What level of surface preparation is required for a steel structure in a marine environment?

For new steelwork, blast cleaning to Sa 2.5 is recommended. For maintenance, a thorough power tool cleaning to St 3 might be acceptable depending on the chosen paint system (Clause 4).

What is a typical painting scheme for a steel pile fully immersed in seawater?

A high-build coal tar epoxy system with a total DFT of 400-500 microns or a solvent-less epoxy system is recommended (Table 3).

How is the thickness of the paint checked on site?

Using a calibrated Dry Film Thickness (DFT) gauge. Measurements should be taken systematically across the surface to ensure compliance with the specified minimum thickness (Clause 7).

Can painting be done in high humidity?

No, painting should not be carried out when the relative humidity is above 85% or when the steel surface temperature is less than 3°C above the dew point (Clause 6.3).

IS 9077

: 1979

Code of Practice for Corrosion Protection of Steel Structures

CurrentFrequently UsedCode of PracticeBIMMaterials Science · Coastal and Marine Engineering

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This standard provides guidelines for the selection and application of protective systems for steel structures against corrosion, with a special focus on aggressive coastal and marine environments. It covers environmental classification, detailed surface preparation methods, various painting and metallic coating schemes, and inspection procedures.

Lays down the code of practice for the protection of steel structures against corrosion by various methods.

Quick Reference Values

Surface profile for blast cleaning (Sa 2.5)25-50 microns

Minimum zinc coating thickness for hot-dip galvanizing85 microns

Minimum total DFT for severe marine environment200-300 microns

Maximum salt contamination level before painting< 50 mg/m² as chlorides

Standard surface preparation grade for new construction in marine zoneSa 2.5

Practical Notes

Surface preparation is the most critical factor; over 70% of coating failures are attributed to inadequate surface preparation. Adherence to Sa 2.5 blast cleaning is paramount in marine zones.

Ensure compatibility between primer, intermediate, and top coats by consulting manufacturer's technical data sheets, especially when using products from different brands.

The environmental conditions (humidity, temperature, dew point) during paint application are as important as the surface preparation itself for achieving the desired coating life.