scholarly journals Structural Aspects of Decreasing the Corrosion Resistance of Zinc Coating Obtained in Baths with Al, Ni, and Pb Additives

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 385 ◽  
Author(s):  
Henryk Kania ◽  
Mariola Saternus ◽  
Jan Kudláček

The article presented the results of tests determining the synergistic effect of Al, Ni, and Pb additions on a zinc bath on the structure and corrosion resistance of coatings obtained on low silicon steel. Analyzed coatings were produced on S235JRG2 steel with Si content of 0.02 mass%. The corrosion resistance of the coatings was compared with the corrosion resistance of the coating obtained in the "pure" zinc bath. Structure at high magnifications (SEM) was determined, as well as coating thickness and chemical composition in microspheres. The corrosion resistance of the coatings was established comparatively in standard corrosion tests in neutral salt spray and a humid atmosphere containing SO2. It was found that the addition of Pb to the zinc bath reduced the corrosion resistance of the coatings. In the coating structure obtained in the Zn-AlNiPb bath, lead precipitation was observed in both the outer layer and the intermediate layer of the coating. Grain boundaries were the preferred site for lead precipitation. The presence of Pb precipitates favored conditions for the creation of additional corrosion cells, which led to a decrease in the corrosion resistance of the coatings.

Coatings ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 758
Author(s):  
Henryk Kania ◽  
Mariola Saternus ◽  
Jan Kudláček ◽  
Jakub Svoboda

The article examines the impact of the addition of Al, Ni, and Bi to a zinc bath on the microstructure and corrosion resistance of hot dip galvanizing coatings. The microstructure on the surface and the cross-section of the coatings obtained in the Zn-AlNiBi bath were examined. The corrosion resistance of the coatings was assessed by the standard neutral salt spray test (EN ISO 9227), the sulfur dioxide test in a humid atmosphere (EN ISO 6988), and the electrochemical test. The corrosion resistance of Zn-AlNiBi coatings was compared with the corrosion resistance of coatings attained in the bath of “pure” zinc. The corrosion tests showed higher corrosion wear of the coating obtained in the Zn-AlNiBi bath and a higher value of the corrosion current density for this coating. It was found that the cause of the reduction of the corrosion resistance of the coating, in contrast to the coating obtained in the “pure” zinc bath, may be the presence of bismuth precipitates in the coating, which may form additional corrosion cells.


2021 ◽  
Vol 1035 ◽  
pp. 545-553
Author(s):  
Yan Huang ◽  
Ren Bo Song ◽  
Huan Jun Wei ◽  
Zhe Rui Zhang ◽  
Li Fang Yang

The wear resistance and corrosion resistance of chromium-free fingerprint-resistant pure zinc and Zn-Al-Mg coated cold-rolled steel sheets were studied by micro-friction wear experiments and neutral salt spray experiments. Two products are worn for a long time with a large load (5N load, 50 times abrasion), the depth of wear zone of Zn-Al-Mg coating product is 9% shallower than that of pure zinc coating product, and the width of wear zone is 15.4% smaller. Both products still meet the requirements of use after corrosion. The corrosion resistance of two products after degreasing treatment was significantly reduced. The Mg and Al in the Zn-Al-Mg coating can hinder the progress of corrosion, so it has better corrosion resistance.


Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3788
Author(s):  
Henryk Kania ◽  
Mariola Saternus ◽  
Jan Kudláček

The paper presents results of studies on the impact of bismuth and tin additions to the Zn-AlNi bath on microstructure and corrosion resistance of hot dip galvanizig coatings. The structure at high magnifications on the top surface and cross-section of coatings received in the Zn-AlNiBiSn bath was revealed and the microanalysis EDS (energy dispersion spectroscopy) of chemical composition was determined. The corrosion resistance of the coatings was tested relatively in a neutral salt spray test (NSS), and tests in a humid atmosphere containing SO2. Electrochemical parameters of coatings corrosion were determined. It was found that Zn-AlNiBiSn coatings show lower corrosion resistance in comparison with the coatings received in the Zn-AlNi bath without Sn and Bi alloying additions. Structural research has shown the existence of precipitations of Sn-Bi alloy in the coating. It was found that Sn-Bi precipitations have more electropositive potential in relation to zinc, which promotes the formation of additional corrosion cells.


2014 ◽  
Vol 782 ◽  
pp. 623-626 ◽  
Author(s):  
Mária Kollárová ◽  
Lucia Hrabčáková ◽  
Juraj Graban ◽  
Marta Šohajová

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.


