A study on the effects of the process parameters of polymerised HMDSO using RF-PECVD in corrosion protection applications

Abstract: In this master thesis the effects of the process parameters of pp-HMDSO were studied in the application of corrosion protection of an Al surface. The method for polymerising the HMDSO vapour was RF-PECVD. The following process parameters were studied: RF-power, flow of HMDSO, Oxygen as reactive gas, Ar as inert gas, the effect of applied bias voltage, as well as Ar etch as pre-treatment and subjecting the film to a pure O2 plasma as post-treatment. The results were a prolonging of the total decay time of the Al film when subjected to a 1M NaOH solution. The decay time increased from 5-20s for an unprotected Al film to 140min for the best pp-HMDSO coating. SEM/EDX, XRR, L'a'b' were used when analysing the pp-HMDSO films. The best performing coatings were tested on reflectors and passed the industry standard test of being subjected to a 0.1M NaOH for 5min without visible corrosion or decay.