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1

Corrosion behavior of austenitic stainless steels in road salt solutions

Zatkalíková Viera, Markovičová Lenka, Valčuhová Daniela

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2022

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nr 71 (143)

72--77

EN

Stainless steels are widely used for various automotive components. Some of them (e.g., parts of the exhaust system) are exposed to the external environment. In winter conditions, they are affected by chloride containing road salt solutions, which can lead to the local corrosion of these stainless steel parts. The presented paper is focused on the pitting corrosion resistance of two austenitic stainless steels (AISI 304 and AISI 316L) in 5 wt% and 10 wt% road salt solutions. The evaluation and comparison are based on the potentiodynamic polarization test method carried out at the temperature of 20 ± 2°C. The pitting potentials were determined from the polarization curves. Local corrosion damage of exposed surfaces caused by potentiodynamic polarization in the used solutions was observed by optical microscope. Experimental results confirmed a worse pitting corrosion resistance case, especially for AISI 304 stainless steel in 10 wt% road salt solution.

2

Corrosion tests of metal pipes in drinking water systems using electrochemical methods

Adetunji Olayide R., Oyelowo Mojisola A., Adekunle Nurudeen O., Adeogun Abideen I., Okediran Iliyas.K

Ochrona przed Korozją

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2022

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nr 2

43--49

EN

Metals constitute some of the major materials for making water delivery pipelines. However, the service life of metallic pipelines is affected by corrosion. Mild Steel (MS), Galvanized Steel (GS) and Copper were selected based on their strength and corrosion resistance. They were subjected to Potentiodynamic Polarization (PP) and Electrochemical Impedance Spectroscopy (EIS) investigations using water as the electrolyte from selected sampling points (A, B, C, D and E) on the University of Lagos, Akoka water distribution network. Corrosion current density (Icorr) and Impedance (Z) were measured in A/mm2 and ohms respectively. The morphology of the corroded samples was examined using Scanning Electron Microscope (SEM). The result obtained from PP investigation showed Icorr in the low range for the three metals considered. Similarly, for EIS, Z values measured were high for MS, GS and Cu. Both methods indicated that Cu was the most corrosion resistant material, closely followed by GS and lastly MS. The SEM images clearly showed that among the three specimens, the morphology of Cu remained unaffected by the environment. On the other hand, MS and GS showed evidences of corrosion with pits. The large amounts of iron established in the studied water distribution system, confirmed corrosion of water pipes.

PL

Metale są jednym z głównych materiałów konstrukcyjnych wodociągów. Jednak trwałość metalowych rurociągów jest ograniczona ze względu na korozję. Ze względu na wytrzymałość i odporność na korozję do budowy rurociągów stosuje się stal miękką (MS), stal ocynkowaną (GS) i miedź. Próbki pobrane w wybranych miejscach (A, B, C, D i E) sieci wodociągowej Akoka poddano na Uniwersytecie w Lagos badaniom metodą polaryzacji potencjodynamicznej (PP) i elektrochemicznej spektroskopii impedancyjnej (EIS) z zastosowaniem wody jako elektrolitu. Gęstość prądu korozyjnego (Icorr) i impedancję (Z) zmierzono odpowiednio w A/mm2 i omach. Morfologię skorodowanych próbek zbadano za pomocą skaningowego mikroskopu elektronowego (SEM). Wynik otrzymany w badaniach PP wykazał Icorr w niskim zakresie dla trzech rozważanych metali. Podobnie w przypadku EIS zmierzone wartości Z były wysokie dla MS, GS i Cu. Obie metody wskazywały, że miedź jest najbardziej odpornym na korozję materiałem, a następnie ocynkowana stal o podobnych właściwościach i na końcu stal miękka. Na mikrofotografiach SEM wyraźnie widać, że spośród trzech próbek metali środowisko nie miało wpływu na morfologię Cu. MS i GS wykazały ślady korozji z wżerami. Duże ilości żelaza stwierdzone w badanym systemie wodociągowym potwierdziły korozję rur.

