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Influence of temperature on corrosion resistance of austenitic stainless steel in cl¯ containing solutions

Zatkalíková Viera, Markovičová Lenka

Production Engineering Archives

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2019

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Vol. 25

43--46

EN

Temperature is considered a complicated external factor of the susceptibility of stainless steels to the pitting. This paper deals with the corrosion behaviour of AISI 316Ti stainless steel in temperature range 22 - 80°C in aggressive chloride environments (3 and 5% FeCl3 solutions). The corrosion resistance of tested steel is evaluated on the base of results of exposure immersion tests and cyclic potentiodynamic tests. According to the obtained results the resistance of AISI 316Ti to the pitting is markedly affected by temperature changes in the range 22 - 80°C. Intensity of corrosion attack increases with the rise of Cl¯ concentration. Gentle changes of temperature and Cl¯ concentration cause significant differences in character of local damage. The appearance of pitted surfaces changes with the rise of the temperature (a density of pitting increases, a size of pits decreases). The strongest change in appearance is observed between 40 and 50ºC.

2

The Influence of Plastic Forming Processes on the Dissolution Rate of Biocompatible Mg Alloys

Boczkal S., Karaś M., Korczak P., Kapinos D., Koprowski P., Szymański W., Wroński S.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 3

997--1004

EN

The effect of plastic deformation process on the dissolution rate of biocompatible Mg alloys was investigated. Two biocompatible MgLi1Ca0,2Zn1 and MgLi1Ca1Zn1 alloys were selected for the study. The alloys were deformed on a 100T press at a temperature of 350°C by conventional extrusion and by the equal channel angular extrusion process (ECAE). The grain size analysis showed a high degree of the grain refinement from approximately 110 mm in the initial state to 2.8 mm after the 3rd pass of the ECAE process. Compared to as-cast state, the degree of strengthening has increased after plastic forming. The results of biodegradation tests have shown a significant increase in corrosion rate after both conventional extrusion and ECAE, although after subsequent ECAE passes, this rate was observed to slightly decrease in the MgLi1Ca1Zn1 alloy. Based on the results of macro- and microstructure examinations, the corrosion progress in samples after the extrusion process was described.

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Electrochemical Corrosion of Magnesium Alloy AZ31 with Additive Lithium

Przondziono J., Hadasik E., Szala J.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 4

2359--2363

EN

The purpose of performed tests was evaluation of resistance to electrochemical corrosion of extruded magnesium alloy AZ31 with additive of 4.5% Li. Corrosion tests were performed in 0.01-2.0 M NaCl solutions. Potentiodynamic tests enabled to register polarisation curves. With application of stereoscopic microscope Nikon SMZ745T and electron scanning microscope Hitachi S-4200, the surface of the alloy was observed after immersion tests performed in 1-6 days. Results of performed tests prove explicitly deterioration of corrosion properties of the alloy with the increase of molar concentration of NaCl solution. It can be seen that corrosion process is intensive and that intensity increases with the increase of solution concentration and extension of exposure time.

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Ocena własności korozyjnych stopu magnezu AZ 91 w środowiskach o różnej agresywności chemicznej

Gędłek K., Sułkowski B., Nowak M., Kozik A.

