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2 pages, 155 KiB

Open AccessEditorial

Development of Mechanical, Corrosion Resistance, and Antibacterial Properties of Steels

by Marjetka Conradi

Materials 2021, 14(24), 7698; https://doi.org/10.3390/ma14247698 - 13 Dec 2021

Cited by 1 | Viewed by 1273

Abstract

The total cost and environmental consequences of corrosion problems have become a major challenge to engineers [...] Full article

(This article belongs to the Special Issue Development of Mechanical, Corrosion Resistance, and Antibacterial Properties of Steels)

Research

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13 pages, 6748 KiB

Open AccessEditor’s ChoiceArticle

Improvement of Corrosion Resistance of TiO₂ Layers in Strong Acidic Solutions by Anodizing and Thermal Oxidation Treatment

by Badar Minhas, Sahib Dino, Yu Zuo, Hongchang Qian and Xuhui Zhao

Materials 2021, 14(5), 1188; https://doi.org/10.3390/ma14051188 - 03 Mar 2021

Cited by 8 | Viewed by 2788

Abstract

By anodization and thermal oxidation at 600 °C, an oxide layer on Ti with excellent corrosion resistance in strong acid solutions was prepared. The structural properties of TiO₂ films before and after thermal oxidation were investigated with methods of Scanning electron microscope [...] Read more.

By anodization and thermal oxidation at 600 °C, an oxide layer on Ti with excellent corrosion resistance in strong acid solutions was prepared. The structural properties of TiO₂ films before and after thermal oxidation were investigated with methods of Scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The electrochemical characterization was recorded via electrochemical impedance spectroscopy, potentiodynamic polarization and Mott–Schottky methods. XRD results show that a duplex rutile/anatase structure formed after oxidation, and the amount of anatase phase increased as the treatment time was prolonged from 3 to 9 h. XPS analysis indicates that as the thermal oxidation time increased, more Ti vacancies were present in the titanium oxide films, with decreased donor concentration. Longer thermal oxidation promoted the formation of hydroxides of titanium on the surface, which is helpful to improve the passive ability of the film. The anodized and thermally oxidized Ti samples showed relatively high corrosion resistance in 4 M HCl and 4 M H₂SO₄ solutions at 100 ± 5 °C. The passive current density values of the thermally oxidized samples were five orders of magnitude under the testing condition compared with that of the anodized sample. With the oxidation time prolonged, the passive current density decreased further to some extent. Full article

(This article belongs to the Special Issue Development of Mechanical, Corrosion Resistance, and Antibacterial Properties of Steels)

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16 pages, 2757 KiB

Open AccessArticle

Influence of the Interlayer Temperature on Structure and Properties of Wire and Arc Additive Manufactured Duplex Stainless Steel Product

by Nikola Knezović, Ivica Garašić and Ivan Jurić

Materials 2020, 13(24), 5795; https://doi.org/10.3390/ma13245795 - 18 Dec 2020

Cited by 18 | Viewed by 2829

Abstract

WAAM (wire and arc additive manufacturing) is becoming an increasingly popular method to produce components from metals, which are usually not so suitable for conventional production methods. One of the good examples is duplex stainless steels (DSSs), which are quite complex for welding [...] Read more.

WAAM (wire and arc additive manufacturing) is becoming an increasingly popular method to produce components from metals, which are usually not so suitable for conventional production methods. One of the good examples is duplex stainless steels (DSSs), which are quite complex for welding and machining. Excessive ferrite amount is a common problem for them and controlling an interlayer temperature could offer a solution. However, using too low interlayer temperature will slow down the whole process and compromise one of the WAAM’s main advantages—the high productivity. The aim of this study is to find the relationship between interlayer temperature and process duration and to determine the influence of the interlayer temperature on product structure and other properties. Three samples (walls) were made using different interlayer temperatures (50 °C, 100 °C and 150 °C) and they were tested to analyze their surface texture, chemical composition, ferrite amount, the appearance of porosity and the hardness. Ferrite amount was higher and there was more porosity on lower interlayer temperatures, while there is no significant difference between surface texture and chemical composition for the samples. Considering the fact that higher interlayer temperatures provide a faster process, they should be preferred to produce duplex stainless steel products. Full article

