Studies on Surface Coated AlSi9Cu3 Alloy Die Castings

Coatings ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 85
Author(s):  
Yuh-Chung Hu ◽  
Senthil Kumaran Selvaraj ◽  
Manivannan Subramanian ◽  
Kathiravan Srinivasan ◽  
Srinivasan Narayanan
Keyword(s):  
Corrosion Resistance ◽  
Die Casting ◽  
Pure Aluminum ◽  
Salt Spray ◽  
Salt Spray Test ◽  
Al Alloy ◽  
Neutral Salt ◽  
Powder Coatings ◽  
Acrylic Paint ◽  
Epoxy Primer

A novel phenomenon known as Industry X.0 is becoming extremely popular for digitizing and reinventing business organizations through the adaption of rapid and dynamic technological, innovational, and organizational changes for attaining the profitable revenue. This work investigates the die-casted commercially pure aluminum alloyed with 9% silicon and 3% copper (AlSi9Cu3) that is produced through the gravity die casting process. Further, the degradation of surface coating on die-casted AlSi9Cu3 alloy was explored. The acrylic paint electrodeposition (ED) coat, 2-coat polyester without primer and 3-coat polyester with epoxy primer powder coatings were used in this study. Moreover, the 3.5 wt.% of sodium chloride (3.5 wt.% of NaCl) test solution was used for electrochemical and salt spray test and the tools used to assess electrochemical properties were electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and neutral salt spray test (NSS). The microstructure of AlSi9Cu3 after corrosion exposure was investigated; also, the microstructure of coated and uncoated AlSi9Cu3 samples was analyzed by SEM microscopy after corrosion exposure. Besides, the electrochemical studies were also carried out on the Al alloy die casting. It was found that acrylic paint ED coatings exhibited higher corrosion resistance than 2-coat polyester without primer & 3-coat polyester with epoxy primer powder coatings. Acrylic paint ED coating showed higher corrosion resistance in AC and a lower value in DC and 3-coat polyester with epoxy primer powder coating displayed higher corrosion resistance in DC and a lower value in AC.

scholarly journals Improvement of AZ91 Alloy Corrosion Properties by Duplex NI-P Coating Deposition

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1357 ◽  
Author(s):  
Jaromír Wasserbauer ◽  
Martin Buchtík ◽  
Jakub Tkacz ◽  
Stanislava Fintová ◽  
Jozef Minda ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Az91 Alloy ◽  
Neutral Salt ◽  
Az91 Magnesium Alloy ◽  
Corrosion Properties ◽  
Az91 Magnesium

The corrosion behavior of duplex Ni-P coatings deposited on AZ91 magnesium alloy was studied. The electroless deposition process of duplex Ni-P coating consisted in the preparation of low-phosphorus Ni-P coating (5.7 wt.% of P), which served as a bond coating and high-phosphorus Ni-P coating (11.5 wt.% of P) deposited on it. The duplex Ni-P coatings with the thickness of 25, 50, 75 and 100 µm were deposited on AZ91 magnesium alloy. The electrochemical corrosion behavior of coated AZ91 magnesium alloy was investigated by electrochemical impedance spectroscopy and potentiodynamic polarization method in 0.1 M NaCl. Obtained results showed a significant improvement in the corrosion resistance of coated specimens when compared to uncoated AZ91 magnesium alloy. From the results of the immersion tests in 3.5 wt.% NaCl, 10% solution of HCl and NaOH and 5% neutral salt spray, a noticeable increase in the corrosion resistance with the increasing thickness of the Ni-P coating was observed.

Passivation Effect of Rare Earth Lanthanum on Galvanized Steel

2014 ◽  
Vol 525 ◽  
pp. 31-34
Author(s):  
Xiao Feng Liu
Keyword(s):  
Corrosion Resistance ◽  
Rare Earth ◽  
Electrochemical Impedance ◽  
Orthogonal Experiment ◽  
Salt Spray ◽  
Conversion Coating ◽  
Galvanized Steel ◽  
Neutral Salt ◽  
White Rust ◽  
Order Of Magnitude