3

Optimized electroless Ni-Cu-P coatings for corrosion protection of steel rebars from pitting attack of chlorides

Mukhopadhyay Arkadeb, Sahoo Sarmila

Engineering Transactions

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2021

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Vol. 69, iss. 3

315--332

EN

Structures, constructions and bridges in coastal areas are greatly affected by the corrosive attack of chlorides. This reduces their lifetime and leads to losses due to their maintenance. This study aims to improve the lifetime and corrosion-proof behavior of steel rebars in the saline environment (3.5% NaCl) by applying electroless Ni-Cu-P coatings with high corrosion resistance. Ni-Cu-P coating was deposited on Fe-600 steel rebars. The coating was deposited by varying bath condition parameters, such as concentration of nickel sulphate, sodium hypophosphite and copper sulphate. This led to a variation in Ni, P and Cu content, and finally, the optimal bath combination was obtained using the Taguchi-based grey relational analysis. For concentrations of 25, 10 and 0.3 g/l nickel sulphate, sodium hypophosphite and copper sulphate, enhanced corrosion resistance of the coated rebars could be achieved with −350 mV Ecorr and 0.4 µA/cm2 Icorr. At the same time, the bare rebars had Ecorr of − 653 mV and Icorr of 11.7 µA/cm2 . .

4

The Influence of the Microstructural Evolution on the Corrosion Resistance of Cold Drawn Copper Single Crystals in NaCl

Koralnik M., Dobkowska A., Adamczyk-Cieslak B., Mizera J.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 1

55--64

EN

The aim of the present work was to determine the influence of the microstructural evolution of copper single crystals with the initial orientations of <001> and <111> after cold drawing on their corrosion resistance. Transmission electron microscopy, X-ray diffraction, and electron backscattering diffraction were used to characterize the microstructural changes. To evaluate the corrosion resistance after deformation, open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization analyses were conducted. The microstructural observations showed the presence of dislocation cell structures and shear bands indeformed sample with initial orientation <001> single crystal, as well as a strongly-developed substructure in sample <111>. The material with initial orientation of <001> was more resistive in analyzed medium than material with the initial orientation of <111>.

5

Microstructure and Electrochemical Behaviors of Equiatomic TiMoVCrZr and Ti-rich TiMoVCrZr High-Entropy Alloys for Metallic Biomaterials

Song Hocheol, Lee Seongi, Lee Kwangmin

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 4

1317--1322

EN

The present study investigated various thermodynamic parameters, microstructures and electrochemical behaviors of TiMoVCrZr and Ti-rich TiMoVCrZr high-entropy alloys (HEAs) prepared by vacuum arc remelting. The microstructures of the alloys were analyzed using X-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FE-SEM), and potentiodynamic polarization tests. The determined thermodynamic values of the Ω-parameter and the atomic size difference (δ) for the HEAs were determined to be in the range of Ω ≥ 1.1, and δ ≤ 6.6% with valance electron configuration (VEC) ≤ 5.0, suggesting the HEAs were effective at forming solid solutions. XRD patterns of the equiatomic Ti20 Mo20 V20 Cr20 Zr20 HEA revealed four phases consisting of the body centered cubic1 (BCC1 ), BCC2 , hexagonal close-packed (HCP), and intermetallic compound Cr2 Zr phases. Three phases were observed in the XRD patterns of Ti-rich Ti40 Mo15 V15 Cr15 Zr15 (BCC, HCP, and Cr2 Zr) and a single BCC phase was observed in Ti-rich Ti60 Mo10 V10 Cr10 Zr10 HEAs. The backscattered-electron (BSE) images on the equiatomic Ti20 Mo20 V20 Cr20 Zr20 HEA revealed BCC and HCP phases with Cr2 Zr precipitates, suggesting precipitation from the HCP solid solution during the cooling. The micro-segregation of Ti-rich Ti60 Mo10 V10 Cr10 Zr10 HEAs appeared to decrease remarkably. The alloying elements in the HEAs were locally present and no phase changes occurred even after additional HIP treatment. The lowest current density obtained in the polarization potential test of Ti-rich Ti40 Mo15 V15 Cr15 Zr15 HEA was 7.12×10-4 mA/cm2 was obtained. The studied TiMoVCrZr HEAs showed improved corrosion characteristics as compared to currently available joint replacement material such as ASTM F75 alloy.

