Very often coatings are multi-layer constructions. The first layer on the (pretreated) substrate is also called primer, pre-coat or undercoat. This has firstly the task of ensuring the adhesion of the coating system to the substrate, secondly it must provide a good adhesion base for the subsequent layer and - especially in the case of metals - it usually still fulfills important functions with regard to corrosion protection.
Primers do not have a uniform chemical nature, but are formulated, selected and used according to the function to be performed. For example, these include thin polymer layers, specially formulated coatings or systems based on silicon, titanium or zirconium compounds.
A special type of primers are etching undercoats, which attack the metallic substrate moderately and bind firmly in the course of this. An example of such adhesive agents are the polyvinyl butyral-based primers, which have been known for a very long time and contain phosphoric acid.
Primers for plastics that are difficult to coat - such as polyolefins or PP/EPDM - often contain chlorinated polyolefins, because these already generate a certain adhesion on polyolefin surfaces even without activating pretreatment. In combination with a corona or flame treatment, very adhesive coatings can be realized.
Primers must always be considered and selected as well as formulated in the context of the overall requirements for the coating composite. These includes substrate, subsequent layers and coatings, requirement profile for the coating composite and technical production conditions.
We are pleased to support you in the selection, formulation and application of primers for your coating application and are available for your questions and comments.