(This article belongs to the Special Issue Development of Mechanical, Corrosion Resistance, and Antibacterial Properties of Steels)

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17 pages, 2372 KiB

Open AccessArticle

Progressive Applications of Hyperbranched Polymer Based on Diarylamine: Antimicrobial, Anti-Biofilm and Anti-Aerobic Corrosion

by Khalid I. Kabel, Ahmed Labena, Mohamed Keshawy and Wael N. Hozzein

Materials 2020, 13(9), 2076; https://doi.org/10.3390/ma13092076 - 30 Apr 2020

Cited by 7 | Viewed by 2062

Abstract

New generations of hyperbranched aramids were synthesized from diarylamine and methyl acrylate using an AB₂ monomer approach in a straightforward one-pot preparation. The chemical structure of hyperbranched Phenylenediamine/Methyl Acrylate HB(PDMA was confirmed by Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance ( [...] Read more.

New generations of hyperbranched aramids were synthesized from diarylamine and methyl acrylate using an AB₂ monomer approach in a straightforward one-pot preparation. The chemical structure of hyperbranched Phenylenediamine/Methyl Acrylate HB(PDMA was confirmed by Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (¹HNMR) spectroscopy. In addition, the particle’s size and distribution were recorded using Dynamic Light Scattering (DLS). Moreover, the synthesized HB(PDMA)s displayed broad-spectrum antimicrobial activities against Gram-positive and Gram-negative bacteria as well as yeast strains and anti-biofilm activity where the highest activity was attributed to HB(PDMA)G₄ at the lowest Minimum Inhibitory, Minimum Bactericidal, and Fungicidal Concentrations (MIC, MBC, and MFC, respectively). Furthermore, the HB(PDMA)s expressed anti-bacterial activity against isolated Pseudomonas sp. (R301) at a salinity of 35,000 ppm (NaCl). In addition, they revealed different corrosion inhibition efficiencies at the cultivated medium salinity at the estimated minimum bactericidal concentrations. The highest metal corrosion inhibition efficiencies were 59.5 and 94.3% for HB(PDMA)G₄ at the Minimum Bactericidal Concentrations (MBCs) and two times Minimum Bactericidal Concentrations (2XMBCs), respectively, in comparison to both negative and positive controls. Full article

(This article belongs to the Special Issue Development of Mechanical, Corrosion Resistance, and Antibacterial Properties of Steels)

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10 pages, 2381 KiB

Open AccessArticle

Manipulation of TiO₂ Nanoparticle/Polymer Coatings Wettability and Friction in Different Environments

by Marjetka Conradi, Aleksandra Kocijan, Tadeja Kosec and Bojan Podgornik

Materials 2020, 13(7), 1702; https://doi.org/10.3390/ma13071702 - 05 Apr 2020

Cited by 8 | Viewed by 1906

Abstract

An AISI 316L surface was functionalized by the adsorption of hydrophilic epoxy and epoxy/TiO₂/epoxy coatings and hydrophobic epoxy/fluoroalkylsilane-functionalized FAS-TiO₂/epoxy coatings. We characterized the coatings’ wettability, morphology and average surface roughness and discussed the influence of surface wettability and morphology [...] Read more.

An AISI 316L surface was functionalized by the adsorption of hydrophilic epoxy and epoxy/TiO₂/epoxy coatings and hydrophobic epoxy/fluoroalkylsilane-functionalized FAS-TiO₂/epoxy coatings. We characterized the coatings’ wettability, morphology and average surface roughness and discussed the influence of surface wettability and morphology on the coefficient of friction and the wear resistance. Experiments were performed in dry, distilled water and in a simulated physiological solution (Hank’s solution). In the case of dry sliding, a lower coefficient of friction is achieved for both TiO₂ coatings compared to the pure epoxy coating. In a water environment the same level of friction is shown for all three coatings, whereas in Hank’s solution the friction is reduced for the hydrophilic epoxy/TiO₂/epoxy coating, increased for the hydrophobic epoxy/FAS-TiO₂/epoxy coating and has no effect on the pure epoxy coating. The results show that the corrosion resistance is significantly improved for the hydrophobic epoxy/FAS-TiO₂/epoxy coating compared to the hydrophilic pure epoxy and epoxy/TiO₂/epoxy coatings. Full article

