acmm10.1108/acmmAnti-Corrosion Methods and Materials0003-5599Emerald Group Publishing Limited10.1108/acmm.1999.12846bab.004e-non-articleSecondary articleCorrosion USAcat-ENGGEngineeringcat-MEGMechanical engineeringMetal ARC-spray materials and methods01041999462© MCB UP Limited1999Arc-spraying, Coatings.peer-reviewednoacademic-contentyesrightslinkexcludedMetal ARC-spray materials and methods

Metal ARC-spray materials andmethods

KeywordsArc-spraying, Coatings

The US Army Corps ofEngineers Construction Engineering Research Laboratories (CERL) is testing metalarc-spray materials and applications to determine the best ways of protecting avariety of structures from electromagnetic effects.

Arc spray is a thermalspray method that involves heating metal to a liquid state with an electric arc.An air blast is used to break down this molten metal into fine droplets thatcool and solidify when they strike the substrate. The bonding of the sprayedmetal is primarily mechanical, with hardened metal droplets macroscopicallymeshing with the sprayed surface irregularities.

Metal arc-sprayingapplications range from coatings for corrosion control, built-up bearingsurfaces, and decorative coatings. While metal arc-sprayed coatings haveprimarily been used on metal substrates, they also adhere well to a variety ofother substrate materials. Recent industrial uses of the technology includespraying the interior of electrical equipment cases to recover some of theinherent electromagnetic shielding that is lost when using plastic instead ofmetal.

CERL has conducted aseries of experiments to test the application of various metals on commonconstruction materials used for walls in shielded rooms. These include: anexperimental zinc-on-drywall room; a zinc-on-cinder-block-sprayed laboratoryroom for processing sensitive data; a North Atlantic Treaty Organization (NATO)classroom constructed with copper-arc-sprayed fibreglass panels; a room withcopper-on-fibreglass cloth glued to poured concrete walls; and a room using zincsprayed onto fibreglasspanels. The studies have indicated that zinc andcopper are useful materials for metal arc-spraying based on cost, workability,and performance. The researchers have found that a uniform coat of zinc 12 milto 15 mil thick will satisfactorily provide an attenuation of 40 dB to 80 dB atfrequencies of 200 kHz and up. In addition, a room assembled from zinc-sprayedfibreglass panels costs about 60 per cent less than conventional bolt-togethershielded rooms.

Future studies willexperiment with applying fibreglass cloth to walls or panels before spraying.This effort will also include developing an adhesive for attaching thefibreglass cloth to the wall. The adhesive will allow the completedcomposite-sprayed shield to move when wall panel materials crack or shift.