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Erosion corrosion, i.e., flow-induced localized corrosion (FILC) is initiated when flow dynamic forces surpass the fracture energy of protective layers or scales on metals. With a new model the maximum interaction energies between flowing media and solid walls can be quantified in terms of ''freak'' energy densities created during singular events (freak events) of perpendicular impacts by near-wall microturbulence elements. The freak energy densities are in the megaPascal range and match well in the order of magnitude with fracture energies of protective layers and can be estimated from Wavelet diagnostics of electrochemical current noise measured at microelectrodes under mass transport controlled conditions. This solves the problem that wall shear stresses, generally used to quantify critical flow intensities for FILC initiation, range several orders of magnitude (Pa range) below the fracture energies of protective layers. The new advanced model allows for the first time to quantify the maximum fluid dynamic forces exerted on solid walls under different turbulent and disturbed flow conditions (onephase liquid flow on jet impinged surfaces and on coupons in rotated cages, surfaces impacted by slug flow and gas-pulsed impinging jets). Drag reducing additives were shown to reduce freak energy densities to values significantly below fracture energies of protective layers and hence inhibit initiation of FILC. The onset of FILC can be monitored online with the newly developed CoulCount method, an easy-to-use, non-invasive diagnostic tool which evaluates electrochemical current noise between jet impinged electrode pairs made from the metals to be tested.

The prevention of corrosion in reinforced concrete structures can be achieved by different means. The aim of this paper is to present the efficiency of corrosion prevention using silane hydrophobic impregnation, through laboratory investigations as well from long term field studies. The laboratory investigation was carried out in Zürich, is based on modified ASTM C109, where the product was applied on cracked concrete beams (before cracking and before corrosion initiation; after cracking and before corrosion initiation and finally after cracking and after corrosion initiation). The long term field studies were carried out over 12-years exposure to de-icing salts in a Swiss tunnel, and after 10 years exposure to a marine zone simulation in Japan. This paper will show that the use of a silane hydrophobic impregnation can be an effective way to reduce the risk of corrosion for concrete structures, including structures exposed to chlorides in a marine environment, or from the use of de-icing salts in winter time.

To check the reproducibility of electrochemical impedance spectroscopy (EIS) measurements, 19 laboratories have performed round-robin (RR) testing on EIS using various instruments and three different systems: a dummy cell, and two electrochemical systems of practical interest in the nuclear corrosion domain. The general conclusion drawn from the tests performed with the dummy cell is that the actual commercially available instruments for EIS measurements are suitable to produce good quality data. Differences in the EIS diagrams for the tested electrochemical systems were observed and discussed. This RR exercise, involving for the first time a large number of laboratories, shows that intrinsic scatter (large or small) is present in the impedance data and that reproducibility should be readily checked. While EIS is an excellent technique for investigating the kinetics of electrochemical systems, great care has to be taken on planning and conducting the experiments.Recommendations are given in this paper to help obtaining reliable EIS results.

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