6

Mechanical Properties and Corrosion Behaviors of Aged Ti-4Mo-4Cr-X (X = Sn, V, Zr) Alloys for Metallic Biomaterials

Lee Kwangmin, Lee Gunhee

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 4

1297--1301

EN

The purpose of this study was to investigate the mechanical properties of beta type aged Ti-4Mo-4Cr-X (X = V, Sn, Zr) quaternary alloy for use as a cardiovascular stent. Titanium (Ti) alloys were fabricated using a vacuum arc remelting furnace process. To homogenize the specimens of each composition and remove the micro segregation, all cast specimens were subjected to homogenization at 850°C for 4 h, which was 100°C higher than the β-transus temperature of 750°C. The tensile strength and elongation of the aged Ti-4Mo-4Cr-X (X = V, Sn, Zr) alloys were increased as compared to the homogenized alloys. In addition, many α/β interface boundaries formed after aging treatment at 450°C, which acted as inhibitors of strain and caused an increase in tensile strength. The elongation of Ti-4Mo-4Cr-X alloys consisting of α + β phases after aging treatment was improved by greater than 30%. Results of a potentiodynamic polarization test showed that the lowest current density of Ti-4Mo-4Cr-4Sn with1.05 × 10-8 A/cm2 was obtained. The present Ti-4Mo-4Cr-X alloys showed better corrosion characteristics as compared to the 316L stainless steel and L605 (Co-Cr alloy) cardiovascular stent alloys.

7

Corrosion Inhibition of API 5L X52 Carbon Steel by 1-Ethyl-3-methylimidazolium-methanesulphonate and 1-Ethyl-3-methylimidazolium Acetate Ionic Liquids in Hydrochloric Acid

Ikpi Magdalene Edet, Obono Okama Ebri

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 1

295--304

EN

The corrosion inhibition behaviour of 1-Ethyl-3-methylimidazolium-methanesulphonate (EMIM[MS]) and 1-Ethyl-3-methylimidazolium acetate (EMIM[Ac]) on API 5LX-52 carbon steel in 2 M HCl was investigated using weight loss, potentiodynamic polarization and electrochemical impedance methods. The corrosion rates of carbon steel decreased in the presence of these ionic liquids. The inhibition efficiencies of the compounds increased with concentration and showed a marginal decrease with a 10°C increase in temperature. Polarization studies showed the compounds to be mixed type inhibitors with stronger anodic character. The adsorption mechanism of both compounds on the metal surface was via physical adsorption and the process obeyed the El-Awardy kinetic-thermodynamic model. The associated activation energy of corrosion and other thermodynamic parameters were calculated to elaborate on the thermodynamics and mechanism of the corrosion inhibition process. EMIM[MS] was found to inhibit the corrosion of carbon steel better than EMIM[Ac] and is attributed to the presence of the highly electronegative sulphur atom in its structure and its larger molecular size.

8

Effect of Cold Rolling on Electrochemical Impedance Behavior of New β-Type Ti-6Mo-6V-5Cr-3Sn-2.5Zr Alloy

Song Hocheol, Zakiyuddin Ahmad, Kim Sinhye, Lee Kwangmin

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 2

487--490

EN

In this study, the corrosion properties of Ti-6Mo-6V-5Cr-3Sn-2.5Zr alloy were investigated as a function of the cold rolling ratio and annealing temperature. The annealing treatment was carried out at temperature of 680°C, 730°C, and 780°C. The highest corrosion potential observed in the specimen with a 10% rolling ratio was 179 mV, which was more positive than that of the nonrolled specimen (–0.214 VSSC). The lowest corrosion current density (1.30×10-8 A/cm2) was observed in the non-rolled specimen which suggested that the integrity of its passive oxide layer was superior to that of the cold-rolled specimens. Time-dependent EIS evaluation revealed that the consistency of the passive oxide layer was highly affected by the subjected rolling ratio over time.

