The particles would have to be extremely small to not fall out of suspension, so I don't think they'd be very abrasive.
The thickness of the viscous part of the boundary layer in water is maybe 0.1 microns (if the water is moving at 10 m/s). Particles smaller than this would be slowed before striking the surface. If the particles are making the liquid more viscous the viscous part of the boundary layer will be proportionally thicker.
