HMDSO-Based Thin Plasma Polymers as Corrosion Barrier Against NaOH Solution

Jaritz, M. and Hopmann, C. and Wilski, S. and Kleines, L. and Rudolph, M. and Awakowicz, P. and Dahlmann, R.

Volume: 29 Pages: 2839-2847
DOI: 10.1007/s11665-020-04821-x
Published: 2020

HMDSO-based films with excellent corrosion barrier properties against strong alkaline solutions were deposited on chemically non-resistant SiOx barrier coatings, which were previously applied on polished gold-coated Si-Wafers and PET films for coating analysis. The plasma process parameters are seen to have a strong influence on the achievable corrosion barrier properties of the plasma polymers. Coatings, which were applied in a pulsed microwave plasma with low mean power input, exhibit a substantially higher resistance against NaOH aqueous solution in electrochemical tests than those applied in higher energy plasmas. An analysis of the coatings revealed that the great difference in chemical resistivity of the investigated coatings can be explained by their chemical composition as well as their nano-porosity and surface topography. XPS measurements indicate that a higher organic content in the films contributes to their chemical resistivity. FTIR measurements showed that an ordered Si-O-Si network with methyl groups, which promote steric shielding, lead to superior corrosion resistance. Furthermore, a correlation of protective performance and nano-porosity was found in cyclic voltammetry measurements. Coatings with good corrosion protection proved to be initially pore free and even after 30 min of exposure to NaOH, an open pore surface of only 2% can be measured. Finally, measurements of the oxygen transmission rate (OTR) of coated PET substrates showed that the barrier of a coating system comprising a non-resistant barrier layer and a protective top coat can withstand up to at least 90 min of exposure to hot NaOH solution without significant loss in barrier performance. After this, the barrier of the system is gradually reduced. To slow down this reduction process, a multilayer approach proved to be effective. © 2020, ASM International.

« back