Rust Spots under Paint
on Steel Surfaces

Back to Paint Film Defects

Q:  After inspection of the ship, we are experiencing rust spots on a brand new marine vessel .  Our customer doesn't want to take delivery of the vessel unless we can show that corrosion will no longer take place.

A:  It appears that the paint film may not be thick enough to completely cover all of the peaks and valleys that have been created by the abrasive blasting process.  The peaks that are exposed or have insufficient coating coverage have begun to corrode.  I would suspect that performing paint film thickness tests in the areas that are showing rust would indicate insufficient paint coverage over the blast profile.

In new construction, the marine industry norm for surface prep for paint application is to abrasive blast the surface in accordance to SSPC (The Society for Protective Coatings) specification process SSPC-SP 10 to near white metal or to SSPC-SP 5 white metal.  The surface should have been cleaned then abrasive blasted to a minimum profile of 1.5 mils, and the coating system should be applied thick enough to sufficiently cover all the peaks and valleys to properly protect the steel surface against corrosion.

We are certified under the Naval Sea Systems Command (NAV-SEA) to perform these types of inspections on marine vessels.  We are available to travel to the location of the vessel, perform various tests in order to confirm that all required specifications for quality and application have been satisfied; we are also able to assist in identifying proper repair specifications.

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