Corrosion Behavior Of Zinc Coatings Research Articles

Characterization and Corrosion Behavior of Zinc Coatings for Two Anti-Corrosive Protections: A Detailed Study

The purpose of this research is to characterize and evaluate the corrosion behavior of zinc coatings used for corrosion protection, with a special focus on the S235 steel material. The introduction highlights the need for corrosion protection in industrial settings, as well as the importance of understanding corrosion processes and the development of corrosion products to develop more effective solutions. The study’s goals are to undertake an extensive analysis of corrosion products formed on the zinc coating’s surface, to evaluate the performance of these coatings under atmospheric circumstances, and to investigate the effect of deposition parameters on coating quality. The essential message provided to readers is the critical significance of knowing corrosion product formation mechanisms and zinc coating corrosion behavior in developing long-lasting and effective protection measures. The study methodology includes cycle testing, morphological and chemical examination of corrosion products, as well as optical and electron microscopy and energy-dispersive spectroscopy. Corrosion resistance is assessed using accurate measurements. The results show that zinc coatings have exceptional corrosion resistance under air settings, with the produced corrosion products offering further protection to the underlying material. Furthermore, the study demonstrates that the surface roughness of S235 steel has a substantial impact on the quality and corrosion behavior of hot-dip galvanized coatings. The findings emphasize the necessity of detailed characterization of corrosion products, the effect of depositional factors on zinc coating performance, and the need for novel corrosion protection methods. These discoveries have significant implications for the corrosion protection sector, providing the potential to improve the longevity and efficiency of protective systems used in industrial applications.

Efecto de la composición química del baño en la microestructura y resistencia a la corrosión de los recubrimientos de zinc por inmersión en caliente: Una revisión

Los recubrimientos metálicos son métodos ampliamente utilizados para la protección contra la corrosión de aleaciones metálicas, siendo el proceso de cincado por inmersión en caliente uno de los que presenta mayor evolución a nivel industrial. El objetivo de este trabajo es realizar una revisión bibliográfica sobre la influencia de la adición de elementos aleantes en el baño, en la microestructura y en el comportamiento a la corrosión de recubrimientos de zinc obtenidos por la técnica de inmersión en caliente. Se estableció que la composición química de los baños galvanizados influye en las características microestructurales de los recubrimientos y en su comportamiento a la corrosión. La mejora de la resistencia a la corrosión de los recubrimientos de zinc se produce por la adición a los baños de elementos generalmente más activos que el zinc, tales como el magnesio o el aluminio que permiten la formación de capas pasivas que retardan el proceso corrosivo.

An Appropriate Specimen Configuration for Evaluating the Perforation Corrosion Resistance of Automotive Coated Steel Sheets in Accelerated Corrosion Tests

A variety of metallic coatings have been developed for automotive steel sheet panels to achieve better corrosion resistance. Accelerated corrosion tests are used to develop and select coated steel sheets in a short period. In addition to the test conditions, a specimen configuration simulating the lapped portion of vehicles is another important issue when evaluating resistance to perforation corrosion in the laboratory since the specimen must reproduce the unique environment inside the lapped portion. In this study, lapped specimens with different configurations were prepared and the influence of a bare area in a large crevice on the corrosion behavior of zinc coatings was systematically analyzed by comparing the results of laboratory tests with the corrosion observed in vehicles in service. It was found that the controlling factor of resistance to perforation corrosion was influenced by the configuration of the test specimen. A large crevice gap and bare area in the crevice of the lapped portion changed ...

Behavior of Electrogalvanized Steel Pre-Treated with Cr(III)-Based Baths and Exposed to 0.5 M Na2SO4 Solution

As Cr (VI) compounds used to formulate conversion layers provide enhanced anticorrosive protection to zinc coatings, but they are produced using hazardous chemicals, the development of “green” technologies is a paramount purpose. Consequently, the corrosion behavior of zinc coatings subjected to a Cr 3+ based passivating treatment, with and without sealing, was studied through EIS measurements in 0.5 M Na 2SO 4 solution. The analyses of the experimental data allowed inferring that the Cr 3+ -based conversion treatment with an adequate sealer provides good corrosion resistance and, coupled to an adequate painting system, could be a suitable alternative to traditional chromate coatings .

