The article discusses some inaccurate uses of pronominal forms, certain terms, syntactical and lexical mistakes in papers on welding. The article also provides the examples of mistakes found in welding papers. The use of nonpronominal forms in the denoted terms is one of the typical morphological mistakes in treating the process of welding. Another problem is the inaccurate use and wrong formation of terminology. The main lexical mistakes are semantic mistakes and calque. The article also focuses on the syntactical mistakes – the mistaken expression of purpose, the wrong use of preposition prie, redundant use of abstract nouns in treatises, also inaccurate use of infinitive with conjuction kad in dependant clauses. Causes for language mistakes and correction of errors are given.