Corrosion Pitting

 

Caused by steel's contact with water, corrosion pits are the are the product of rust. Oftentimes the pits will follow a water pattern - for instance, if water pooled in the bottom of the coil laps. Exposure time (the coil sat for a year) and exposure level (the laps were loose and it rained everyday) are the two biggest factors for corrosion pitting, but they can also occur quickly and when there is no evidence of exposure to water. Dew, high humidity, and latent water from the hot strip mill can cause corrosion, and any contact with salt water will increase corrosion exponentially.