9

Inhibitive efficiencies of some selected liquid hydrocarbons as anti-corrosives for stainless and mild steel samples in HCl

Adetunji O. R., Nwankwo O. K., Adesusi O. M., Adetunji O. W., Makinde V. O.

Ochrona przed Korozją

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2017

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nr 10

339--343

PL

Korozja to proces rozkładu metalu prowadzący do pogorszenia jego własności użytkowych w wyniku działania czynników środowiskowych. W przemyśle naftowym, metale te są poddane działaniu różnych czynników środowiskowych, które skracają ich żywotność. W badaniach wykorzystano Polaryzację Potencjodynamiczną (PP) do oceny skuteczności benzyny, nafty oraz oleju napędowego jako inhibitorów korozji Stali Miękkiej (SM) oraz Stali Nierdzewnej (SN) umieszczonej w środowisku HCl. PP przeprowadzono z wykorzystaniem 8 próbek metalowych pełniących funkcje elektrod roboczych umieszczonych w medium w postaci 1 M HCl o pH 1,2 w roztworze osobno z 0,1% benzyny (DHCL), oleju napędowego (DHCl) oraz nafty pełniących funkcję inhibitorów. Na podstawie badań PP określono gęstości prądów korozyjnych, które wykorzystano do ustalenia Szybkości Korozji (SK). Odnotowano pH medium. Za pomocą Skaningowego Mikroskopu Elektronowego wykonano zdjęcia skorodowanych próbek. Szybkość korozji SN na podstawie PP wynosiła 0,0549, 0,0199, 0,0066 oraz 0,0093 mm/rok odpowiednio dla HCL, PHCL, DHCL oraz KHCL, a dla SM wynosiła odpowiednio 0,515, 0,009, 0,057 oraz 0,006 mm/rok. Skuteczność inhibicji zatem była większa dla SN niż dla SM odpowiednio w przypadku DHCL, PHCL oraz KHCL. Uzyskane za pomocą SEM zdjęcia SN oraz SM wskazywały na obecność produktów korozji w medium. Podsumowując, inhibicja korozji była skuteczna w przypadku SN w DHCL, podczas gdy wyższą szybkość korozji odnotowano dla SM w HCl.

10

Corrosion performance of aluminum zinc coated steel in tomato, orange and pineapple juices

Adetunji O. R., Akinyemi O. J., Kuye S. I., Dare E. O.

Ochrona przed Korozją

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2016

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nr 3

66--69

EN

Fruit juice processing facilities, storage and waste fruits disposable cans are sourced based on several considerations ranging from cost, durability and health implications. This study evaluated the corrosion performance of Aluminum zinc coated steel (Aluzinc), in three media (tomato, orange and pineapple juices). These media were chosen due to their social and economic importance. Samples of Aluzinc, were prepared by cutting into 3 × 3 cm from 0.5 mm thick plate. Three of the prepared samples were used for Potentiodynamic Polarization Experiments (PPE) while 54 samples were used for Weight Loss Method (WLM). Each of the prepared samples for WLM was cleaned, weighed and immersed in the media for 30 days. The samples were removed at the end of immersion, cleaned and reweighed. The weight losses obtained for WLM were used to evaluate the corrosion rates. The results obtained for the corrosion rates in mm/yr using PPE in orange, pineapple and tomato juices were 0.0065, 0.0303, and 0.0062 for Aluzinc. The measured pH values for the media ranged from 4.1 to 8.3. The corrosion rate of aluzinc was highest in Pineapple juice than in Tomato and Orange juice after 30 days immersion in the media. SEM images of corroded metallic samples indicated the effect of corrosion on them.