Rudy i Metale Nieżelazne Recykling

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2016

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R. 61, nr 4

155--158

PL

W pracy badano odporność korozyjną stopu AZ91 w środowiskach o różnej agresywności chemicznej. Zastosowano trzy metody badawcze oceny stopnia korozji: metoda potencjodynamiczna, badanie w komorze solnej oraz badanie zanurzeniowo grawimetryczne. Badania prowadzone były w środowisku wody zdemineralizowanej, jako środowisku o niskiej aktywności chemicznej, w środowisku roztworu Na2SO4, jako środowisku o średniej aktywności chemicznej oraz w środowisku roztworu NaCl, jako środowisku o wysokiej agresywności chemicznej. Badania wykazały, że stop AZ91 charakteryzuje się różną skłonnością do korozji w zależności od badanego środowiska. Podatność korozyjna, oceniana na podstawie gęstości prądu korozji w przypadku badań metodą potencjodynamiczną wzrosła o ok. 275%, gdy rolę środowiska korozyjnego pełnił roztwór NaCl, w porównaniu do wody zdemineralizowanej. Na podstawie wyników badań w komorze solnej, określono szybkość ubytku masy w wyniku korozji dla badanego stopu AZ91. Stwierdzono, że po upływie 24 godz. ubytek masy próbki zanurzonej w środowisku NaCl wynosił 1,4% dając tym samy dużą szybkość korozji. Przyczyną niskiej odporności korozyjnej stopu AZ91, biorąc pod uwagę wpływ agresywności środowiska korozyjnego oraz prędkość ubytku masy badanego stopu AZ91, jest duża procentowa zawartość (w porównaniu do innych stopów magnezu) fazy międzymetalicznej Mg17Al12, która może tworzyć mikro-ogniwo galwaniczne z materiałem osnowy obniżając odporność korozyjną stopu AZ91.

EN

In this study the corrosion resistance at the AZ91 alloy in environments with different chemical activity where studied. Three research methods were used to assess the corrosion rote. potentiodynamic method, salt spray test and immersion tests. 5tvdies were conducted in environment of deminemliled water as environment of low chemical activity, in Na2SO4 solution, a medium of on overage chemical activity and in NaCl solution as on environment of high chemical activity. Different susceptibility to corrosion depend on the test environment Potentiodynamic studies have shown thot the AZ91 alloy has a much lawer corrasion resistance in NaCl solution (275% lower) compared to the demineraliled water Based on the results in the salt spray chamber determined the weight loss off he samples. lt was found that often 24h of exposure in the salt spray environments the weight loss of analyzed magnesium alloy AZ91 was J.4%. Based on the obtained research the results of poar corrasion resistance of the AZ9 J magnesium alloy is high aggressiveness of corrosion environment and a large percentage of (compared to other magnesium allays) intermetallic MgJ 7AI1?, which con caused galvanic corrosion. Corrosion studies where confirmed by metoliographic observation using scanning electron microscope (5EM) The result where compared with literature data.

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Corrosion resistance of high-manganese austenitic steels

Grajcar A., Kołodziej S., Krukiewicz W.

Archives of Materials Science and Engineering

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2010

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Vol. 41, nr 2

77-84

EN

Purpose: The aim of the paper is to compare the corrosion resistance of two new-developed high-manganese austenitic steels in 1N H2SO4 and 3.5% NaCl solutions. Design/methodology/approach: The steels used for the investigation were thermo-mechanically rolled and then solution heat-treated from a temperature of 850°C. Corrosion resistance of investigated steels was examined using the immersion test. The specimens were weighed and dipped in the prepared solutions for 100 h. After the test, the percentage weight loss was calculated. The metallographic investigations of corrosion damages included light and scanning electron microscope observations both in the polished and etched states. Findings: It was found that after the thermo-mechanical processing one steel is characterized by an austenitic structure with numerous annealing twins, whereas in the second steel ε and α' martensite plates in an austenitic matrix were observed. According to the results of the immersion tests it was found that the examined steels exhibit a comparable corrosion resistance. They show very poor corrosion resistance in H2SO4 solution and low corrosion resistance in NaCl medium. The weight loss in chloride solution is much lower, what is explained by different corrosion mechanisms. In both the solutions, the intensive general corrosion and corrosion pitting were observed. In acidic medium they are created in a way of hydrogen depolarization and in NaCl in the way of oxygen depolarization. Research limitations/implications: To investigate in more detail the corrosion behaviour of high-manganese austenitic steels, the investigations should include polarization tests and an analysis of corrosion products. Practical implications: The obtained results can be used to search for the appropriate way of improving the corrosion resistance of high-manganese steels with a single-phase austenitic structure as well as the austenite structure containing ε and α' martensite. Originality/value: The corrosion resistance of two types of advanced high-strength high-manganese austenitic steels with different initial structures was compared in acidic and chloride solutions.