Determining the sequence of elimination of impurity ions from the surface of historical cold iron weapons

Abstract

Confirming the authenticity of historical cold weapons and determining their age is an urgent problem in practical examination. One of the promising directions for its solution is the experimental study of the process of elimination of impurity ions from iron, which occurs throughout the long history of life. This paper describes a model that explains the sequence of elimination of impurity ions from near-surface parts of the metal. Deformation indicators of the crystal lattice of iron were calculated and sorted in order of decreasing ionic radius of the impurity chemical element. A diagram of the deformation effect of impurity chemical elements on the volume-centered crystal lattice of iron was constructed. Ions that are larger in diameter are more actively eliminated from the surface layers of the metal, while ions that are smaller are removed to a lesser extent. With the help of the authors’ methodology, a study of the chemical composition of the surface of collection samples of iron cold weapons of the 20th, 19th, and 18th centuries was carried out. It has been established that a metal alloy made in the recent past ‒ up to 100 years ‒ is characterized by a very active release of impurity chemical elements on the surface when it is heated. Iron weapons made up to 200 years ago have a significantly lower ability to release chemical impurities because most of the latter have already been eliminated. At the same time, samples of cold weapons of this age already have microdefects in the form of cleavage cracks and caverns, so their surface contains a significant number of compounds of eliminated chemical elements that have accumulated during the long history of their use. Older cold weapons, made 300 years ago or earlier, have impurity ions that are smaller than ferric ions, particularly silicon. The results of the research are important for the identification and authentication of historical iron cold weapons