Experimental investigation of the damage of carbon steel sheets coated with anticorrosion coatings under simulated lightning currents

In order to get further insight into the damage characteristics and the damage mechanism of coated metal under simulated lightning currents, lightning damage experiments on coated and uncoated Q235B steel sheets were conducted under the 30/80 μs impulse current and 2kA 2ms rectangular current simulating the lightning first return stroke current and the intermediate current respectively. The macroscopic surface morphologies and the metallographic microscopic cross section morphologies of the damage zones were observed. The damage diameters of the damage zones were measured. Based on the experimental results, damage characteristics of coated and uncoated metal sheets under the 30/80 μs impulse current and 2kA 2ms rectangular current were concluded and compared. The influence factors on the damage characteristics were analyzed. The work showed that on coated metal sheets inflicted by the two types of simulated lightning currents, pits formed duet to the melt and decomposition of coatings under the thermal effect of the arc attachment points. The pit provided a physical constriction to prevent the ejection of molten metal, thus the damage diameters of coated metal sheets were smaller than uncoated metal sheets and it increased slightly with the amplitude of the 30/80 μs impulse currents rising whilst that on the uncoated sheet increased obviously. Because of the difference on current durations, the coatings would aggravate the ablation effect of metal under 2kA 2ms rectangular currents but play a protective effect for metal under 30/80μs impulse currents.