Corrosion resistance of Cr(III) conversion treatments applied on electrogalvanised steel and subjected to chloride containing media

The corrosion resistance of pure zinc coatings can be improved through the application of suitable chemical passivation treatments. Hexavalent chromium compounds have widely been used to formulate conversion layers providing better anticorrosive protection as well as anchorage properties to painting systems. However, taking into account that they are produced using hazardous chemical compounds, the development of alternative and “green” technologies with equivalent protective performance is a paramount purpose of many R&D laboratories working around the world. In the present paper, the corrosion behavior of zinc coatings obtained from free-cyanide alkaline baths and later subjected to a Cr 3+ based passivation treatment, with and without a sealing treatment, was studied. The experimental work involved electrochemical impedance spectroscopy measurements in 0.5 M NaCl solution, surface microstructural and morphological characterization by electronic microscopy as well as chemical analysis by EDXS. The salt spray test was also performed. The analysis and interpretation of all the data coming from this battery of tests allowed inferring that both the Cr 3+ based conversion treatment + adequate sealer presented a good corrosion resistance and, therefore, they could be used as neither a polluting nor toxic alternative to the traditional chromate coatings.

Comparative study of the corrosion behavior of zinc coatings deposited on low carbon steel substrates

AbstractThe corrosion behavior of zinc pack coatings was examined with X‐ray diffraction (XRD) and scanning electron microscopy (SEM) and it was compared with the performance of the zinc coatings formed with hot dipping. The examined samples were exposed in a salt spray chamber (SSC) for different periods of time starting from 24 h up to ten days. This investigation showed that the main corrosion products were Zn‐ and Fe‐hydrated chlorides and oxides, while a stress corrosion mechanism controlled the pack corrosion. By contrast, the hot‐dipped coatings are uniformly corroded, while pitting corrosion and internal oxidation are also possible. Copyright © 2006 John Wiley & Sons, Ltd.

A comparative study of the structure and the corrosion behavior of zinc coatings deposited with various methods

The structure and the corrosion performance of Zn coatings formed by pack cementation and fluidized bed reactor at 250, 350, 380 and 400 °C have been studied. From this investigation, it turned out that these coatings are composed of two layers referring to γ-Fe 11Zn 40 and δ-FeZn 10 phases of the Fe–Zn phase diagram. Furthermore, in the pack coatings, inclusions were detected, which are composed of Fe and Zn at almost equal concentrations. Concerning the corrosion, a mechanism of stress corrosion has been identified. The corrosion performance of the studied coatings is similar to that of the hot-dip galvanized coatings, although the deposition method is different.

Role of Buffering and Complexing Agents in Zinc Plating Chloride Baths on Corrosion Resistance of Produced Coatings

Corrosion behavior of zinc coatings produced from ammonium chloride + zinc chloride + potassium chloride bath (ACB) and zinc chloride + potassium chloride + boric acid bath (BAB) was studied using weight-loss and electrochemical techniques. It was established that the zinc coatings electrodeposited in ACB performs better than the electrodeposited coatings produced from BAB. The zinc deposition reactions in baths having ammonium chloride polarized to a greater extent than the bath blended with boric acid. Alternating current (AC) impedance studies demonstrated that the coatings produced in both types of solutions formed unstable film in corrosive media. This was corroborated by weight-loss as well as direct current (DC) polarization techniques. The presence of boric acid in the plating bath had little influence on charge-transfer resistance of zinc deposition. However, the electrochemical double-layer capacitance decreased with the increase of boric acid concentration in the bath. Scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) studies revealed that the coating produced in ACB has amorphous-type grains whereas the BAB coating showed a crystalline structure. It was concluded that improved corrosion resistance of the zinc coating deposited in the ACB was caused by the stronger complexing tendency of ammonium chloride with zinc cations, which resulted in a slow discharge of this ion during the deposition process.