Steel damaging in flowing mortar

The paper reports the results of an experimental research devoted to the study of the damage mechanism of steel in contact with fresh flowing cementitious mixtures. It focuses on the damage caused by both erosion and corrosion. Weight-loss tests, potentiodynamic tests and electrochemical impedance spectroscopy tests were carried out on stationary and rotating cylindrical/disk electrodes, on steels with different hardness, composition and microstructure ranging from carbon steel to manganese steel and stainless steel. The electrochemical tests were performed in fresh fluid mortar designed to grant sufficient workability retention up to 24 h. The specimens were observed after exposure by means of scanning electron microscope to evaluate damaging morphologies. The effect of rotating speed on damage and corrosion mechanisms is discussed in the present investigation. It was noticed that the corrosion contribution to the total damage was negligible at high rotational speed due to prevailing erosion. The results point out that corrosion rate rises with the rotational speed but it remains determined by the anodic process and re-passivation kinetic of the steel in the alkaline medium, without reaching conditions of oxygen-limiting current density.