Effects of pretreatment on the structure and properties of electroless nickel coatings
The pretreatment process can significantly affect the corrosion resistance of electroless nickel (EN) coatings. One of the most important reasons is that different pretreatment processes can give different surface morphologies of the substrate. The scanning electron microscope (SEM) and the scanning tunneling microscope (STM) have been used to investigate the structure and properties of EN coatings in the as-plated condition for various deposition times, in relation to different mechanical/chemical pretreatment processes. The morphology of the substrate surface is found to be a key factor in control of the porosity of EN coatings. It can significantly affect the formation of EN deposits, not only in the early stage but also in the morphology/ structure during the continued growth of the deposit
Building a platform for growth
Summary Electroless nickel offers the engineering community a technology that is as reliable as it is diverse in meeting today's challenging applications. We must remain aware that current EN technology has limitations and maximizing deposit performance requires a cooperative effort between supplier, applicator and the end user. Success of electroless nickel in the future will require a strong commitment from these partners to advance the technology and the continued evolution of the EN family tree.
The oxidation of electroless Ni-B and Ni-P coatings in air at 800 to 1000°C
The oxidation of electroless Ni-B coatings in air at 800 to 1000°C has been determined by kinetic, X-ray diffraction, and microscopical methods. Some data have also been obtained on the oxidation of Ni-P coatings, the oxidation of nickel, and the effect of Na2SO4 on the oxidation process. All kinetics followed the parabolic oxidation law and the rate increased in the order spectrographically pure nickel, commercially pure nickel, Ni-B, and Ni-P, with the Ni-P oxidizing approximately 1000 times faster than the spectrographically pure nickel. Fine surface deposits of Na2SO4 greatly increase the oxidation rate of all materials except the Ni-P coatings which appear to be immune to hot-corrosion. The nature of the oxidation processes are discussed.