Manfred Gugau

Zum Verhalten rost- und säurebeständiger Stähle unter Komplexbeanspruchung. Teil 1 Passivität und Lochkorrosionsbeständigkeit

Iron-Chromium-Nickel alloys are of special interest for many applications because of their excellent resistance to corrosion. The nature and composition, of passive films formed on stainless steels depend on the prevailing conditions, viz. steel-composition, passivation potential, aging, pH, electrolyt composition and temperature. Passive films may be damaged by local breakdown. At least two mechanisms are possible for this localisation: mechanical breakdown by slip steps and electrochemical breakdown (for e.g. by the effects of chloride ions). Because of this, steels suffer a degradation of their fatique properties when exposed to an aqueous environment. Passivation of austenitic, ferritic-austenitic and martensitic stainless steels has been studied in different solutions using electrochemical techniques. The results clarified that for two of the investigated alloys the prediction of fracture initiation based on pitting corrosion in chlorid containing solutions is possible.

Korrosions- und Kavitationsverhalten von Leichtmetallen in Kühlkreisläufen von Verbrennungskraftmaschinen

Verbrennungsmotoren werden zum Abtransport von Verlustwarme und zur Vermeidung von Uberhitzung in der Regel flussigkeitsgekuhlt. Zunachst wurde hierfur reines Wasser ohne weitere Zusatze verwendet. Mit dem Einsatz schnellaufender Schiffsdieselmotoren traten jedoch schon nach zum Teil nur 20 000 Betriebsstunden kuhlwasserseitige Schaden an Zylinderlaufbuchsen auf. Vor gut vierzig Jahren beauftragte die im Jahre 1956 gegrundete Forschungsvereinigung Verbrennungskraftmaschinen e. V. (FVV), Frankfurt am Main, das Institut fur Werkstoffkunde der TU Darmstadt mit der Aufgabe, derartige Schaden zu untersuchen, wenn moglich zu klaren und Abhilfemasnahmen zu erarbeiten. Seit dieser Zeit wird die Problematik der Korrosion in Kuhlsystemen behandelt. Corrosion and cavitation behaviour of light metals in cooling systems of combustion engines Combustion engines are liquid-cooled, in general, in order to transport away dissipated heat and to avoid overheating. Initially, pure water without any further additives was employed for this purpose. With the introduction of high-speed marine diesel engines, however, sometimes after only 20 000 operating hours there occurred damage at the cylinder liners that had been exposed to the cooling water. More than forty years ago, the Research Association Internal Combustion Engines, Registered Association (FVV), Frankfurt am Main, which was founded in the year 1956, commissioned the Institute of Materials Science of the Darmstadt University of Technology to investigate and, if possible, clarify damage of this type and to elaborate corrective action. Since that time, the problem of corrosion in cooling systems has been worked on.