PL

Urządzenia używane w przetwórstwie soków, jak i pojemniki jednorazowe stosowane do magazynowania soków i ich odpadów, dobierane są z uwzględnieniem ich ceny, trwałości oraz bezpieczeństwa dla zdrowia. Przeprowadzono badania zachowania stali z powłoką cynkowo-aluminiową umieszczonej w trzech różnych mediach (sok pomidorowy, pomarańczowy i ananasowy). Media te wybrano ze względu na ich znaczenie społeczne i gospodarcze. Próbki alucynku przygotowano wycinając płytki o rozmiarach 3 × 3 cm z blachy o grubości 0,5 mm. Trzy z przygotowanych próbek użyto w badaniach metodą polaryzacji potencjodynamicznej, a 54 próbki wykorzystano do oznaczania ubytku masy. Każdą z próbek przeznaczonych do badań metodą WLM wyczyszczono, zważono i zanurzono w wybranym medium przez 30 dni. Następnie próbki wyciągnięto, wyczyszczono i ponownie zważono. Uzyskane wartości ubytku masy wykorzystano do oceny stopnia korozji. Szybkość korozji wyrażona w mm/rok określona na podstawie badania PPE po zanurzeniu próbek w soku pomarańczowym, ananasowym i pomidorowym wynosiła odpowiednio 0,0065, 0,0303 i 0,0062. Wartości pH dla użytych mediów mieściły się w przedziale od 4,1 do 8,3. Szybkość korozji alucynku była największa w przypadku soku ananasowego, następnie pomidorowego, a na końcu pomarańczowego. Próbki metalowe widziane na zdjęciach SEM nosiły ślady korozji.

11

The effect of heat treatment simulating porcelain firing processes on titanium corrosion resistance

Sokołowski G., Rylska D., Sokołowski J.

Acta of Bioengineering and Biomechanics

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2016

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Vol. 18, no. 2

93--102

EN

Purpose: Corrosion resistance of titanium used in metal-ceramic restorations in manufacturing is based on the presence of oxide layer on the metal surface. The procedures used during combining metallic material with porcelain may affect the changes in oxide layers structure, and thus anticorrosive properties of metallic material. The aim of the study was an evaluation of potential changes in the structure and selected corrosion properties of titanium after sandblasting and thermal treatment applicable to the processes of ceramics fusion. Methods: Milled titanium elements were subjected to a few variants of the processes typical of ceramics fusion and studied in terms of resistance to electrochemical corrosion. The study included the OCP changes over time, measurements of Icorr, Ecorr and Rp as well as potentiodynamic examinations. Surface microstructure and chemical composition were analyzed using SEM and EDS methods. Results: The results obtained allow us to conclude that the processes corresponding to ceramic oxidation and fusion on titanium in the variants used in the study do not cause deterioration of its anticorrosive properties, and partially enhance the resistance. This depends on the quality of oxide layers structure. Conclusions: Titanium elements treated by porcelain firing processes do not lose their corrosion resistance.

12

The influence of molibdenum on corrosion resistance of sintered austenitic stainless steels

Szewczyk-Nykiel A.

Czasopismo Techniczne. Mechanika

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2015

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Y. 112, iss. 4-M

131--142

EN

Molybdenum was introduced into sintered austenitic stainless steels to improve their corrosion resistance. The influence of different Mo contents on the pitting corrosion resistance of AISI 304L and 316L steels in 0.1 M sodium chloride solution has been investigated. The corrosion behaviour was evaluated by potentiodynamic polarisation method. Sintered Mo-containing 304L steel is less prone to pitting corrosion in environment containing chlorides than 316L with Mo addition. The introduction of molybdenum to 304L steel resulted in an improvement of corrosion resistance. This steel exhibits the highest value of polarisation resistance as well as the lowest value of corrosion rate.

