Influence of a static magnetic field on the protective ability of chromatic conversion coatings on zinc

Zinc coatings submitted to a Cr VI-based passivation treatment without and with magnetic field were studied. The influence of the static magnetic field remains when solutions are pre-treated in a magnetic field and then chromating is carried out (the so called the “memory” effect). Morphological investigations of the chromate conversion coating were performed using scanning electron microscopy (SEM). Distribution of elements in the chromate conversion coating was studied by X-ray photoelectron spectroscopy (XPS). The corrosion protection properties were determined by measuring the time dependence of the potential of the chromated zinc sample during a galvanostatic anodic pulse for a suitable solution. It has been shown that owing to pre-treatment of the initial chromating solution with the 0.5 T magnetic field the corrosion resistance according to the neutral salt spray test increases from 200 up to 400 h.