Influence of the bronze powder filler on the adhesion of epoxy compound to aluminum bronze

Abstract

The tests to determine the adhesion of epoxy compound K-153, containing different amount of bronze powder, to aluminum bronze are carried out. As the bronze powder the filings, which are obtained by filing the rolled rod of bronze BrAZhNMts9-4-4-1, are used. The conventional size of the bronze particles amounts to 18 μm. The epoxy compositions are applied over the plates made out of BrAZhNMts9-4-4-1. The mentioned bronze is chosen as close analogue by composition to bronze BrA9Zh4N4L, used to cast ship propellers. The plates thickness is 4…5 mm, and the plates dimensions in plan are equal to approximately 50 by 100 mm. Before being coated the plates are ground with abrasive paper of different grain to obtain the arithmetical mean deviation of the surface profile equal to 0,5…0,900 μm. Coating the plates and aging the coatings are produced at temperature of 19±1 о С and ambient air relative humidity of 50±5 %. The average thickness of the coating amounts to 2,1 mm. The experiments are conducted after keeping the epoxy coating during 7 days. The tests are carried out according to the scheme, regulated by the GOST 32299-2013 "Paint materials. Pull-off test for adhesion". According to the scheme, metallic cylinders of the 19 mm diameter are stuck to the coating; preliminarily the spots of sticking are processed with abrasive cloth and solvent. Then the circular cuts are made in the coating around each cylinder and the cylinders are pulled off under the force directed perpendicularly to the coating, and the peel strength is recorded. The addition of bronze powder into the epoxy compound does not affect the peel strength that is the precipitation of the bronze particles in the epoxy compound during its hardening does not result in the decrease in the contact area of the epoxy resin with the bronze surface. This conclusion is confirmed by the calculation estimation: the calculated thickness of the resin layer in between a bronze particle and the plate surface after the completion of resin hardening is three orders of magnitude greater than the diane resin molecule size. It means that epoxy resin viscosity is too high, and the size and the mass of the particles are too small in order for the squeezing the resin, even partial, from under the particles takes place during the slow precipitation of the particles.