The effect of sand abrasion in seawater has been investigated but is difficult to quantify. Sand loadings of less than 200ppm rarely damage good protective films on copper-nickel alloys. Very fine sand (<0.05 mm) loadings are tolerable up to about 1000ppm. Larger diameter sand particles tend to be increasingly abrasive to the film in the 200-1000ppm range. The 70-30 alloys have somewhat greater tolerance for sand. For sand loadings of 1000ppm and for larger particles of sands in the 200-1000ppm range, the 2% manganese, 2% iron, copper-30% nickel alloy, C 71640, has proven very resistant. In fact, the alloy was originally developed to combat sand erosion at Uskmouth Power Station in the UK.