Abstract
Hard chromium, electrochemical deposited, is a widely used and established coating solution for surface protection against wear and corrosion as well as for decorative applications. Due to the possibility to coat bulk goods also, this technique is well suitable to protect small pieces and mass-produced goods. However, the most disadvantage of that technique is the appearance of highly carcinogenic hexa-valence chromium. Because of human health and environmental aspects the replacement of this coating technique is more and more required. At least for bigger parts with larger surfaces H(igh) V(elocity) O(xy) F(uel) -spraying can already produce competitive coatings to galvanic hard chromium with equal or even better properties. Especially thermal sprayed carbide coatings with in terms of corrosion resistance tailored metallic matrices offering the best potential to replace hard chromium in various applications. Beside of the material properties also the spraying conditions have essential influence on the corrosion resistance of those coatings. The present paper will give an overview of different carbide containing materials for HVOF-spraying and their properties with special respect to the replacement of galvanic hard chromium. The closest attention will be on the corrosion resistance of HVOF-coatings of those materials in different aqueous solutions compared with hard chromium. For a liquid fuel high velocity spraying system also the trends will be shown in which way the spraying parameters are influencing the general corrosion behaviour of such coatings. Those tendencies by conviction of the authors are also transferable to other HVOF systems.