Long-term atmospheric corrosion properties of thermally sprayed Zn, Al and Zn–Al coatings exposed in a coastal area

• We examined long-term atmospheric corrosion resistance of thermally sprayed coatings.
• The 100 μm thermally sprayed coatings showed high corrosion performance.
• The corrosion products formed on the thermally sprayed coatings were identified.
• The distribution of elements of S and Cl was observed in the corrosion products.
• The surface structures of thermally sprayed coatings were proposed.

The long-term atmospheric corrosion properties of thermally sprayed Zn, Al and Zn–Al coatings have been evaluated using an electrochemical impedance measurement and several analytical techniques. All the thermal-sprayed specimens with 100 μm coating thickness have protected the steel substrates. In case of the Zn–Al coating, the red rust was not observed regardless of the coating thickness. The corrosion products were identified by the XRD analysis. Preferential dissolution of zinc was observed on the Zn–Al coating by EPMA analysis. The electrochemical impedance results provided an insight about the surface structures of each thermally sprayed coating.