In January 1989, after 6 years of slow electrolysis and c.450 hours of manualwork, the Canadian Cnservation Institute completed treatment on a cast iron cannon. The 2.27 m. A long cannon was badly corroded. Radiography was carried out by Hawker-Siddeley Canada Inc., having ensured that the cannon was not loaded. The treatment given was normal for underwater corroded iron, only the object's dimensions making the project unusual. Elestrolysis carried out in a plastic lined tank using 1% w/v sodium hydroxide and 1.5 amperes current. Washing in deionized water (c. 21 months) was continued until no more chlorides could be extracted. It was dried, rust blisters removed and tannic acid used to stabilise the surface. Display in a low humidity case is recommended. Information on the maker was not found, but French origin, late 17th early 18th centuries, is thought probable.