THERMAL DIFFUSION AS THE ALTERNATIVE OF HOT-DIP ZINC COATING FOR FASTENERS

During the investigation a quality of the thermal diffusion coating dedicated for anticorrosion protection of fasteners was assessed. Because of similarity of parameters and structures, properties of the inspected coating (thermal diffusion) were compared with effects get as a result of hot-dip galvanizing. Coatings were deposited in industrial conditions on flat samples and screws made of 23MnB4 steel. The corrosion resistance of coatings was measured by neutral salt test-NSS. The kinetics of the corrosion on flat samples was additionally determined basing on the computer image analysis. Microscopic examinations concerned the thickness, the structure and the state of the surface (roughness) of assessed coatings. Conducted EDS analysis allowed for comparing the structure of coatings with the theoretical model. It was stated that the thermal diffusion coating was admittedly less resistant to corrosion in the examined environment, but as a result of the further optimization of process parameters (duplex method) and the method of surface preparation the significant improvement in anticorrosion properties is expected.