PL

Molibden wprowadzono do austenitycznych stali nierdzewnych w celu poprawy ich odporności na korozję. Badano wpływ różnej zawartości molibdenu na odporność na korozję wżerową stali AISI 304L i 316L w 0.1 M roztworze chlorku sodu. Zachowanie korozyjne oceniano metodą polaryzacji potencjodynamicznej. Spiekana stal 304L zawierająca molibden jest mniej podatna na korozję wżerową w środowisku zawierającym chlorki niż 316L z dodatkiem Mo. Wprowadzenie molibdenu do stali 304L spowodowało poprawę odporności na korozję. Stal ta wykazuje najwyższą wartość oporu polaryzacji, jak i najniższą wartość szybkości korozji.

13

The effect of silicon content on the pitting corrosion of duplex stainless steel weldment

Lee B.H., Lee H.J., Kang D.W., Lee H.W.

Archives of Materials Science and Engineering

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2014

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Vol. 67, nr 2

60--69

EN

In this study, the effect of Si content at a welded DSS on the pitting resistance was investigated. Design/methodology/approach: The δ-ferrite fraction increased due to addition of Si, and the amount of γ2 decreased. In the ferric chloride pitting test, the weight reduction range decreased due to an increase in the Si content. As to the location, pittings occurred intensively at the grain boundary or within the austenite grain due to the difference in PREN caused by the differential solid solubility in each phase. Findings: As a result of the potentiodynamic polarization test, while the Epit(Critical Pitting Potential) of all specimens depending on the temperature were observed to be similar at froom temperature up to 45°C, the reduction range of the Epit was found to be small at the temperature higher than 45°C as Si content increased. This was found to be because of formation of SiO2 in the passive film. Research limitations/implications: Higher the addition of Si, the more the number of pittings generated at the grain boundary decreased as the coherence of the passive film increased by the Si accumulated at the boundary. Originality/value: In this study, we intend to investigate the effect of Si element addition on the pitting resistance of the duplex stainless steel welding zone.

14

Inhibitive tendency of zinc gluconate for aluminium alloy in sulphuric acid solution

Sanni O., Loto C. A., Popoola A. P. I.

Polish Journal of Chemical Technology

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2013

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Vol. 15, nr 4

60-64

EN

The corrosion inhibition of aluminium alloy in 0.5M H2SO4 solution in the presence of zinc gluconate at 301 K was investigated using weight loss and an electrochemical method. Surface analysis of the aluminium alloy sample was reviewed by a high resolution scanning electron microscope equipped with energy dispersive spectroscopy (HRSEM/ EDS). The readings were taken after 48 h for 28 days while the concentration of the inhibitor was varied from 0.5 to 2.0% g/v with an interval of 0.5. The result of the investigation shows that zinc gluconate has a good corrosion inhibition effect for aluminium alloy in 0.5 molar sulphuric acid solution and its efficiency attains more than 67% at 1.5% g/v concentration of zinc gluconate at 301 K. The potentiodynamic polarization data showed that zinc gluconate acts as a mixed type corrosion inhibitor. The adsorption of zinc gluconate on aluminium alloy has been found to obey Freundlich adsorption isotherm at all the concentration of zinc gluconate studied. The results obtained from different methods are in good agreement.

15

Cynkowanie termodyfuzyjne - trwałe i ekologiczne zabezpieczenie antykorozyjne małych i średnich elementów

Mechowicki K.

Inżynieria Powierzchni

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2012

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nr 4

32-37

PL

Artykuł poświęcony jest badaniom struktur i właściwości powłok cynkowych wytwarzanych technologią termodyfuzyjną w porównaniu do powłok wytwarzanych elektrochemicznie oraz zanurzeniowo. Badania struktur powłok przeprowadzono za pomocą skaningowego mikroskopu elektronowego oraz mikroskopu metalograficznego. Właściwości mechaniczne powłok charakteryzowano na podstawie pomiaru mikrotwardości metodą Knoopa, zaś odporność korozyjną badano elektrochemiczną metodą potencjo dynamiczną oraz w komorach solnych. Analiza ta pozwala na dobranie najbardziej korzystnej metody zabezpieczenia antykorozyjnego wyrobów ze stali w odniesieniu do oczekiwań stawianych w warunkach eksploatacji.

