Throw Back Thursday – UNPX Aluminum Covered Hopper Cars

by Keith MacCauley 

Sodium chlorate is a chemical salt primarily used in the bleaching of pulp as part of paper making. Given its corrosive nature, transport of sodium chlorate has special requirements, mostly related to compatible materials. In addition to tank cars, Procor also designed and manufactured specialty freight cars. A first attempt at transporting sodium chlorate in smaller 2,900 cu. ft. steel covered hopper cars proved unsuccessful. Despite having protected coated (painted) interiors, over time, corrosion progressed to the point whereby the roofs were unsafe to walk on. Changing the material of construction to aluminum solved the corrosion problem. Collaborating with Alcan and Canadian National Railway’s freight car engineering group a design based on the lightweight aluminum CNWX grain car was created. Further to an initial build of twenty cars (UNPX 120500 – 120519) Procor would go on to assemble fleet of some 1,300 aluminum bodied covered hopper cars. It is said that imitation is the sincerest form of flattery. Two other well-known builders would produce clones of the Procor designed sodium chlorate hauler; albeit with varying degrees of success.