Concrete structures: on-site electrochemical techniques and concrete resistivity to predict service life
Part 1: Corrosion measurement techniques
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.
2019, Vol. 62, nr 1, pp. 2-10
Influence of brine on protective properties of refinish coatings
Instytut Eksploatacji Pojazdów i Maszyn, Wydział Mechaniczny, Uniwersytet Technologiczno-Humanistyczny, Radom
The paper presents results of investigations concerning brine influence on properties of polymer refinish coatings used in paint shops for production of protective-decorative coats on car bodies. Two kinds of three-layer coating systems were investigated in which a base coating was made of solvent-based acrylic paint while a top coat was made of solvent-based acrylic lacquer. The coating systems differed in interlayer composition which was made of polyester or polyurethane paint. Made investigations proved that action of the brine in the form of NaCl 5% water solution reduced durability of adhesive connection between base coating and steel substrate surface. Also a type of interlayer applied in coating system has an essential influence on its adhesive strength as in entire investigation period (0÷2016 h) the coating system with polyester interlayer revealed higher adhesive strength than the one with polyurethane interlayer. Moreover, coating systems with polyester interlayer, subjected to brine ageing, show higher stability of roughness parameters Ra and Rz in comparison with the coating systems with polyurethane interlayer. The coating systems with polyester interlayer manifest also higher durability of gloss than the ones with polyurethane interlayer.
Keywords: refinish coating, brine ageing, destruction, adhesion
2019, Vol. 62, nr 1, pp. 11-18
CORROSION PROTECTION IN PRACTICE
Omission is a deadly sin
European Federation of Corrosion
Objects conceived for critical, heavy, public utilisation like bridges, viaducts, dams, harbours, anti-seismic buildings have to be designed and, of course, realised following criteria of reliability and durability. The first of these two “must” is obtained through skilful design and careful choice of both materials and assembling techniques. The second one is left in the hands of the knowledge of the reactions of the assembled structure and its components towards the environment during the whole service life.
Keywords: design, reliability, durability, prevention, maintenance, inspection
2019, Vol. 62, nr 1, s. 19-21