(This article belongs to the Special Issue Development of Mechanical, Corrosion Resistance, and Antibacterial Properties of Steels)

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16 pages, 4516 KiB

Open AccessFeature PaperArticle

Monitoring the Corrosion of Steel in Concrete Exposed to a Marine Environment

by Nina Gartner, Tadeja Kosec and Andraž Legat

Materials 2020, 13(2), 407; https://doi.org/10.3390/ma13020407 - 15 Jan 2020

Cited by 27 | Viewed by 3724

Abstract

Reinforced concrete structures require continuous monitoring and maintenance to prevent corrosion of the carbon steel reinforcement. In this work, concrete columns with carbon and stainless steel reinforcements were exposed to a real marine environment. In order to monitor the corrosion processes, two types [...] Read more.

Reinforced concrete structures require continuous monitoring and maintenance to prevent corrosion of the carbon steel reinforcement. In this work, concrete columns with carbon and stainless steel reinforcements were exposed to a real marine environment. In order to monitor the corrosion processes, two types of corrosion probes were embedded in these columns at different height levels. The results from the monitoring of the probes were compared to the actual corrosion damage in the different exposure zones. Electrical resistance (ER) probes and coupled multi-electrodes (CMEs) were shown to be promising methods for long-term corrosion monitoring in concrete. Correlations between the different exposure zones and the corrosion processes of the steel in the concrete were found. Macrocell corrosion properties and the distribution of the separated anodic/cathodic places on the steel in chloride-contaminated concrete were addressed as two of the key issues for understanding the corrosion mechanisms in such environments. The specific advantages and limitations of the tested measuring techniques for long-term corrosion monitoring were also indicated. The results of the measurements and the corrosion damage evaluation clearly confirmed that the tested stainless steels (AISI 304 and AISI 304L) in a chloride-contaminated environment behave significantly better than ordinary carbon steel, with corrosion rates from 110× to 9500× lower in the most severe (tidal) exposure conditions. Full article

(This article belongs to the Special Issue Development of Mechanical, Corrosion Resistance, and Antibacterial Properties of Steels)

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11 pages, 4563 KiB

Open AccessArticle

Activation and Repassivation of Stainless Steels in Artificial Brines as a Function of pH

by Emir Mujanović, Bojan Zajec, Tadeja Kosec, Andraž Legat, Stefan Hönig, Gerald Zehethofer and Gregor Mori

Materials 2019, 12(23), 3811; https://doi.org/10.3390/ma12233811 - 20 Nov 2019

Cited by 4 | Viewed by 2339

Abstract

When planning oil wells with stainless steel components, two possible reasons for depassivation have to be considered—chemical depassivation caused by acidizing jobs and mechanical depassivation caused by various tools and hard particles. The study explores conditions causing chemical activation of investigated steels and [...] Read more.

When planning oil wells with stainless steel components, two possible reasons for depassivation have to be considered—chemical depassivation caused by acidizing jobs and mechanical depassivation caused by various tools and hard particles. The study explores conditions causing chemical activation of investigated steels and circumstances under which repassivation occurs after activation. The main focus of the study is to determine, how quickly various steels can repassivate under different conditions and to find pH values where repassivation will occur after depassivation. The investigated steels were ferritic (martensitic or bainitic) in the cases of 13Cr, 13Cr6Ni2Mo, and 17Cr4Ni2Mo, austenitic in the case of 17Cr12Ni2Mo, and duplex (austenitic and ferritic) in the case of 22Cr5Ni3Mo. Potentiodynamic experiments were employed to obtain electrochemical properties of investigated steels, followed by immersion tests to find ultimate conditions, where the steels still retain their passivity. After obtaining this information, scratch tests were performed to study the repassivation kinetics. It was found that repassivation times are similar for nearly all investigated steels independent of their chemical composition and microstructure. Full article

