Influence of steel gauge on the microstructure and corrosion performance of zinc alloy coated steels

Zn–4.8 wt% Al coated steels exhibited a polynomial increase in Zn loss from the cut edge with increasing steel gauge for weight loss and SVET Zn loss in 0.1% NaCl in contrast to a linear increase observed for hot dipped galvanised (HDG) steels. Increasing steel gauge decreased nucleation and increased growth of Zn dendrites for Zn–4.8 wt% Al coated steels. SVET data showed larger Zn dendrites associated with thicker gauges produced more damaging anodes than small dendrites on thinner samples. A polynomial relationship was observed between dendrite size and Zn loss suggesting that microstructure influenced Zn loss in unison with the increased cathodic activity on thicker steels.