Metal structures corrosion is a problem of global economic importance. Typically, the corrosion process runs slowly, which requires accelerated methods for corrosion behaviour examination. The conditions when accelerated methods are used differ from the real ones, which affects the results obtained. One of the methods that relatively successfully reproduces corrosion in a natural atmosphere is included in the standard EN ISO 11130:2018 – Alternate immersion test in salt solution. Unlike other widespread methods, uneven corrosion occurs here, including spots and pits, which greatly affect the mechanical behaviour of the material. The commercial devices for such tests are quite expensive. This justifies the development and production of one’s own equipment as the one presented in this paper. The design, construction and production of a low-cost device are hereby described. The first results of the tests performed with this machine are also given. The corrosion rate of rods, 6 mm in diameter, from widely used steel grades – S235JR and S235JRC – was determined. The duration of the test was 42 days. The results were compared with those from another corrosion test method with the same duration – immersion in a solution of 3.5% NaCl.

This paper presents a newly developed system for mechanical testing at static loading. The separate modules of the system are described - tensile testing machine, grips, extensometers for axial end transverse deformations, electronic control system. The results obtained during tensile testing with the new system are given. The yield strength, the tensile strength, the elasticity modules and the Poisson’s ratio of general purpose steal S235JRC are determined.

Corroded B235 reinforcing steel rods, which were exposed to an open air environment for 25 years, with a certain specific mass loss, were studied. Test pieces were prepared from them by lathe machining. The test pieces were subjected to accelerated corrosion through an alternate immersion in NaCl solution. The same specific mass loss as on the initial corroded rods was achieved for 52 days. Further the test pieces were cleaned, observed, photographed and tensile tested. The cleaned surfaces and the stress-strain curves of the test pieces were compared with results, obtained from the initial corroded rods. It was found out about the tested steel rods that alternate immersion in salt solution for 52 days is a good simulation of twenty-five-year atmospheric corrosion.

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It is well known that atmospheric corrosion greatly affects the stress-strain properties of reinforcing steel. To be able to assess and forecast the remaining service life of constructions which have been subjected to atmospheric corrosion, it is necessary to have good knowledge of this effect. Research is often complicated to do due to the lack of accurate information on the initial dimensions of the steel parts and the properties of the material of which those parts are made. In this paper an attempt is made to overcome this obstacle. Reinforcing steel rods are tested. Those rods have been subjected to natural atmospheric conditions in a temperate climate zone for 25 years, in vertical orientation. To determine the initial stress-percentage extension curve of those rods test pieces have been made by machining on a lathe – to remove the corrosion layer and to set a standard diameter. The chemical composition and the density of the material are determined by appropriate experiments. The yield strength, the ultimate strength, the percentage elongation after fracture are determined by standard tensile testing. To determine the final stress-percentage extension curve, tensile tests are carried out with the corroded rods without any treatment. A comparison of both curves and analysis of the atmospheric corrosion effect on the stress-strain behavior is made.