Black powders coming from the interactions of pipe and other metals with the environment in gas transmission line can cause severe problems in the industry. In this work the composition of the collected black powder from up stream of the filtering system analyzed using XRF and XRD techniques. Erosion test is carried on the samples of impeller alloy in the black powder alcoholic slurry in a laboratory set up. It is shown that the main constituent of the black powder is magnetite. The rotation speed and presence of humidity can enhance the erosion/corrosion with the consequence of more black powder production.