Martensitic high strength steel type of 22MnB5 is increasingly used in transport industries for safety components. Al-Si based coating layer is applied to the steel surface to prevent oxidation during hot stamping process. The main objective of performed analyses is to study the differences in formation of the surface AlSi layer related to weldability of martensitic steels. The structure of sub-layers and changes of their chemical composition were studied as a result of different thermal conditions during heat treatment. Formation of silicon-enriched zones in connection with overheating during austenitization is discussed. Tendency for creation of brittle inter-metallic phases based on Al-Fe was revealed.