Variability of corrosion of mild steel coupons in tidal, splash and atmospheric marine environments

The corrosivity at a particular geographical location is often determined by material loss of mild steel coupons. It is known that there can be some variability with horizontal placement but little has been published on variability of corrosion losses for coupons in the horizontal direction. Herein results are presented for the corrosion loss of sets of nine mild steel coupons exposed for various periods up to 42 months in the mid-tide and marine atmospheric environments. Duplicate sets were exposed east-west and north-south. Generally, variability of coupon mass loss for those exposed in mid-tide conditions was less than 10%, whereas variability for those exposed in atmospheric conditions ranged from less than 5% to greater than 50%. Possible reasons for such large variations are given. Additionally it was found that coupons exposed in the east-west orientation corroded slightly more than those exposed north-south.