The paper presents the damage model of German Research Unit 537 which was used as a working hypothesis for the development of a user‐friendly design model. Excerpts from the laboratory experiments and numerical calculations processed in project A of the research unit are presented here. The excerpts include the quantification of self‐corrosion, geometrical effects in the macrocell corrosion, development of corroding steel surface and pit depth as well as the quantification of the resistivity of the concrete and the corrosion of steel in cracked concrete.

Reinforcement corrosion is influenced by different parameters like resistivity of concrete, setting conditions and also by concrete technology. Moreover the presence of cathodic areas and the possibility of unhampered cathodic reaction influences the reinforcement corrosion. In this paper the development of corrosion without large cathodic areas, called self-corrosion, considering different concrete parameters, is studied.

In this paper investigations into the formation of specific corrosion products during the process of chloride induced corrosion of steel in concrete are presented. The extension of corrosion products within concrete was established by means of X-ray tomography analyses. Then a detailed analysis of the nature of corrosion products has been conducted by means of Raman micro-spectroscopy and energy dispersive spectroscopy. Results emphasize two different corrosion patterns. The first one is composed of shallow cavities, where mostly magnetite and goethite were identified, traducing aerated to moderate aerated conditions in these media. The second pattern was identified as deep, needle-like pits, where chlorinated-iron-oxides phases were present associated with more or less important chloride enrichments. The presence of these particular species is indicating low redox and low pH conditions within these pits.

Within the scope of examinations at steel specimens embedded in chloride contaminated mortar for the first time X-ray tomography was used to analyse the areas, damaged by chloride induced corrosion. Damaged areas with dimensions of a few lm could be detected. The results from the X-ray tomography were verified by inspection of surfaces of the bars after removing the cover mortar.

Corrosion of steel reinforcement in concrete exposed to chloride containing environments is a serious problem in civil engineering practice. Electrochemical methods, e.g., potential mapping, provide information whether the steel reinforcement is still passive or depassivation has been initiated. By applying such techniques no information on the type of corrosion, its extent and distribution of corrosion products is available. Particular the corrosion progress is a significant problem. Especially in the case of macrocell corrosion in reinforced concrete structures, the development at the anode cannot be separated into corrosion damage resulting from macrocell corrosion or selfcorrosion. Until now also in laboratory tests it is impossible to collect such information without destroying specimens after electrochemical testing was performed. To overcome this problem it was tried to study the steel surface within the mortar specimens by X-ray tomography (CT). Within the scope of these investigations it could be shown, that X-ray tomography is suitable to make corrosion pits and their development visible which are embedded in a mortar with a cover thickness of about 35 mm. In this publication the time-dependent corrosion damage of reinforced steel is documented by X-ray tomography.