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Organisationseinheit der BAM
The salinization and contamination of metal surfaces by chloride-containing aerosols is of great importance with regard to corrosion phenomena of damaged coated metal surfaces and stainless steels in the maritime sector and in offshore applications. Detailed questions have to be answered to clarify whether and to what extent salinization of the surface has an influence on the adhesion and durability of coatings in repairing applications and on pitting occurrence on stainless steels under atmospheric conditions. The questions arise which degree of salinization is reached after which period of time and how a defined and reproducible salinization can be simulated in the laboratory for further systematic investigations. The article is dedicated to these questions. Results of a field trial on the Island of Heligoland are presented and a simple procedure for a defined loading of metal surfaces with chlorides at a laboratory scale using a design of experiments (DoE) approach is introduced.
The corrosion resistance of aluminium surfaces is closely linked to the surfacecstate after a grinding process. For years, iron‐containing abrasive materials were suspected to lead to increased corrosion susceptibility after processing of aluminium surfaces. To prove a possible correlation between the iron content of an abrasive and the corrosion behaviour of aluminium components, scientific investigations and experimentally practical corrosion tests are necessary.
For the current investigation, specimens of a technical Al‐Si alloy from the same batch were used. The test specimens were mechanically ground with various resin‐bonded model abrasives containing different iron contents. The performed corrosion tests did not reveal a negative influence of the different iron‐containing abrasives on the corrosion behaviour of the Al–Si alloy.
However, the most sensitive measuring method (electrochemical noise)
showed differences in the surface activity depending on the type of abrasive.
Investigations of corrosion on small cathodes in reinforced concrete - observations and suggestions
(2009)
Corrosion of steel reinforcement in concrete exposed to chloride containing environments is a serious
problem in civil engineering practice. The standards and guidelines contain only minimum
requirements regarding concrete quality and concrete cover. In very critical cases, for example the
ingress of chlorides, the application of different coatings is currently the only possibility to protect the
reinforced concrete structures. In this case the modelling of reinforcement corrosion would be more
practical. One sub-project of a DFG-research project (FOR 537) is currently performed at the Federal
Institute for Materials Research and Testing (BAM). Aim of the sub-project is the description of
corrosion propagation and the characterization of the corrosion on specimens with small cathodes by
electrochemical parameters. The electrochemical parameters are determined by suitable
electrochemical measurements, considering concrete parameters as well as different environmental
conditions.
Electrochemical half-cell potential measurements for the detection of reinforcement corrosion
(2014)
This specification describes the application of electrochemical half‐cell potential measurements (frequently also called potential mapping) for the detection of reinforcement corrosion in reinforced concrete structures. Areas of corroding reinforcement steel can be located in a nondestructive manner by means of this procedure. Half‐cell potential measurements are used in order to detect chloride‐induced corrosion. However, it is not recommended in order to assess the risk of carbonation‐induced corrosion. For this purpose the determination of the carbonation depth and the concrete cover appear to be more appropriate.
The content of this specification exclusively refers to the application of mobile, local variable reference electrodes, which are only placed on the concrete surface while measuring. The technique distinguishes itself thereby from the range of corrosion monitoring systems with stationary installed reference electrodes and sensor systems, respectively, whereby it is possible to continuously track measurements within the area of the installed electrodes. However, these methods are not dealt with in this specification.
Dieses Merkblatt beschreibt die Anwendung elektrochemischer Potentialmessungen (häufig auch als Potentialfeldmessung bezeichnet) zur Detektion von Bewehrungsstahlkorrosion an Stahlbetonbauwerken. Mit Hilfe dieses Verfahrens können Bereiche korrodierender Bewehrung zerstörungsfrei lokalisiert werden. In der Regel kommt diese Messmethode bei der Detektion chloridinduzierter Korrosion zum Einsatz. In Abgrenzung hierzu sollte die Abschätzung der Gefahr einer karbonatisierungsinduzierten Korrosion durch Bestimmung der Karbonatisierungstiefe und der Betondeckung erfolgen.
Im Zusammenhang mit Planungs- und Entwicklungsaufgaben, den Forderungen in Normen und Regelwerken, in betrieblichen Arbeitsanweisungen, den Vorgaben für Zulieferteile oder bei der Auseinandersetzung mit Schadensfällen stellen sich häufig Fragen zum Korrosionsschutz sowie zu entsprechenden Prüf- und Untersuchungsverfahren. Die daraus gewonnenen Ergebnisse sollen z. B. eine Eignung von Werkstoffen oder Schutzsystemen unter spezifischen Einsatzbedingungen, die Dauerhaftigkeit des Schutzes, den Nachweis einer gleichbleibenden Qualität, die Vergleichbarkeit bekannter mit neuen Korrosionsschutzkonzepten oder den Wirkungsnachweis für gezielte Systemeingriffe belegen. Schnell wird deutlich, dass sich aus dem Blickwinkel verschiedener Branchen ganz unterschiedliche Anforderungsprofile ergeben, die ihren Niederschlag dann in unterschiedlichen Strategien der Prüf- und Untersuchungsverfahren finden.
In addition to constructional requirements in civil engineering stainless steels often have to fulfil high visual demands. Unexpected impairments of the visual appearance of stainless steels under low corrosive conditions are a widespread problem today. Frequently it is supposed that this is caused by changes in the alloy composition, worse environmental conditions or improper handling. Within a research project the systematic investigation of several cases of damaged stainless steel bars has shown that the reasons are based on well-known material defects like chemical inhomogeneities (e.g. precipitations or local carburization) or geometrical defects (e.g. undercuts, rolling defects or shell formation). Thus, the failures could be clearly identified as production failures of the respective semi-finished products.