Zimmerit was a non-magnetic coating produced for German armored fighting vehicles during World War II for the purpose of combating magnetically attached anti-tank mines. It was developed by the German company Chemische Werke Zimmer AG.
The coating was a barrier that prevented direct contact of magnetic mines with metal surfaces of vehicles. It was normally ridged to increase overall thickness. The magnetostatic field decreases very rapidly, with the cube of distance; the non-magnetic coating holds the magnet of the mine too far from the steel of the vehicle for it to adhere.
Zimmerit was applied to some tanks and casemate-style closed-top self-propelled guns and tank destroyers produced from December 1943 to 9 September 1944. It was only rarely applied to open-top AFVs. The rough appearance of the coating gave a distinct appearance, for one type a “shingle-like” look to the vehicles it coated.
Application of Zimmerit was usually done at the factory. The many variations seen in application designs, from the regular ridge-shaped pattern, to a less common waffle-shaped pattern, are mostly related to the factory producing each type of AFV. For example, the waffle pattern was seen almost exclusively on Sturmgeschütz III assault guns. In general, vehicles already in service were not coated with Zimmerit.
Zimmerit was discontinued from factory application on 9 September 1944 and from field application on 7 October 1944. This was due to concerns that projectile impacts could ignite it. These proved false, but the order was never rescinded. Applying and drying the paste added days to the production of each vehicle, which was unacceptable as there was a shortage of tanks.
Following the war, the British carried out trials of a similar material on Churchill and Cromwell tanks and some trials were conducted in Canada with a similar material applied to self-propelled guns but it was not implemented. No similar material was used on post-war tanks as the widespread use of man-portable HEAT rockets such as the Bazooka made magnetic mines obsolete.