Adhesion and Corrosion Performance of Nanostructured Nickel and Cobalt-Based Coatings

Abstract Over the past two decades, nanostructured materials have been the subject of enormous interest. These materials get their name from the extreme small grain or particle size (5 nm to 100 nm) of their microstructure. It is well known that changing the grain size is an effective way to control the mechanical, physical, and electrochemical properties of polycrystalline materials. Accordingly, nanocrystalline materials with grain sizes less than 100 nm exhibit properties which are significantly different from the properties of their conventional polycrystalline counterparts. Resistance to localized corrosion attack such as pitting corrosion, stress corrosion cracking and intergrangular corrosion are some of the corrosion properties reported for these nanocrystalline materials. In addition, it has been shown that nanocrystalline materials possess ultrahigh hardness, tensile and compressive strengths as well as ultrahigh wear and erosion resistance coupled with low coefficient of friction as compared to their conventional polycrystalline counterparts. These characteristics make nanostructured materials strong contenders for high performance coating applications. This paper is divided into two parts. The first part provides a brief review of published literature on the corrosion behavior and mechanical properties of electroplated nanostructured coatings, particularly nickel, in terms of microstructural affects. The second part of the paper reviews the recent laboratory tests conducted at Saudi Aramco Research and Development Center to study the hardness, adhesion and corrosion performance of electroplated nanostructured nickel, Ni-P, cobalt and Co-P coatings.