The ignition of inflammable gases by sparks from aluminium paint and rusty steel

Abstract

AbstractIn certain circumstances steel coated with aluminium paint can emit sparks when struck with a metal striker, and such sparks may ignite mixtures of inflammable gases or vapours in air. The sparks are due to the thermite reaction between iron oxide and aluminium, and therefore are produced only in the presence of iron oxide. The extent of this hazard depends on the nature of the paint; it is increased if the painted steel is subjected to heat.This work was therefore carried out to determine the effect of the nature of the paint, and the temperature to which the paint might be subjected in use on the tendency to produce incendive sparks (i.e. those liable to ignite inflammable gases or vapours).The investigation was divided into two sections, the first dealing with certain preliminary studies on the conditions necessary for the production of sparks and the reaction involved in spark formation, and the second consisting of a survey of the possible hazard with a representative series of commercial paints.No exact correlation between paint composition and liability to emit sparks was obtained, but none of the commercial oil‐bound paints tested gave sparks unless the specimen had been heated to at least 150°.The paper includes a note by the Senior Chemical Inspector of Factories, outlining the practical application of the results.