Volume 3, Issue 5 (May 2006)
Surface Ignition of Aluminum in Oxygen
Published reports of burning aluminum in oxygen using ASTM G 124-type testing demonstrated that aluminum alloys are difficult to ignite but once ignited are extremely flammable in terms of regression rate and energy release. The ignition resistance of aluminum is associated with its tenacious and protective oxide, which allows aluminum to safely contain high-pressure oxygen in certain applications. The ignitability of aluminum varies between alloys and surface treatments so a test method was developed to evaluate the ignitability of various aluminum surfaces. The test method uses a promoted ignition chamber consistent with ASTM G 124 testing; however, the test sample is configured in the shape of a coupon. Instead of promoting the sample with an electrically heated wire, a controlled electrical arc is generated by drawing an electrode away from the center of the coupon while passing current through the sample. The level of energy applied to the surface of the coupon is semi-quantifiable and kept constant between tests. Based on this semi-quantifiable amount of energy, an ignition pressure is established and the influence of alloy composition and surface treatments on aluminum is evaluated.