The vast majority of World War II military equipment has been disposed of to date. A few specimens remain in the open air as monuments or as museum exhibits in pavilions. Looking at combat vehicles that have been standing in the rain, snow and scorching sun for years and decades, a fair question creeps into the mind: why don't they rust? Is it all about regular painting or is there something else?
Of course, paint plays a role in protecting the tank from rust. However, some even suggest that armor steel is a type of stainless steel. And indeed it is! Armor steels of the Second World War belong to the class of high-alloy materials (high-alloy steel is a material with an alloy content of more than 10%). Interestingly, the recipe for armored steel in all countries has always been classified as "secret".
The percentage of ordinary iron in them does not exceed 86%. The remaining 14% is a variety of alloying additives that increase the resistance of the material to an aggressive environment. The steel was added: tungsten, chromium, manganese, copper, vanadium, molybdenum, silicon, nickel, carbon and some other chemical elements. Not all of them increase corrosion resistance. Some materials increase hardness, others increase ductility, reduce graininess, and increase the hardenability of the material. The combination of alloying elements and specific processing methods give armor steel not only high anti-corrosion properties, but also increase the resistance of the material to physical attack and reduce susceptibility to thermal impact.
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At the same time, everyone who is interested in welding understands that the weld is a potentially vulnerable place for corrosion. Its rust is fraught with the most unfortunate consequences for the entire structure. In order for the seams between stainless armor sheets not to suffer from corrosion in all countries, special welding electrodes were used - austenitic and ferritic. The main feature of such electrodes was that their wire had the highest content of alloying elements. Most often, the composition of the wire was 3% molybdenum, 19-22% nickel and 24-27% chromium. Such electrodes cost a lot of money compared to all other similar welding equipment.
In the Soviet Union, for welding tank armor, they used the latest (at that time) universal electrodes for welding structures made of high-alloy steel "UONI". They were developed at the Ukrainian Institute of Electric Welding named after E. ABOUT. Paton, founded in 1934. The same institute developed the latest method of "automatic welding" using silicon-manganese doping wire. By the way, it was largely thanks to the scientific research of local specialists that Soviet tanks not only did not rust, but were also produced much faster. Of the 400 electrodes used to weld the T-34-76 tank, only 55 were austenitic, the rest were UONI electrodes and automatic welding.
If you want to know even more interesting things, then you should read about parade tank: why the T-35 did not take root in the Red Army and how it defended Berlin.
A source: https://novate.ru/blogs/111221/61526/