Carlos Ranninger

MIC of stainless steels: A technical review on the influence of microstructure

Abstract Microbiologically influenced corrosion (MIC) attacks various types of material. Among these can be found stainless steels. The case histories published usually make some reference to the appearance of this type of corrosion in welded zones, which usually take the shape of pitting. This is what leads us to believe that there is a correlation between the susceptibility to this type of corrosion and to the microstructural state in which stainless steels are found. There is relatively little information available on the subject of austenitic stainless steels. It seems that, in this latter case, there is some correlation between the MIC and the sensitization state of the steel, or more exactly, with the chromium depleted zones which may exist, whether carbide precipitations are produced at the grain boundaries or in the austenite-ferrite interphase. In the case of ferritic or martensitic stainless steels, there is even less information available. There does seem to be some relation with the microstructural state; carbide stability may play a role in this. In such a case, the as-received annealed state behaves better in terms of corrosion than the quench and tempered states, especially if carried out at low temperatures. In any case, it seems that more research must be done on the subject so that the microstructural state of the materials that undergo MIC is determined in a more precise and quantative way.

Microbial induced corrosion of metallic antiquities and works of art: a critical review

Abstract Metallic antiquities and works of art are no exception to the phenomenon of microbial corrosion. Thus, all those which are buried, sunk or poorly conserved are susceptible to microbial corrosion. Although the last few decades have seen a marked development in the study of microbial corrosion of metals in industrial use, the same cannot be said for metallic antiquities and works of art. This work reviews the practical cases published, historical materials affected, and the micro-organisms involved and their mechanisms of action. Despite the great social importance of recovering these metallic cultural properties, and conserving them in a good state, there is a lack of documentation and of research groups dedicated to their study. The bringing together of researchers in works of art, microbiology and corrosion in metallic materials is shown to be necessary.

Corrosión por picaduras en depósitos de agua de acero inoxidable austenítico en trenes hotel

The water storage tanks of hotel trains suffered pitting corrosion. To identify the cause, the tanks were subjected to a detailed metallographic study and the chemical composition of the austenitic stainless steels used in their construction was determined. Both the tank water and the corrosion products were further examined by physicochemical and microbiological testing. Corrosion was shown to be related to an incompatibility between the chloride content of the water and the base and filler metals of the tanks. These findings formed the basis of recommendations aimed at the prevention and control of corrosion in such tanks. Se han detectado problemas de corrosion por picaduras en los depositos de agua de trenes hotel. Para identificar las causas se llevo a cabo un detallado estudio metalografico asi como de la composicion quimica de los aceros inoxidables austeniticos utilizados en su construccion. Tambien se realizaron estudios fisicoquimicos y microbiologicos de los productos de corrosion. Se ha encontrado que los problemas de corrosion estan relacionados con la incompatibilidad entre el contenido en cloruros del agua y los metales base y de aporte de la soldadura de los tanques. En base a estos hallazgos se proponen una serie de recomendaciones encaminadas a la prevencion y control de la corrosion de dichos depositos.