US Army Corps of Engineers
EM 1110-2-3401

5-8. Thermal Spray Selection for Zebra Mussel Protection

The zebra mussel is a freshwater bivalve that colonizes hard substrates. When present in sufficient densities, the zebra mussel can impact the performance of civil works structures and floating plants. Zebra mussels can impair structure performance by occluding narrow openings and small conduits such as may be found in condenser tubes, trashracks, sea chests, fire suppression systems, etc. Zebra mussels can also reduce the efficiency of floating plants and power plants by causing hydraulic drag.

Coatings are one means of preventing the attachment of zebra mussels to Corps structures. Thermal spray coatings containing zinc and/or copper have been found to be effective deterrents. Juvenile mussels will not settle on these metallic surfaces because small amounts of zinc and copper leaching into the water from the coating act as deterrents. The mussels are not actually killed but rather they sense the toxic chemicals in the water and do not attach themselves to these surfaces.

Thermal spray coatings containing copper such as brass, aluminum bronze, and pure copper should not be applied to steel substrates because they will not protect the steel from corrosion and may make it worse. Copper and brass thermal spray coatings can however be applied to concrete substrates to prevent zebra mussel fouling. Zinc and 85-15 zinc-aluminum alloy coatings are a better choice for controlling zebra mussels on steel as they also serve as anticorrosive coatings. Because of their lower material costs zinc and 85-15 zinc-aluminum are probably better choices for concrete as well, even though they are slightly less effective than brass and copper.

Zinc containing coatings do not need to be registered with the EPA. Zinc is a relatively weak aquatic toxin and is an even weaker mammalian toxin, and as such, no effects on nontarget organisms should be anticipated with its prophylactic use as a zebra mussel deterrent.