Question

Describe a procedure for the repair of paint damaged areas on a vessel's hull.

State FOUR methods for dealing with surfaces usually inaccessible for painting due to the hull blocks in drydock.

Outline the problem that occur with self polishing copolymer paints when a vessel is at anchor for long periods or proceeding at reduced speed.

SOLUTION.

The effectiveness of any re-coating of a damaged paint surface is dependent upon the
preparation. If the damage is localised, hand preparation would be suitable. This would involve: Removal of oil and grease; Cleaning of salts (spray); Preparing the surface using a chipping hammer and wire brush; Grinding out local damage.

More widespread damage will require abrasive blasting, which is the most effective method of steel preparation.

To be most effective, paint priming of the surface should occur immediately after preparation and should be compatible with the subsequent finishing coats of paint. Anti fouling paint is required for underwater surfaces and an impact resisting coating is required for areas susceptible to damage/erosion.

(b)

(i) Remove top of blocks individually, apply coatings and replace the blocks.,
(ii) 'Fleet' the vessel - float and re-dock immediately in a different position.
(iii) Coat in-water with an approved underwater paint system.

(iv) Ignore the unpainted areas, so that corrosion and anti fouling protection is effected by the cathodic protection system and existing anti fouling paint coating. Amend the drydock block plan for the next docking so that previously covered areas are exposed.

(c) The film is designed to ablate at a certain speed to expose fresh biocide and 'polish' the surface. This is not achieved when die ship is at anchor for long periods, thus heavy fouling may occur. If such fouling were to occur then the self polishing and hence anti-fouling effect would be nullified when the vessel were on passage.