Flame cleaning with acetylene is used wherever clean sheet metal surfaces are required for further processing. Rust, mill scale, and other scale are efficiently removed by low-cost flame cleaning. Flame cleaned surfaces ensure excellent adhesion of paint and coatings. Thereby, corrosion resistance is also improved. Flame cleaning procedures are also used for thermal treatment of concrete and natural stone surfaces. In particular for cleaning and preparatory pretreatment of concrete carriageway surfaces. Also old paint and coatings, oil contamination, and abraded rubber can be removed in an environmentally friendly way. The concrete thus exposed gives optimal adhesion for synthetic resin coatings.