2016 ◽  
Vol 246 ◽  
pp. 85-90 ◽  
Author(s):  
Henryk Kania ◽  
Leszek Komorowski

In the paper the results of tests defining the influence of the chemical composition of a zinc bath on the corrosion resistance of coatings obtained on Sebisty steel are presented. The coatings for the tests were produced on Sebisty steel with the content of silicon of 0.18 wt. % in Zn-AlNi, Zn-AlNiPb and Zn-AlNiBiSn baths. Corrosion resistance of coatings obtained in alloy baths was compared with the corrosion resistance of a coating obtained in a bath of pure Zn. The structure of coatings has been developed, the chemical composition of structural components of the coating and the coating thickness have be established. Corrosion resistance of the coatings was defined by comparative methods in a standard corrosion test in neutral salt spray. The tests were carried out in accordance with the EN ISO 9227 standard. It has been established that alloy additions to a zinc bath have impact upon corrosion resistance of obtained coatings. The addition of Pb results in a decrease in corrosion resistance of a coating obtained on Sebisty steel.


2013 ◽  
Vol 212 ◽  
pp. 167-172 ◽  
Author(s):  
Henryk Kania ◽  
Marzena Bierońska

In the paper the authors present the results of corrosion resistance tests on coatings obtained in zinc-aluminium baths with the addition of Mg by use of the batch hot dip method. The content of Al in the bath was 31%, while the content of magnesium was 3 and 6%. In order to define corrosion resistance, two standard corrosion tests were performed in neutral salt spray and inmoist atmosphere containing sulphur dioxide. Corrosion resistance of tested pieces was compared with the corrosion resistance of a traditional zinc coating. It was established that Zn-31AlMg coatings have very good corrosion resistance in the tested environments, better than that of zinc coatings.


2016 ◽  
Vol 246 ◽  
pp. 99-104
Author(s):  
Mariola Saternus ◽  
Agnieszka Fornalczyk ◽  
Henryk Kania ◽  
Jacek Mendala

In the paper the results of corrosion resistance tests on ZnAlMg alloys used as batch hot dip galvanizing baths are presented. The tests were carried out on ZnAl alloys with 7 wt.% Al with the addition of 3 wt.% and 6 wt.% Mg. Corrosion resistance of tested alloys was compared with corrosion resistance of the traditional zinc bath alloy. Corrosion resistance of the alloys was defined by comparative methods in two standard corrosion tests in neutral salt spray and in moist atmosphere containing SO2. Electrochemical parameters of the corrosion process were determined on the basis of potentiodynamic tests. It was determined that the alloy of ZnAl7 has better corrosion resistance than the corrosion resistance of the alloy of a traditional zinc bath and that the addition of Mg to the alloy increases the corrosion resistance.


Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 337
Author(s):  
Ewa Wierzbicka ◽  
Marta Mohedano ◽  
Endzhe Matykina ◽  
Raul Arrabal

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.


Coatings ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 384
Author(s):  
Dariusz Ulbrich ◽  
Jakub Kowalczyk ◽  
Arkadiusz Stachowiak ◽  
Wojciech Sawczuk ◽  
Jaroslaw Selech

The article presents the influence of the applied method used for removing the varnish coat on the corrosion resistance of the car body sheet. The tests were carried out on samples prepared from factory-painted car body elements with pearlescent, metallized and acrylic varnish. Removal of the varnish coat was performed by sandpaper grinding, glass bead blasting, disc blaze rapid stripping, soda blasting and abrasive blasting with plastic granules. The average thickness of the factory-painted coating depending on the type of lacquer ranged from about 99 to 140 µm. On the other hand, after removing the varnish, the thickness of the protective zinc coating ranged from 2 to 12.7 µm. The highest values of the zinc coating were obtained for samples in which the varnish was removed by the method such as soda blasting and abrasive blasting with plastic granules. For these two methods of surface preparation, the damage to the zinc layer protecting the steel against corrosion is the smallest and the percentage of zinc in the surface layer ranges from 58% to 78%. The final stage of the research was to test the samples after removing the varnish coat in a two-hour exposure to the corrosive environment in a salt spray chamber. Samples with the surface prepared by grinding with sandpaper reached the level of surface rusting Ri 5, while in the case of soda blasting and the use of plastic granules, no corrosion centers were observed on the surface of the car body sheet.


Author(s):  
Jiří Votava

Metal components in engineering, industry and agriculture are subjects of degradation process influenced by corrosion which result in changes of mechanical characteristics. The current trend of anticorrosion protection is aimed at inorganic metal zinc-based coatings, such as zinc dipping which can be improved by duplex protection. This paper deals with two types of corrosion protection of steel components by zinc coating, first of which is produced by hot dip galvanizing, the other by Zn-Al spray. Hot dip galvanizing was processed in working conditions; the Zn-Al coating was sprayed following the instructions of producer. It is a special aerosol with particles of Zn and Al sized approximately 5 µm. There have been processed the following tests: analysis of element structure, test of corrosion resistance in aggressive environment of salt spray according to ČSN ISO 9227, further measurement weight of applied coatings according to ČSN EN ISO 3892 and measurement of thickness of passivating coating. There was also made an analysis of coating tenacity on bending pin according to ČSN EN ISO 8401. Quality of applied coatings was evaluated following the metallographic scratch pattern.


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