In spite of the recommendation to remove the coating in the welding area (mostly corrosion protection) prior to the welding of coated metal sheets, as dangerous emissions must be expected during the thermal decomposition of a coating, the coating residues at least are in practice frequently welded over. Goal: qualitative determining and assessment of the hazardous substances resulting from the heat decomposition of the covering and its danger potential under worst-case conditions.
Laboratory test; active gas metal arc build-up welding on St37 sheets with 5 different coatings typically used in ship building - not removed in the welding area - (epoxy resin, urethane modified alkyd resin, epoxy tar, alkyd resin, vinyl/epoxy resin (containing tar)); recording and characterisation of the resulting hazardous substances, in particular total dust, aromatic hydrocarbons BTX, polycyclic aromatic hydrocarbons(PAH), aldehyde, phenol/cresol, arylate
The emission rates of the decomposition products amount to 8-24 mg/s (during welding of completely coated metal sheets: worst case); a various number of hazardous substances including the aromatic and cyclic hydrocarbon groups as well as terpene were detected, amongst others formaldehyde, acetaldehyde, acryaldehyde, naphthalene, benzene and delta-4-caren. The qualitative analysis is insufficient for quantitative determination of the risk potential. This should be carried out in a follow-up project.
Mitteilungsblatt "Gesund und Sicher" der Norddeutschen Metall-Berufsgenossenschaft 7/98, S. 208-210
Schweißen und Schneiden Heft 11, Seite 736-738, DVS-Verlag, 11/1998
metal workingType of hazard:
Gefährdungsbeurteilung, Chemische Arbeitsstoffe, Krebserregende StoffeDescription, key words:
High levels of hazardous substances through thermal decomposition of coated metal sheets in welding