Determination of Soluble Chromium in the Overspray Generated by Various Thermal Spray Processes and Starting Materials

Thermal spraying uses a variety of starting materials and processes to produce the end coating.  The spray processes operate over a broad range of temperatures and particle velocities.   All thermal spray processes result in overspray dust and fume which contain the starting elements/compounds plus many other compounds formed during the interaction of the starting material with the spray gases and ambient environment.  Many of the wire and powder based starting materials contain chromium as part of an alloy, cermet, or oxide ceramic.  Soluble chromium contained in the overspray collected in dust collectors can render this waste stream as Hazardous.  This paper will discuss analytical results obtained from dust samples collected from numerous spray processes and starting materials.  The level of soluble chromium is correlated to the form of chromium in the starting material and to the spray process utilized.  A determination is made of the hazardous classification of the dust based upon a standard test protocol.