Lisbeth Rischel Hilbert

Influence of surface roughness of stainless steel on microbial adhesion and corrosion resistance

Abstract The aim of this study was to evaluate whether hygienic characteristics of stainless steel used in the food industry could be improved by smoothing surface roughness (Ra) from Ra 0.9– 0.01 μm . The adherence of Pseudomonas sp., Listeria monocytogenes and Candida lipolytica, to stainless steel was not affected by surface roughness ranging from grit 4000 polished stainless steel (Ra ( Ra 0.9) . Neither adhesion of Ps. aeruginosa nor its removal by an alkaline commercial cleaner in a flow system was affected by surface roughness. Pitting corrosion resistance was evaluated in a commercial disinfectant and in 1 M NaCl. Electropolished and grit 4000-polished steel proved more corrosion resistant as opposed to grit 80- and 120- polished surfaces. In conclusion, the surface finish did not influence bacterial attachment, colonziation or removal, but is an important parameter for the corrosion resistance of the surface.

Siderite as a Corrosion Product on Archaeological Iron from a Waterlogged Environment

Abstract This paper discusses the occurrence of siderite (FeCO3) on iron artifacts excavated from the waterlogged peat and gyttja sediment of the Danish Iron Age site Nydam Mose. Siderite was identified by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy-dispersive spectrometry (SEMEDS), which showed only minor contents of other minerals in the corrosion scales. The implications of the formation of siderite as a corrosion product are discussed in terms of its possible passivating properties and thermodynamic stability in situ. A Pourbaix diagram adjusted to the actual conditions in Nydam is presented and discussed. Different mechanisms for the formation of siderite in this environment are proposed, based on the results of environmental monitoring in the area.

Silver-palladium surfaces inhibit biofilm formation.

ABSTRACT Undesired biofilm formation is a major concern in many areas. In the present study, we investigated biofilm-inhibiting properties of a silver-palladium surface that kills bacteria by generating microelectric fields and electrochemical redox processes. For evaluation of the biofilm inhibition efficacy and study of the biofilm inhibition mechanism, the silver-sensitive Escherichia coli J53 and the silver-resistant E. coli J53[pMG101] strains were used as model organisms, and batch and flow chamber setups were used as model systems. In the case of the silver-sensitive strain, the silver-palladium surfaces killed the bacteria and prevented biofilm formation under conditions of low or high bacterial load. In the case of the silver-resistant strain, the silver-palladium surfaces killed surface-associated bacteria and prevented biofilm formation under conditions of low bacterial load, whereas under conditions of high bacterial load, biofilm formation occurred upon a layer of surface-associated dead bacteria.

Real time corrosion monitoring in atmosphere using automated battery driven corrosion loggers

Abstract A logger enabling continuous measurement of corrosion rate of selected metals in indoor and outdoor atmospheres has been developed. Principle of the measurement method is based on the increasing electrical resistance of a measuring element made of the material concerned as its cross-sectional area diminishes due to corrosion. Zinc, iron, copper and nickel sensors at several thicknesses are available. Sensitivity of the corrosion measurement varies from 1 to 10 nm depending on the type and thickness of the sensor. Changes in the air corrosivity can be thus detected within hours or even tens of minutes. The logger lifetime in medium corrosive environments is designed to be 2 years with full autonomy. Data on the sensor corrosion rate are available any time through GPRS connection or by a non-contact inductive reading without the need of retracting the logger from the exposure site.

Comparison of adhesion of the food spoilage bacterium Shewanella putrefaciens to stainless steel and silver surfaces

Aims: To compare the number of attached Shewanella putrefaciens on stainless steel with different silver surfaces, thus evaluating whether silver surfaces could contribute to a higher hygienic status in the food industry.

16 – Long-term corrosion of iron at the waterlogged site of Nydam in Denmark: studies of environment, archaeological artefacts, and modern analogues

Publisher Summary This chapter focuses on long-term corrosion of iron at the waterlogged site of Nydam in Denmark. It compares the behavior of archaeological and modern iron in a waterlogged soil and reviews all the studies on iron corrosion. It examines the feasibility of preserving the remaining archaeological artefacts in situ at Nydam and compares the corrosion pattern observed for modern and archaeological iron. The work at Nydam has focused solely on the preservation of the archaeological artefacts. However, it should be possible to use the same data, samples, and artefacts to discuss the long-term corrosion of modern iron, for instance, in relation to the storage of radioactive waste. Sacrificial sites such as Nydam may be especially suited for that purpose as it is possible to have at least some information about the burial conditions of the artefacts from the Iron Age until today.

Nickel-containing coins : a health risk for nickel-sensitive individuals?

recent study analysing the effects of narrowband ultraviolet B on patients with nonsegmental vitiligo, it was reported that the patients showed marked response in 76Æ3% of facial lesions, 41Æ9% of truncal lesions and 37Æ6% of limb lesions. None of the patients achieved marked response in acral acreas. This result is remarkable and has important implications. The repigmentation process in vitiligo after phototherapy involves reactivation of MCs located in the hair outer root sheath or from the contiguous pigmented skin from which the MCs migrate into the depigmented skin. Although the number of hair follicle units per unit area and the amount of epidermal MCs in the acral area may provide a partial explanation for this phenomenon, it is likely that other factors, such as certain dermal components of acral parts, may impede proper MC migration. This hypothesis, if proven correct, would explain the scarcity of reports on acral pigmented EP and lack of therapeutic response in acral vitiligo. Therefore, further investigations on the differences in dermal components, particularly the distribution of different extracellular matrix components that have been shown to be important in MC migration, among various anatomical regions, are indicated to elucidate further the pathomechanisms involved in these two seemingly different yet closely associated clinical observations.

Reliability of Electrochemical Techniques for Determining Corrosion Rates on Carbon Steel in Sulfide Media

Abstract Effects of film formation on carbon steel in hydrogen sulfide (H2S) media may corrupt corrosion rate monitoring by electrochemical techniques. Electrochemical data from H2S solutions, biol...

14th Nordic Corrosion Congress

Abstract The 14th Nordic Corrosion (NKM) Congress took place in Copenhagen between 13 and 15 May 2007. NKM congresses date back to 1954, and the most recent, NKM13, was a successful international event in Iceland in 2004. The main organisers of NKM14 were Per Møller and Lisbeth Hilbert from Danish Technical University (DTU).

Study of electroplated silver–palladium biofouling inhibiting coating

Abstract Biofouling can cause many undesirable effects in industrial and medical settings. In this study, a new biofouling inhibiting Ag–Pd surface was designed to form an inhibiting effect by itself. This design was based on silver combined with nobler palladium, both with catalytic properties. Owing to the potential difference between silver and palladium while contacting with an electrolyte, the surface can form numerous discrete anodic and cathodic areas, so that an inhibiting reaction can occur. In this paper, a series of electrochemical and biological investigations were conducted to study the properties and biofouling inhibiting mechanism of these surfaces. In this study, the evidence is presented that the inhibiting effect can be caused by the electrochemical interactions and/or electric field between Pd and Ag/AgCl combined with an organic environment.