opk Current issue
Concrete structures: on-site electrochemical techniques and concrete resistivity to predict service life
Part 2: Service life of structural concrete, present and future challenges
CIMNE: International Center for Numerical Methods in Engineering, Spain
Concrete protects the steel of the reinforcements in a similar manner than do the paints but with the particularity that it is a material chemically active and evolving for decades. Concrete provides a very alkaline electrolyte encapsulated in its pore network. The steel may remain passive indefinitely but chlorides and atmospheric carbon dioxide penetrate the pores and reaching the reinforcement promote corrosion, which impairs the concrete structural properties inducing the cover cracking and the loss in steel-concrete bond. Calculation of service life is becoming an important subject in engineering terms due to the increasing demand to produce buildings and infrastructures with service life beyond 100 years. In the paper focus will be devoted to two main areas: 1) the measurement techniques in concrete and permanent probes, including on site methods for large structures and contactless (inductive) methods 2) the illustration of the corrosion resistance control exerted by concrete resistivity which enables the calculation of the diffusion of ions through the concrete and the prediction of the corrosion rate in function of the climatic conditions.
The first part was published in “Ochrona przed Korozją”, issue 1/2019.
2019, Vol. 62, nr 2, pp.36-40
The influence of bond-coat thickness on the temperature distribution and stress level in thermal barrier coatings system
Silesian University of Technology, Institute of Materials Engineering, 40-019 Katowice, Krasińskiego Street 8, Poland
The paper presents the results of numerical calculation of the temperature distribution and thermal stresses in model of two layered thermal barriers coatings of DCL type deposited on the superalloy coupons with NiCrAlY bond-coat. The variable parameter was the thickness of bond-coat layers. In all cases it was assumed that the bond-coat would be the NiCrAlY type coat obtained by plasma spraying, just as the outer insulating layer. The thickness of the bond-coat layer is 100 μm to 300 μm. As the substrate material, the In 625 nickel superalloy was adopted. The insulation layer of TBC systems was built from outer sublayer based on La2Zr2O7 (LZO) ceramic and internal layer was built from conventional 8YSZ. A total thickness of insulation layer was assumed as 300 μm. Presented analysis showed that the overall thickness of bond-coat has important influence on the temperature distribution as well as the thermal stresses. The maximum temperature differences between extreme thickness value was calculated on the level of 50°C.
Keywords: FEM, bond-coat, thermal barrier coatings, temperature distribution, thermal stress, double-ceramic-layer
2019, Vol. 62, nr 2, pp.41-45
CORROSION PROTECTION IN PRACTICE
Corrosion education: an applied science with constant awareness
Europejska Federacja Korozyjna / European Federation of Corrosion
Polskie Stowarzyszenie Korozyjne
Corrosion cost is the sum of many different contributions some of which are unavoidable end hardly reducible. Surprisingly enough, the enormous efforts of R&D during one century were unable to reduce costs to less than 6% of GNP. The main reasons have to be looked for in the increased complexity of structures, increased cost of materials and especially of coatings, both health and ecological restrictions, but wrong practices account for 30-40% of total. Hence a widespread urgent need of corrosion education and of a logistic of anticorrosion management.
Keywords: corrosion, corrosion cost, corrosion control, corrosion education
2019, Vol. 62, nr 2, pp.46-48
Courses not only for corrosion inspectors
Instytut Badawczy Dróg i Mostów, Warszawa
The corrosion consciousness is not the wake-up from a dreamland. It’s the result of hard education work. It needs hard education work, including, e.g. the corrosion courses. Among them, most popular ones are provided by FROSIO and NACE as called on to form and up-date Inspectors. However, the inspector knowledge does not cover all needs coming from designers, investors and supervisors. Road and Bridge Research Institute together with Polish Corrosion Society in the last 20 years has been organizing courses for both metal and concrete protection: “Designing and supervising of anticorrosive protection on steel constructions” and “Designing and supervising of anticorrosive protection on concrete constructions”. They started as devoted to Road and Bridges Polish Administration only, but because of the awareness of the absence of such a form of education inside other infrastructure branches, the programs were widespread and multi-tailored. This paper will try to show how the long term planned offer of organized, structured, tailored courses influenced both corrosion awareness and consciousness in Poland.
Keywords: courses, protection from corrosion, corrosion Inspector
2019, Vol. 62, nr 2, pp.49-52