(This article belongs to the Special Issue Development of Mechanical, Corrosion Resistance, and Antibacterial Properties of Steels)

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11 pages, 4001 KiB

Open AccessArticle

The Influence of Surface Wettability and Topography on the Bioactivity of TiO₂/Epoxy Coatings on AISI 316L Stainless Steel

by Aleksandra Kocijan, Marjetka Conradi and Matej Hočevar

Materials 2019, 12(11), 1877; https://doi.org/10.3390/ma12111877 - 11 Jun 2019

Cited by 33 | Viewed by 3656

Abstract

Epoxy/TiO₂/epoxy and epoxy/FAS-TiO₂/epoxy coatings were applied to the surface of AISI 316L stainless steel with the aim to improve the biocompatibility and antibacterial properties. Contact-angle measurements were used to evaluate the wetting properties of the epoxy, epoxy/TiO₂/epoxy [...] Read more.

Epoxy/TiO₂/epoxy and epoxy/FAS-TiO₂/epoxy coatings were applied to the surface of AISI 316L stainless steel with the aim to improve the biocompatibility and antibacterial properties. Contact-angle measurements were used to evaluate the wetting properties of the epoxy, epoxy/TiO₂/epoxy and epoxy/FAS-TiO₂/epoxy coatings. The epoxy and epoxy/TiO₂/epoxy coatings were hydrophilic compared with the strongly hydrophobic epoxy/FAS-TiO₂/epoxy coating. The average surface roughness (S_a) of the epoxy/FAS-TiO₂/epoxy coating was higher than that of the epoxy/TiO₂/epoxy coating due to the formation of agglomerates. The biocompatibility evaluation revealed that the cell attachment was significantly higher on the epoxy/FAS-TiO₂/epoxy and epoxy/TiO₂/epoxy coatings compared with the pure epoxy coating. We also observed improved antibacterial properties for the epoxy coatings with the addition of both TiO₂ and FAS-TiO₂ nanoparticles. Full article

(This article belongs to the Special Issue Development of Mechanical, Corrosion Resistance, and Antibacterial Properties of Steels)

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Review

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22 pages, 4403 KiB

Open AccessReview

Strategies for Improving Antimicrobial Properties of Stainless Steel

by Matic Resnik, Metka Benčina, Eva Levičnik, Niharika Rawat, Aleš Iglič and Ita Junkar

Materials 2020, 13(13), 2944; https://doi.org/10.3390/ma13132944 - 30 Jun 2020

Cited by 30 | Viewed by 5168

Abstract

In this review, strategies for improving the antimicrobial properties of stainless steel (SS) are presented. The main focus given is to present current strategies for surface modification of SS, which alter surface characteristics in terms of surface chemistry, topography and wettability/surface charge, without [...] Read more.

In this review, strategies for improving the antimicrobial properties of stainless steel (SS) are presented. The main focus given is to present current strategies for surface modification of SS, which alter surface characteristics in terms of surface chemistry, topography and wettability/surface charge, without influencing the bulk attributes of the material. As SS exhibits excellent mechanical properties and satisfactory biocompatibility, it is one of the most frequently used materials in medical applications. It is widely used as a material for fabricating orthopedic prosthesis, cardiovascular stents/valves and recently also for three dimensional (3D) printing of custom made implants. Despite its good mechanical properties, SS lacks desired biofunctionality, which makes it prone to bacterial adhesion and biofilm formation. Due to increased resistance of bacteria to antibiotics, it is imperative to achieve antibacterial properties of implants. Thus, many different approaches were proposed and are discussed herein. Emphasis is given on novel approaches based on treatment with highly reactive plasma, which may alter SS topography, chemistry and wettability under appropriate treatment conditions. This review aims to present and critically discuss different approaches and propose novel possibilities for surface modification of SS by using highly reactive gaseous plasma in order to obtain a desired biological response. Full article

(This article belongs to the Special Issue Development of Mechanical, Corrosion Resistance, and Antibacterial Properties of Steels)

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