Latent Incompatibility of Stainless Steel with Lead Azide Primer – A Case Study

While designed to be lethal, army ordinance ammunition must also be safe to store, transport and deploy, maintaining chemical and physical stability for many years.

The chemical compatibility between lead azide primary explosive and its X8CrNiS18-9 1.4305 grade stainless steel was investigated under accelerated weathering conditions that eventually introduced an ion conducting environment.

The scope of the research is to chart possible, practical, chemical causes leading to the migration of copper from the stainless steel metal lattice, where the concentration is a mere 0.4%, into solution with the lead azide forming the extremely sensitive and unpredictable copper azide.

The resulting incompatibility is very dangerous, yet, not evident - thus best described as "latent incompatibility."

In the case study presented a lead azide primer was subjugated to weathering while in intimate contact and indirect contact to X8CrNiS18-9 1.4305 stainless steel. The resulting products of the reaction were carefully characterized to detect suspected copper azide by means of advanced spectroscopic apparatuses (ICP, XRD), SEM and light microscopy.

The work shows concisely that X8CrNiS18-9 1.4305 stainless steel lends itself to migration of copper from the metal lattice into solution with the azide primer, where due to strange affinity, will replace lead ions to form copper azide (or more precisely cupric azide).