INTRODUCTION 



The Navy has miles of steel waterfront structures situated in very 

 corrosive environments. The protective coatings on these structures are 

 subject to accelerated deterioration both by the environment and by 

 impact and abrasion. While deteriorated coatings in dry areas are 

 relatively easily repaired, those located between tides or underwater 

 have in the past been very difficult, if not impossible, to repair. 



In 1962, the Shell Chemical Company offered coating and adhesive 

 manufacturers a two-component epoxy formulation designed to cure on 

 either dry, damp, or underwater surfaces. Shortly thereafter several 

 coating manufacturers began marketing products (generally called splash- 

 zone compounds) that were prepared directly from, or were variations of, 

 this formulation. These products were so viscous that they had to be 

 applied by the palm of the hand at 1/8 to 1/4 inch thicknesses rather 

 than by a brush or roller at the usual paint thicknesses. The Navy 

 investigated [1-9] the use of these products and prepared a specification 

 for them. Because they were difficult and costly to apply, the Civil 

 Engineering Laboratory (CEL) conducted the present investigation into 

 lower viscosity coatings that could be applied underwater by brush or 

 roller. 



MATERIALS INVESTIGATED 



Most of the commercially available coatings that can be applied by 

 brush underwater have been laboratory- tested by CEL. The vast majority 

 of these have been solvent-free epoxies, but some polyester formulations 

 have been tested. The polyester materials have generally been easier to 

 apply, but they cure much more slowly and tend to be soft and more 

 easily damaged. Because the epoxy coatings have been more durable, this 

 CEL investigation was limited to them. Of the Navy-devised epoxy formu- 

 lations, those utilizing amine-adducts as curing agents showed the most 

 promise. Two of the more promising basic formulations, 101 and 102, 

 were prepared by a coating supplier in batch quantities. The composition 

 of these formulations is shown in Table 1 . Table 2 shows several varia- 

 tions that were made in the curing agent to improve such properties as 

 wetting of substrate (101-19 and 102-19) and rate of curing (101-5 and 

 102-5). 



'^ MIL-P-28379 (YD), Plastic Compound, Epoxy-Polyamide, Marine Splash- 

 Zone Application. 



