The following provides details regarding the preparation, testing and classification of candidate paint coating systems for protection of ship ballast tanks.

　

 The tests may be carried out by any reputable and independent laboratory.

　

 Each coating product to be qualified shall be identified following the NORSOK standard, which specifies the following tests:

 The identification shall be carried out on the batch which is used for the pre-qualification testing and for subsequent samples to confirm the product actually used for the project is the same.

　

 This document considers hard coating systems with and without a zinc silicate primer.

　

　

　

 The test panels are cut to size from cold-rolled steel sheets, NS 37, and gritblasted to SA 2½, according to ISO 8501-1: 1988 (Swedish Standard SIS 055900), After blastcleaning and coating of the reserve sides, the front sides are prerusted in a salt spray chamber. The panels are exposed for about 18 hours - dried for 5 hours and slightly wirebrushed before next exposure. This procedure is repeated 4 times. The panels then correspond to Rust Grade C in ISO 8501-1: 1988.

　

　

 The rusted front sides of the test panels to be gritblasted to SA 2½ having a profile depth range recommended for the particular coating to be assessed.

　

　

 The application process to be carried out either at the Laboratory or manufacturer's site. Representatives from the paint manufacturer and laboratory must be present during the application process.

　

 A paint application from (see Figure 1) to be completed during application and must be signed by the representatives present.

　

　

 Application to be via airless spray and application data to be provided on product data sheet (see Figure 2).

　

 All panels to be cured in a ventilated room, at a temperature of 18-24℃, relative humidity between 40 and 60%.

　

　

 The dry film thicknesses (DFT) to be measured with a reliable electromagnetic instrument, calibrated on cold rolled smooth steel panels.

　

 In order to get a uniform procedure for measuring on all panels, templates are used.

　

 Nine measuring points are used on panels size 150mm × 150mm and 15 measuring points on panels size 200mm ×400mm.

　

　

　

 The test panels are cut to size from cold rolled steel, NS 37 and shotblasted with steel shot to SA 2.5. Surface roughness is 60-90Rmax measured with a reliable electronic surface roughness instrument. A low zinc shop-primer to be applied at 15-20 microns, measured on a plane steel panel according to NS 1913 (1977). The shop-primed test panels to be weathered for 14 days. Prior to application of paint coatings, the shop-primed surface is washed with tap water and spot tested for surface salts.

　

　

 Figure 4 shows a wave test tank which is mounted on a skid and can be cyclically tilted to create the wave movement in the tank. The cyclic tilting is set at a constant rate of 22-25 waves per minute.

　

　

 In each tank are mounted four test panels measuring 200mm x 400mm x 5mm: one in the top, one in the bottom, and two panels on opposite vertical sides. The reverse side of the panels are painted. On the front side the test products are applied.

　

　

 The tank is filled to 1/3 of its volume with seawater which keeps a temperature of 35℃. The top panel is heated to 50℃ for 12 hours and 20℃ for 12 hours. This is dine in order to simulate the heat from the sun's rays (12 hours at 50℃) under deck in top wing tanks, and a subsequent 12 hours at ambient night temperature.

　

 One of the vertical panels is cooled on the reverse side, giving a temperature gradient of approximately 20℃ through the coating. Such gradients have been found to be detrimental to many types of coatings, and this effect will simulate, for example, a cooled bulkhead in a ballast wing tank.

　

 The other vertical panel has no heating/cooling. The bottom panel has a fixed sacrificial zinc anode in order to evaluate the effect of cathodic protection.

　

 The test cycle is run for two weeks with seawater and one week empty. When empty, some seawater is left in the bottom to achieve a relatively high humidity in the tank. The level of the seawater is below the bottom panel in this period in order to simulate an empty tank with no effect from the anode. The three week cycle is repeated until the total exposure time is reached.