Although most of the underwater-applied coating work was conducted 

 with seawater, deionized water and freshwater were also used in one brief 

 test to determine if the paints could be used in these waters at 70 F. 

 Formulation 101-19 was brush-applied to pairs of sandblasted steel 

 panels in tanks of deionized water, tap water, and seawater. In all 

 cases the coating was easily applied. After curing overnight, one panel 

 from each pair was wiped with a cloth saturated with a 50/50 mixture of 

 methylethyl ketone and toluene in order to remove any surface film such 

 as might be formed from amine migration to the surface. These panels 

 were then returned to their respective tanks, and all six panels were 

 topcoated with 101-19. The unwiped panels in the deionized and tap 

 water tanks were noticeably more difficult to coat than the others. 

 After curing underwater for 1 week, the bonding strengths of the paints 

 on each panel were determined as previously described; the results of 

 these tests are shown in Table 4. Although the unwiped panels in the 

 deionized and tap water tanks were more difficult to topcoat, the topcoat 

 bonded as well as or better than the wiped panels. 



FIELD SURFACE -PREPARATION TESTS 



A small field test was conducted at Port Hueneme on steel panels to 

 determine the effect on bonding strength of different methods of prepar- 

 ing their surfaces for underwater painting. Six sandblasted'^ steel 

 panels (2-3/4 inch by 6 inch) were corroded to a similar degree by 

 exposure for 8 days in a 5% salt spray cabinet. They were then secured 

 in place on a wooden specimen holder (Figure 1 ) and treated with different 

 methods of surface preparation as follows: 



Treatment 1 - Waterblasted above water at 10,000 psi and 10 gpm 

 (Figure 2) 



Treatment 2 - Waterblasted underwater at 10,000 psi and 10 gpm 

 (Figure 3) 



Treatment 3 - Waterblasted underwater at 8,500 psi and 10 gpm 

 with 16-30 mesh copper slag abrasive injected 



Treatment 4 - Manual wirebrushing underwater 



Treatment 5 — Sandblasting above water (accepted optimum surface 

 preparation procedure) 



Treatment 6 — Uncleaned control 



After cleaning, the panels given treatments 1, 2, and 4 had a 

 similar crudely cleaned appearance (Figure 4), while those given Treat- 

 ments 3 and 5 had a white metal appearance. 



Steel Structures Painting Council Surface Preparation No. 5. 