EN

Structures and properties of thermodiffusion zinc layers with comparison to the electrochemical layers and hot zinc layers have been studied. Investigation of structures was done with the use of scanning electron microscope and metallographic microscope. Mechanical properties of coatings were investigated by Knoop microhardness equipment. Studies of corrosion resistance were made using potentiodynamic polarization method and in salt spray chamber. Conducted research and analysis allowed to determine the best method of zinc coating, depending on the properties required.

16

Zachowanie korozyjne kompozytu A359-cząsteczki SiC

Bieniaś J., Surowska B.

Kompozyty

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2003

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R. 3, nr 8

380-384

PL

Artykuł przedstawia wyniki badań podatności na korozję materiału kompozytowego o osnowie aluminium stopu aluminium 359 (Aluminium Association), zawierającego 20% obj. cząsteczek SiC (359/20%SiC). Kompozyt 359/20%SiC został wytworzony w Instytucie Odlewnictwa w Krakowie. Znajduje on zastosowanie jako nowoczesny materiał konstrukcyjny w przemyśle samochodowym, szczególnie na tłoki i tarcze hamulcowe. Wprowadzenie cząstek wzmacniających znacząco może zmieniać zachowanie korozyjne tych materiałów. Publikowana literatura w zakresie kompozytów o osnowie stopów aluminium jest ograniczona i często sprzeczna. Jest to spowodowane faktem rozmaitości osnowy kompozytów i faz zbrojących, które mogą powodować zupełnie inne zachowanie korozyjne. Ponadto różne parametry wytwarzania wpływają na mikrostrukturę materiałów kompozytowych, a w konsekwencji na ich zachowanie korozyjne. Badania odporności na korozję kompozytu 359/20%SiC wykonano za pomocą przyśpieszonych badań elektrochemicznych metodą potencjodynamiczną. Analizę korozyjną tego materiału odniesiono do charakterystyki korozyjnej stopu aluminium AK9 (AlSi9Mg). Pomiary potencjodynamiczne wykonano w 3,5% wag. roztworze NaCl (pH = 7,0) w temperaturze 25°C. Badania mikrostrukturalne przeprowadzono za pomocą mikroskopu optycznego ZEISS i skaningowego mikroskopu elektronowego (SEM) Hitachi S-3500N. W strukturze kompozytu na tle roztworu stałego i drobnoziarnistej eutektyki widoczne są cząsteczki węglika krzemu. Rozkład cząsteczek SiC w strukturze był dość równomierny (rys. la). Przebieg krzywych polaryzacji anodowej w 3,5% NaCl wskazuje, że są to krzywe metalu ulegającego samorzutnej pasywacji (rys. 2). Wyznaczone potencjały Ek, Eb, Er,[ delta]Eb, [delta]Er, z badań elektrochemicznych i analizy krzywych polaryzacji anodowej dla kompozytu i stopu AK9 są bardzo podobne (tab. 2). W strukturze stopu AK9 (rys. 3) występują liczne wżery, których głębokość zawiera się w granicach 8--16 }mikro]m. Wżery lokują się w eutektyce [alfa]+Si. W przypadku materiału kompozytowego 359/20%SiC obserwuje się jeszcze bardziej liczne i głębsze wżery (10--24 [mikro]m), które także lokują się w eutektyce [alfa]+Si pomiędzy cząsteczkami SiC (rys. rys. 4 i 5). Przeprowadzone badania nie wykazały znaczącego wpływu cząsteczek SiC na wzrost podatności na korozję wżerową w porównaniu do stopu AK9, co potwierdzają również dane literaturowe.

