It is known that nutrients can increase corrosion loss and increase the severity of pitting corrosion, both for short and for longer term exposures. However, the quantitative relationships involved are not well-defined nor is the effect of high nutrient loadings well-understood. Nutrient loadings for natural coastal seawater can occur through run-off of excess fertilizers and waste products from adjacent agricultural lands, either as a result of fertilizers applied for crop improvement or as a result of animal husbandry. It is known also that relatively high amounts of oxidised nitrogen, such as in nitrites, can inhibit corrosion. Herein a report is given of observations for highly polished mild steel coupons 25 mm x 25 mm in size exposed to different concentration levels of fertilizer. The coupons were exposed continuously for up to 546 days to low velocity streams of natural seawater in 200 litre tanks. There was no intervention in the first tank but the other two were dosed periodically with agricultural fertilizer, with the third tank being dosed at twice the rate of the second tank. For the first three months corrosion losses were similar in all three tanks but then began to diverge. After about twelve months corrosion loss in the second and third tank was around 90% and 75% respectively of that observed in natural seawater and this continued for the rest of the experiment.
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