A protective film layer is formed over aluminum coating with Physical Vapor Deposition (PVD) processes to ensure the resistance to environmental factors of the sub-components that include headlight reflective surfaces. Increasing endurance of the sub-components to environmantol factors is demanded with the development of automotive quality demands. In this study, Hexamethyldisiloxane (HMDSO) monomer releasing system that is used to form a protective film layer in PVD processes, has been optimized for releasing homogenously through the pipeline to the vacuum chamber by using finite volumes method. In addition, for uniform distribution of the HMDSO monomer release before polymerization into the vacuum medium, the substrate's jig revolution mechanics were analyzed by Computational Fluid Dynamics (CFD) simulations and the results were verified by experimental applications. The Sodium Hydroxide (NaOH) resistance of parts in various regions of the vacuum chamber was between 350-550 seconds before the study. However, it has been carried to over 1000 seconds for all regions after the optimisation process. Thus, ultimate life of the part and parts' resistance to environmental factors are increased. Thanks to this study, the desired quality requirement for the sub-components that are coated in the vacuum chamber with a volume of 2,84 m(3) was provided for all parts in different regions within the chamber. There is no need for new single planet machines with 1,13 m(3) volume vacuum chamber and production output that was obtained with the bigger chamber machine is doubled. No similar works have been found that are carried out by suppliers or in the literature.