Steel corrodes faster in the Gulf than almost anywhere. High humidity, salt-laden air near the coast, large daily temperature swings and intense UV combine to attack both the steel and the coating meant to protect it.
Classify the exposure before choosing anything
Protective coating standards classify environments by corrosivity, and the category drives the entire specification. Broadly:
- Inland, dry, sheltered — moderate. A conventional system performs well.
- Industrial or urban with pollutants — high. Needs a more robust build.
- Coastal, with chlorides — very high. Chlorides penetrate and drive corrosion under the film, so the system and preparation both have to be better.
- Immersed or buried — its own category, with its own rules.
Specifying a system without naming the category is guessing, and the guess is usually optimistic.
Preparation sets the ceiling
No coating outperforms the surface it was applied to. For structural steel that means abrasive blast cleaning to a defined standard — commonly Sa 2½ — with a surface profile suited to the primer. Two details matter especially in this region:
- Soluble salts. Blasting removes visible contamination but not chloride left on the surface. Coating over it traps the salt, which draws moisture through the film and lifts it. Where chlorides are likely, test for them and wash before blasting.
- Blast profile. Too shallow and the primer has nothing to key into; too aggressive and peaks are left proud of the film.
Build the system for the category
A typical high-corrosivity system runs a zinc-rich primer for galvanic protection, an epoxy intermediate for barrier thickness, and a polyurethane topcoat for UV and colour stability. Each layer does a different job — substituting one for a thicker coat of another does not work.
Total dry film thickness is the specification, and it must be measured and recorded. Without records there is no way to demonstrate what was applied.
Details fail first
Corrosion starts where the coating is thinnest or the geometry is awkward:
- Edges and corners, where film pulls thin — stripe coating these by brush before the main coat is standard practice for a reason.
- Bolted connections and faying surfaces.
- Welds, which need slag and spatter removed before coating.
- Drainage traps where water sits rather than running off.
Maintenance beats replacement
A coating inspected on a cycle and touched up locally lasts decades. One left until visible rust means blasting and recoating an entire structure, at many times the cost. Inspection is the cheapest line in the whole programme.
Where BK Services fits
Anti-corrosion coatings for steel structures, tanks and process equipment sit inside our construction and industrial finishing division, together with the fabrication and welding those structures need. Related reading: choosing process pipe material.
Tell us what needs protecting and we will survey and specify it.