EN

The paper presents results of the studies on the susceptibility of Aluminium Matrix Composite to corrosion. The subject of the examinations was a composite with the 359 aluminium alloy matrix (Aluminium Association) containing 20 vol.% of SiC particles (359/20%SiC). The 359/20%SiC composite has been synthesized at the Foundry Research Institute in Cracow. This material can be applied as a modern construction material in automotive industry, particularly for brake discs and pistons. However, the addition of the reinforcement particles could significantly influence the corrosion behaviour of these materials. Generally published literature on the corrosion of aluminium-based composites is rather limited and often contradictory. This is due to the fact that there is a variety of aluminium alloy matrix and reinforcement type combinations which may exhibit a completely different corrosion behaviour. In addition, processing parameters can heavily affect composite microstructure and, consequently, their corrosion behaviour. The studies on the 359/20%SiC composite corrosion resistance were carried out by accelerated electrochemical studies using the potentiodynamic method. The corrosion analysis of this material was then related to the corrosion characteristics of AK9 (AlSi9Mg) aluminium alloy. The potentiodynamic measurements were taken in the 3.5 wt.% NaCl water solution (pH = = 7.0) at the temperature of 25°C. Microstructure analysis of the specimens was examined using ZEISS model optical microscope and Hitachi S-3500N scanning electron microscopy (SEM). Silicon carbide particles were seen in the matrix on base of the [alpha]-Al solid solution, a fine-grained eutectic [alpha]+Si (Fig. 1a). Distribution of SiC in the structure was quite uniform. The course of the anodic polarization curves in the 3.5 wt.% NaCl solutions suggests characteristic curves for the metal that undergoes spontaneous passivation (Fig. 2) Potentials of the Ek, Eb, Er, [delta]Eb, [delta]Er determined in electrochemical studies and analyses of the anodic polarisation curves, for both, composite and AK9 alloy, are very similar (Tab. 1). In the microstructure of AK9 alloy (Fig. 3) there arę numerous pits whose depth ranges from 8--16 [micro]m. The pits are located in [alpha]+Si eutectic. In the case of the composite material more numerous and deeper pits (10--24 [micro]m) were observed which also locate in the [alpha]+Si eutectic between SiC particles (Figs. 4, 5). The conducted examinations did not show significant influence of SiC particles on the increase of susceptibility to pitting corrosion in comparison to AK9 alloy, what is confirmed by the literature data.

17

Structure and potentiodynamic polarization study of aluminium matrix-graphite particles composite.

Bieniaś J., Surowska B., Sobczak J.

Inżynieria Materiałowa

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2001

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R. XXII, nr 4

224-226

EN

The paper presents the microstructural characteristics of A356/5.7wt.%GRp (graphite particles) composite and susceptibility to pitting corrosion in a typical corrosive environment. Structural studies confirm the uniform distribution of the reinforcing phase in the whole composite bulk and confirm good compatibility between reinforcing phase and matrix. The studies on A356/5.7GRp composite resistance to corrosion were investigated through potentiodynamic techniques in 3.0 wt% NaCl aqueous solution at the temperature of 25 degrees centigrade and 60 degrees centigrade. The course of polarization curves, pitting potential (Epit), corrosion potential (Ecorr), repassivation potential (Erp), microstructural image and numerous, deep pits (10-130 micrometers) suggest susceptibility of the A356/5.7GRp composite to pitting corrosion.

PL

W pracy przedstawiono charakterystykę mikrostrukturalną kompozytu A356/5.7GRp (cząsteczki grafitu) i podatność na korozję wżerową w typowym środowisku korozyjnym. Badania strukturalne potwierdziły równomierny rozkład fazy zbrojącej w całej objętości kompozytu i dobre połączenie fazy zbrojącej i osnowy. Badania odporności na korozję kompozytu A356/5.7GRp prowadzono metodą potencjodynamiczną w 3% wag. roztworze wodnym NaCl w temperaturze 25 i 60 stopni Celsjusza. Kształt krzywych polaryzacji, potencjał przebicia (Epit), potencjał korozji (Ecorr), potencjał repasywacji (Erp), obraz mikrostrukturalny i liczne głębokie wżery (10-130 mikrometrów) sugerują podatność A356/5.7GRp na korozję wżerową.