Introduction of hull section painting method for newly built large ships

Steel Surface Pretreatment

In order to last for a relatively long ship construction period, the surface of the steel must first be treated and a maintenance primer should be applied. Then apply the maintenance primer to the steel for lofting, blanking, drilling, etc. to add segmented hulls.

Steel materials for ships are subjected to strict surface treatment. The general procedure is: brush off the oil stains, garbage and accumulated water on the surface of the steel plate, perform leveling, preheat and dry, remove surface moisture and moisture; It is usually required to reach the level of SA 2 and 1/2 (Swedish standard S 59100), the surface roughness of the steel plate should be between 45 microns and 75 microns, the maintenance primer should be sprayed, and the paint film thickness should be between 15 microns and 25 microns. If painting is carried out in the workshop, far-infrared dry operation can be used if conditions permit. The paint film of the maintenance primer should have an anti-rust ability of more than 6 months, and have excellent solderability, recoatability and cathodic protection. adaptability. (Related instrument: roughness Tester)

Chemical derusting is also often applied to thin steel plates in shipyards. The procedure is as follows: degrease the steel plate in the lye tank, rinse it with hot water, put it into the pickling tank to remove rust, wash it with water, neutralize it, then phosphate it, and finally coat it with antirust paint.

small close repair

After the steel plate and section steel coated with maintenance primer are mechanically treated, they are small closed and welded into small sections. The surface of the original maintenance primer paint film is damaged by the processing process, and it is necessary to immediately use pneumatic tools for surface treatment and repair the maintenance primer. Small closed sections are usually built indoors, and touch-up primers are also done indoors.

Secondary rust removal and anti-rust paint

The subsections after small closing and repairing are welded together, and the sections of the hull after closing up in progress need to be derusted for the second time." The purpose of the second derusting includes cleaning oil, removing welding spatter, welding slag, and burnt paint. Film, remove newly generated rust, garbage, etc., and increase the roughness of the surface group.

It is better to carry out shot blasting treatment in a large shot blasting and painting workshop for secondary rust removal. Those who do not have the conditions have to use pneumatic grinding tools to remove rust. The derusting standard of the hull, superstructure exterior and main energy room polished by pneumatic tools shall meet the Swedish standard S13. The second rust removal generally requires painting on the same day of rust removal to avoid new rust. If the painting is carried out in the open air, it should be done before 3 pm to avoid affecting the quality of the painting due to condensation at night. Painting is mainly applied by high-pressure airless spraying.

Paint in sections

Before the subsections are closed and the ship is launched, the welded parts of the hull subsections and the damaged parts should be derusted and repaired and painted. All painted with anti-rust paint. For the bottom of large ships, the thickness of the anti-rust coating is about 250 microns. Widely used are high-build thixotropic coatings, mainly epoxy, chlorinated rubber and vinyl types. The hull is coated with the first topcoat on the anti-rust paint, and after natural drying, temporary coating is applied to the ship's name and draft marks. (Related instrument: drying time Tester)

Delivery and final painting

The exterior of the hull is fully rinsed with clean water, and after the damaged parts are repaired, the topcoat is sprayed on the entire surface to complete the removal of the mark. The total coating thickness of the hull is generally 250 microns to 300 microns. (Related Instruments: Thickness Gauge)