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Joyce-Wöhrmann et. al/Thermoplastic Silver-Filled Polyurethanes for Antimicrobial Catheters shown for a hydrogen-and for an oxygen-plasma pretreated sample. Both samples show corrosion similar to filiform corrosion, but the morphology of the corrosive attack is different.The hydrogen-plasma treated sample shows a significant delamination around the defect. In the delaminated area only a thick corrosion layer can be found, the a-SIC:H-film is completely gone. This is not surprising since definitely active corrosion has occurred beneath the film and the volume of the iron oxides, which are the main corrosion products, is very large. If the adhesion of the layer to the substrate is not very high, the layer will separate from the substrate due to the high mechanical stress. [2] The corrosion filaments that are characteristic of filiform corrosion are not very pronounced in this case, but can be seen in outlines at the edges of the corroded area.The oxygen-treated sample shows a more typical filiform behavior, such as on coated aluminum. [3] Very thin filaments grow in different directions, a closer view is shown in Figure 3. In the head of the filament a different color can be seen. This is typical of filiform corrosion. This is the active head, where the corrosion reactions take place. ESCA measurements in this active head show a huge amount of chloride, which is characteristic of a filiform attack. The area behind the head is filled with corrosion products. Typically, in the case of organic coated samples the coatings stay intact, but in the case investigated the layer breaks into pieces and falls off the sample, because this inorganic film is too brittle. In contrast to the hydrogen-plasma treated sample the oxygen treated sample shows a much better adhesion of the layer to the substrate, so the area around the defect is not completely delaminated.The pretreatment of steel substrates with oxygen or hydrogen plasmas shows a significant difference in the corrosion properties. It could be shown that a-SiC:H layers are able to protect the steel substrate from atmospheric attack. In particular, they are very effective in preventing water from diffusing to the interface. At very high humidity (near 100 %) no corrosion could be observed for exposure times up to weeks. At 85 % very fast filiform corrosion occurs. The reason for this drastic change in corrosion stability with the comparatively small change in humidity is the object of current research. The adhesion of the a-SiC:H-coating to the iron oxide obtained with the oxygen plasma is better than for the surface reduced in the hydrogen plasma, as can be seen from the different degree of loss in coating around the filiform filaments. ExperimentalSamples of a common non-alloyed steel (St37) were used as substrate. The steel substrates were ground and polished to a mirror finish. The diameter of the round samples was 15 mm. Before insertion in the plasma chamber they were cleaned in 2-propanol in an ultrasonic bath and rinsed with distilled water. The deposition was ca...

The Erlanger silver catheter consists of a thermoplastic polyurethane elastomer (TPU). To achieve an antimicrobial effect, silver particles at a concentration of 0.5-1.0% by weight are incorporated into the basic material. The good mechanical properties were shown to remain present after the incorporation of the silver. The characteristic mechanical data of blends made of a soft and a hard TPU type approximated closely to a linear relationship with the ratio of the mixture. The buckling stability of catheters as a function of their cross section could be described by Euler's formula. This enables the buckling stability to be calculated when material constants and catheter geometry are known.

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The ISO 11846 Method B is one of the most frequently used corrosion tests to investigate the intergranular corrosion susceptibility of Al‐Mg‐Si(‐Cu) alloys and involves the sample immersion in an aqueous solution containing 30 g/L NaCl and 10 ml/L concentrated HCl for 24 h. Unfortunately, the standard allows for a broad range of parameter variation, for instance the temperature of the test solution and the volume‐to‐surface‐ratio of the solution related to the sample surface area, which causes insufficient reproducibility and reliability of this test method. In the present study, the influence of testing parameter variations within the scope of ISO 11846 Method B on the test results of an almost Cu‐free and a Cu‐containing variant of the 6016 aluminum alloy, both tested in the T4 condition and after a bake‐hardening treatment, was studied in detail. The results show that particularly the volume‐to‐surface‐ratio as well as the surface preparation and the solution temperature significantly influence the test results.