b'FOGHORNFOCUS: OPERATIONSiron-zinc layers to the steel, providing excellent abrasion re- flame spraying or electric arc spraying. Flame spraying uses sistance, with the layers becoming an integral part of the steelan oxy-acetylene torch to melt a zinc wire or powder that is rather than just a surface coating. continuously fed into the flame. A stream of gas, generally Another unique characteristic of the hot-dip galvanizedcompressed air, then propels the molten metal droplets in the coating is the uniform anddirection of the steel surface. complete coverage of allApplying thermalIn arc spraying, two zinc surfaces. During the met- sprayed Zn-15%Alwires are brought together allurgical reaction in thealloy above andat an angle and an imposed below the waterline kettle, the iron-zinc layersto a 70m ship.voltage difference between grow perpendicular to allPhoto source:them creates an electric arc surfaces, ensuring thatwhich melts the ends of both edges and corners have thewires. A gas flow, of either same coating thickness ascompressed air or a special flat surfaces. Additionally,gas, then atomizes and because hot-dip galvaniz- propels the molten metal ing is a total immersiondroplets toward the steel process, all interior surfacessubstrate. of hollow structures and recessed areas of complex piecesThe thermal sprayed zinc coating is produced by are coated.This complete, uniform coverage of all surfacesimpacting semi-solid droplets on a roughened steel surface. ensures that areas where corrosion commonly starts areThe coating thickness is dependent on the time of spray and protected with zinc. Since hot-dip galvanized coatings mustproduces a metallic layer with properties similar to solid zinc. be factory applied, weather conditions are not important forAlthough pure zinc was the first corrosion-resistant thermal coating quality, however steel structures are limited to thespray coating to be applied to steel nearly 100 years ago, a size of the galvanizing kettle.zinc-15% aluminum alloy provides superior corrosion pro-Thermal sprayed zinc coatings can be applied by eithertection and is now the coating of choice for ships. Thermal KEEPING BAY AREA FLEETS IN SERVICE FOR OVER 40 YEARSBay Ship and Yacht makes it a priority to per-form on-time, quality service for all vessels. We are a full service shipyard cosistently serving Al- 5 1 0 . 3 3 7 . 9 1 2 2 ameda, San Francisco Bay, the west coast andwww.bay-ship.com the worlds maritime industry for over 40 years. A l a m e d a , C AJUNE 2020FOGHORN 19'