Polymeric substrates have to be severely cooled during the plasma spraying process to limit detrimental effect due to the high heating flow from the plasma jet. The « Atmosphere and Temperature Controlled process » (ATC, patented by CEA) was used to maintain the substrates near room temperature. However, the PET substrates might undergo some superficial modifications which could result from the plasma jet heating and particle heating at the impact. This paper deals with a study of chemical modifications in PET as a function of surrounding atmospheres during plasma processing. Aluminum coating adhesion was determined using tensile tests.