Corrosion of Zn under acidified marine droplets

Atmospheric corrosion of Zn under a variety of simulated marine aerosols was studied. In-situ monitoring of droplet pH, volume loss measurements, identification and distribution of crystalline and amorphous phases from corrosion under different droplets were used to understand the role of acidification on atmospheric corrosion of Zn. Results for various droplet chemistries are discussed in terms of initiation mechanism, phase distribution and surface morphology in conjunction with chemical equilibrium calculations. Zn exposed to sulphate containing droplets had relatively small corrosion rates and greater coverage with Gordaite as compared to sulphate-free droplets where coupons have relatively more coverage with Simonkolleite.

Research highlights
► Corrosion oxides are formed under highly acidic droplets.
► Agreement exists between pH measurements, chemical equilibrium and corrosion products.
► Three zones of oxide growth (centre, periphery and secondary spread) occur under droplets.
► Sulphate containing droplets are less corrosive than non-sulphate containing ones.