Corrosion protection of cold-rolled steel by zinc-rich epoxy paint coatings loaded with nano-size alumina supported polypyrrole

High porosity and intense galvanic function related low electrolytic barrier profile and fast delamination of zinc-rich paints (ZRPs) are addressed by the utilisation of intimately structured, highly dispersed, polypyrrole (PPy) deposited alumina particles (PDAPs) embedded zinc-rich hybrid paints. The more globular but less-packed structure type PPy-contained water-solvent-prepared PDAPs-composited hybrids comprising spherical zinc pigment at 70 wt.%, provided moderate galvanic function with enhanced electrolytic barrier properties. In addition, the less globular structured but well-packed PPy-comprised aqueous ethanol-solvent-prepared PDAPs-composited hybrid coatings indicated highly efficient suppressed galvanic function and improved barrier properties, realising solid performance improvement over conventional ZRPs in immersion and salt-spray chamber tests. Furthermore, the application of highly dispersed PDAPs at a content of 3.2 wt.% while PPy incorporated into zinc-rich hybrids at 0.16 wt.% is proposed to result in emerging additional functionalities increasing long-term anticorrosive performance of ZRPs by inhibiting sacrificial and self-corrosion of zinc and scavenging oxidative radicals thereby hindering oxidative degradation of the organic binder.

► Various polypyrrole deposited nano-sized alumina particles (PDAPs) were prepared. ► Relevant changes in the physicochemical properties of PDAPs were found. ► Hybrid paints were formulated at contents of 3.2 wt.% PDAPs and 70 wt.% zinc. ► Organic-mixture prepared PDAP-based hybrid exhibited solid improvement over ZRP. ► Hybrids feature enhanced barrier and moderate galvanic protective function.