Progress in the development of a pyrrole-based silane primer for corrosion protection of Al alloys

A non-chromate, direct-to-metal treatment for corrosion protection of several Al alloys (AA) has been previously developed in our group by using a pyrrole-based silane (PySi) in methanol:H2O 95:5. The impressive performance of PPySi films, combining both barrier and anodic protection, in comparison to simple polymethylsiloxane and polypyrrole coatings, is determined by the high degree of crosslinking through both silanol groups condensation and pyrrole rings a-a’ linking. This “double” crosslinking provides closedpacked, compact PPySi well-adhered to Al substrates. This work reports on improvements of PySi-based formulation in terms of solvent nature and water content, where low VOC tertiary butyl alcohol (tBuOH) was chosen. Reference coating with octylsilane (OctSi), whose molecule size is equivalent to that of PySi, was also studied. Polypyrrole (Ppy) coatings were electrochemically synthesized, following reported method. PPySi structural characteristics as well as its corrosion performance support previous studies in terms of promising composite coating for corrosion protection of Al alloys.