Ramanathapuram district has water on three sides, and the wind carries salt a long way inland. That airborne chloride settles on exposed steel, draws moisture out of the humidity, and sets up an electrochemical cell on the metal. Steel does not need to be splashed by seawater to corrode — a salt film and 75% relative humidity is enough, and we have both for most of the year.
So a specification that works in Madurai underperforms here. Standard enamel on an inland shed truss might last five years; the same enamel on a jetty near Pamban shows rust bleed inside twelve months. The difference is not paint quality — it is that the environment is doing something the product was never designed to resist.
Protective coatings answer that with a layered system. A primer that either sacrifices itself or passivates the surface chemically. An intermediate coat that supplies the film thickness and barrier. A topcoat that survives ultraviolet and keeps the layers beneath it intact. Each does one job, and skipping any of them shortens the whole system disproportionately.
The other half is surface preparation, and it matters at least as much as the coating. Steel blast cleaned to SA 2.5 gives the primer an angular profile to key into; hand wire-brushing leaves mill scale and embedded chloride behind, and the best epoxy made will disbond from it within a couple of years. Where blasting is not practical there are surface-tolerant products built for that compromise, and we will point you at them rather than sell you a specification your site cannot deliver.
