Materials and Corrosion-werkstoffe Und Korrosion最新文献

The study investigates microbiologically influenced corrosion (MIC) in metallic materials in seawater, a significant problem for maritime activities and consequently threatens the structural integrity of subsea equipment. Seawater samples from the Brazilian Atlantic coast were analyzed by 16S rRNA amplicon sequencing analysis under two experimental conditions: simulation of long-term storage (MW01) and microbial corrosion with fresh samples (MW02 and MW03). The experiments showed biofilm formation and differing corrosion behaviors. Microscopic analysis indicated a more intense localized corrosion in MW02, possibly due to the high presence of Halomonas. Analysis revealed significant Bacteria and Archaea diversity, with a predominance of Thermoproteota in MW01 and Pseudomonadota in MW02 and MW03. Sulfate-reducing bacteria were detected in MW03, although in low percentages. The study highlights the complex interactions between microbial communities and corrosion mechanisms in natural seawater, providing a baseline for future research on mitigation strategies in marine environments.

Due to the risk of failure in existing prestressed concrete bridges, the assessment of the susceptibility of prestressing steel to hydrogen-induced stress corrosion cracking will become more important in the future. At present, the used normative ISO 15630-3 test gives unpersuasive and diverging results using a free corrosion approach for the needed hydrogen charging for stress corrosion cracking initiation. A newly developed test method uses the cathodic polarization to control the supply of electrons for hydrogen charging instead of an uncontrolled and variable supply of electrons by metal dissolution during free corrosion. Experimental data shows a reliable differentiation between highly susceptible known quenched and tempered wires and robust cold-drawn wires with this new test. A round robin with eight participating testing institutes demonstrated the reproducibility of results testing a cold-drawn wire batch of St 1470/1670. In contrast to previously reported experience in the literature, the new method ranks the Cr-alloyed quenched and tempered (“new-type”) wires as highly-susceptible as the “old-type” wires without Cr-alloy.

The present work investigates the suitability of impedance spectroscopy to characterize typical plastic encapsulation materials in electronic packaging. In a first approach, a commercially available epoxy mold compound (EMC) after processing to millimeters thick free-standing samples is studied. The use of free-standing samples avoids any influence of substrate/encapsulation interaction and enables the investigation of the intrinsic properties before and after harsh conditions of exposition in a Pressure Cooker Test (PCT). The change of properties of the mold material and the uptake of water is characterized with impedance spectroscopy in a 2-electrode design. Complementary material diagnostic (FTIR) confirms the results of the impedance spectroscopy. The free-standing mold failed dramatically and degraded under the conditions of the PCT due to embrittlement of the polymer and a fast water uptake. The study impressively demonstrates the (electrochemical) impedance spectroscopy as a powerful tool for qualifying and characterizing materials with extremely high impedance, such as plastic encapsulations.

This study investigates the corrosion–wear behavior of Inconel 718 produced by Selective Laser Melting (SLM) and solution treated at 980°C. Scanning electron microscopy and X-ray photoelectron spectroscopy revealed that solution treatment refined the microstructure, reduced porosity, and improved surface stability, despite a decrease in hardness from 280.32 to 245.36 Hv. In 3.5 wt% NaCl solution, corrosion current density decreased from 9.683 to 1.440 mA/cm² at +600 mV_SCE, while material loss under corrosion–wear dropped from 247 to 98 mg. Increasing the polarization potential raised corrosion rate, friction coefficient, and wear loss. For example, corrosion weight loss rose from 19 to 29 mg, and under corrosion–wear from 11 to 25 mg. Total degradation under combined conditions nearly doubled compared with corrosion alone, indicating a strong synergy between electrochemical and mechanical effects. Overall, solution treatment significantly enhances the corrosion–wear resistance of SLM Inconel 718 and supports its use in marine, aerospace, and energy sectors.

Cover:

Examples of cumulative charge of alloy 718 after potentiostatic testing for the same applied potential of 50 mV_SSC at two different temperatures of 20°C and 50°C. Optical image (a) and profilometry image shown at (b & c) for 20°C and (d & e) for 50°C.

More detailed information can be found in:

A. Reyad, T. Sapanathan, E. C. Hornus, M. Ianuzzi, Development of Environment-Time-Dependent Material Selection Maps for Alloy 718 under Crevice Conditions in Aerated Seawater, Materials and Corrosion 2025, 76, 1092.