opk Current issue
Chloride diffusion and migration coefficients in concretes with CEM I 42.5 R; CEMII/B-V 32.5 R; CEM I 42.5N/SR3/NA cement determined by standard methods and thermodynamic migration model
Politechnika Śląska, Wydział Budownictwa, Katedra Konstrukcji Budowlanych
This article describes how diffusion coefficients of chlorides were determined in ordinary concretes using three different types of commonly used cement: CEM I 42.5 R, CEM II/B-V 32.5 R and CEM I 42.5 N/SR3/ NA according to applicable standards NT BUILD 443, AASHTO T 259, ASTM C 1556 – 03. Determined values were compared with values obtained from short migration tests on these concretes using the thermodynamic migration model with the inverse equation for chloride migration in concrete. Additionally, migration coefficients of chloride ions were determined according to the standard NT BUILD 492 and applying a method proposed by Andrade. This comparison of obtained values of diffusion and migration coefficients was used to evaluate the suitability of valid standard methods and their reference to the method of determining diffusion coefficient according the thermodynamic model of migration.
Keywords: chloride diffusion coefficient, chloride migration coefficient, thermodynamic migration model, diffusion tests, migration tests
2019, Vol. 62, nr 5, s. 162-169
The corrosion resistance of the supporting structure plating elements in relation to the manufacturing technology used
Instytut Mikromechaniki i Fotoniki, Politechnika Warszawska, ul. Św. A. Boboli 8, 02-525 Warszawa, Poland
The main purpose of the work was to determine how the applied technology of producing elements such as the bearing structure influences the resistance in the operation process in an atmospheric environment. The research work was carried out experimentally, determining the rate and intensity of the formation of corrosion centers in the aspect of the product shaping technology applied. The paper focuses on two technologies most commonly encountered in sheet metal forming and machining. They are the punching process and the laser cutting technology. The sample was made in such a way that it was possible to analyze the corrosion behavior both on sharp edges and in hewed sockets to the face of the sheet after the bending process. The aim of the work was achieved by performing experimental studies taking into account the issues contained in the standards PN-EN ISO 9223: 2012, PN-EN ISO 9224: 2012, PN-EN ISO 9225: 2012, PN-EN ISO 9226: 2012 and PN-EN ISO 9227: 2017 comparing the technology, determining the corrosion durability of the samples in the same environment. Based on the results, it was found that samples made with punching process show higher corrosion resistance than laser cuting samples.
Keywords: corrosion resistance of sheets, punching and corrosion, laser cutting and corrosion, corrosion wear of seams
2019, Vol. 62, nr 5, s. 170-175
CORROSION PROTECTION IN PRACTICE:
Basic conditions to obtain and maintain resistance against corrosion of stainless steels
Ancora, Pasywacja metali i konstrukcja zbiorników kontenerowych, Gdańsk
Stainless steels are corrosion resistant due to their ability to passivation which means formation of a thin film, containing increased concentration of chromium, molybdenum and nickel oxides, having thickness of thousands of a micrometer. Naturally occurring passive film is sensitive to local contaminations and defects during construction processes, like welding, grinding and other mechanical treatments. The film of metal oxides is uncompleted, no uniform and unable to be regenerated at the places of damages, or is covered with contaminations or rust. Formation of a proper oxide film that guarantees corrosion resistance can be obtained after pickling and passivation process. The technology applied depends mainly on the type of construction and properties of the stainless steel. Specializing companies perform passivation at their premises or/and in the field. At both cases the same chemicals are applied and presently used technologies allow to perform pickling and passivation process as one step. After the process the chemicals must be precisely removed from the metal surface and elements or constructions might be blown dried. Passivation effects are confirmed by electrochemical potential measurements and by testing of absence of contaminations at the stainless steel surface. The pickling/passivation process should be conducted always in any serious case of stainless steel contamination during exploitation.
Keywords: stainless steels, pickling, passivation
2019, Vol. 62, nr 5, s. 176-180