By way of chemical marinate method, carrying out rare earth lanthanum to corrosion protect galvanized steel. The process of rare earth lanthanum conversion coating for galvanized steel was studied by using orthogonal experiment to get the optimized passivation parameters when the concentration of La (NO3) is 30g/L, H2O2is 20ml/L, pH=4 and was passivated at 40°C for 30s. The corrosion resistance was examined by weight loss tests, neutral salt spray tests (NSS) and electrochemical impedance spectroscopy (EIS). The results showed that the corrosion impedance of the pretreated sample was significantly improved, the corrosion rate was decreased by one order of magnitude, and the anti-white rust time was 54h.

scholarly journals Comparative Study on the Corrosion Resistance of 6061Al and SiC3D/6061Al Composite in a Chloride Environment

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7730
Author(s):  
Liang Yu ◽  
Shuangshuang Hao ◽  
Xiaodong Nong ◽  
Xiuling Cao ◽  
Chen Zhang ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Specific Area ◽  
Open Circuit ◽  
Pressure Casting ◽  
Neutral Salt ◽  
Salt Leaching ◽  
Chloride Environment ◽  
Al Matrix

Interface problems and the destruction of the continuity of the oxide film in the Al matrix usually reduce the corrosion resistance of the material. In this paper, the corrosion resistance of Al matrix composites (AMCs) was improved by introducing the silicon carbide skeletons (SiC3D) obtained with polymer replica technology. SiC3D/6061Al was fabricated by infiltrating molten 6061Al alloy in the oxidized SiC3D using the low-pressure casting method. The corrosion resistance performances of 6061Al and SiC3D/6061Al in NaCl solution were studied by electrochemical, neutral salt spray corrosion (NSS), and salt leaching (SL) tests. Results show corrosion resistance of SiC3D/6061Al is higher than that of 6061Al alloys by open circuit potential (OCP), potentio-dynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) tests. However, NSS and SL tests show the corrosion resistance of SiC3D/6061Al is lower than that of 6061Al alloy. The reason is a corrosion resistant and anti-oxidation network macrostructure with large interface recombination, few concentrated interfaces, and a small specific area that formed in SiC3D/6061Al. SiC3D cannot damage the continuity of the Al2O3 passivating film, and the network macrostructure greatly improves the corrosion resistance performance.

Fabrication and Corrosion Properties of Electroplated Ni-Co-Cr Alloy Coatings

2013 ◽  
Vol 456 ◽  
pp. 438-441 ◽  
Author(s):  
Tian Yang ◽  
Cheng Zhang Peng ◽  
Lang Xiang ◽  
Huo Cao
Keyword(s):  
Corrosion Resistance ◽  
Salt Spray ◽  
Low Carbon Steel ◽  
Corrosion Current ◽  
Polarization Measurement ◽  
Neutral Salt ◽  
Low Carbon ◽  
X Ray Diffraction ◽  
Corrosion Properties ◽  
X Ray

The electroplated Ni-Co-Cr coatings were prepared on surface of a low carbon steel. The microstructure of the deposits were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD), the corrosion resistance of the deposits was evaluated using neutral salt-spray test and polarization measurement. The results show that the deposits are a Co and Cr solid solution in Ni with a grain size of 6.9~10.6nm, were nearly free of corrosion after neutral salt-spray tested 100 hours. With chromium content increasing, the coatings exhibited higher corrosion potential and lower corrosion current, which revealed excellent corrosion resistance.

Electrochemical Characteristics of an Optimized Ni-P-Zn Electroless Composite Coating

2014 ◽  
Vol 1043 ◽  
pp. 124-128 ◽  
Author(s):  
Amir Kordijazi
Keyword(s):  
Corrosion Resistance ◽  
Composite Coating ◽  
Electrochemical Impedance ◽  
Salt Spray ◽  
Corrosion Current ◽  
Electrochemical Characteristics ◽  
High Corrosion ◽  
Excellent Corrosion Resistance ◽  
Coating Composition ◽  
Spray Technique

An optimized electroless solution was used to deposit the Ni-P-Zn composite coating. Potentiodynamic polarization test, salt spray technique and electrochemical impedance spectroscopy were utilized to study electrochemical characteristics of the as-deposited coating. All results demonstrate an excellent corrosion resistance of the as-deposited layer. Corrosion current density of the coating was compared to some similar coatings reported in other papers to study reasons of its high corrosion resistance. It was proved that the high corrosion protection of the coating is due to the optimization of P and Zn contents in the coating composition.

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