Influência do passo de activa？？o da deposi？？o por plasma nas propriedades barreira de coil coating

surface properties of organic coatings, like scratch and abrasion resistance, gloss, hydrophilic and hydrophobic nature and easiness to clean, among others, can be modified by deposition of thin films using plasma polymerization processes. the properties are obtained with expense of the corrosion protection properties of the coating, since degradation is induced by the plasma polymerization conditions. previous studies showed that the degradation occurs mainly during the activation step of the plasma polymerization process. the activation step is used to clean the surface and to enhance the adhesion between the two layers so it is necessary to create a point of compromise where the minimal influence to the barrier properties is achieved without impairing the plasma polymer film long term resistance. the present work aims the clarification of the degradation mechanism of the coil coating during the plasma activation processes. different plasma reactors, working gases (argon, oxygen and air) and time of exposition activation step were studied. samples degradation was monitored by electrochemical impedance spectroscopy and surface analysis. clear dependence between the activation gas used and time of activation with reduced barrier properties was encountered. one of the major influences is observed when oxygen is used. this is explained by the formation of atomic oxygen during the plasma treatment that leads to the formation of carbonyl groups, showing higher degradation for longer activation periods.