Conduction mechanism in passive films on austenitic stainless steels in sulphate solutions

The passive state of three commercial highly alloyed austenitic stainless steels is studied by voltammetric, contact electric resistance and impedance measurements in 0.5 M sulphate solutions (pH 2-7). The three materials self-passivate and are susceptible to transpassive dissolution. The electric properties of the passive films formed are only slightly dependent on alloy composition. The impedance response can be interpreted as due to both the electronic properties of a thin semiconductor film of variable stoichiometry and the ionic defect migration through that film limiting the metal dissolution rate in the passive state. A range of kinetic, transport and structural parameters characterising the passive film and its interfaces with the underlying alloys and the electrolyte solution are determined by a quantitative comparison of the Mixed-Conduction Model to the experimental steady-state current and impedance data in a wide potential range. The relevance of the parameter values and the prospects of using the proposed approach to predict the steady-state metal dissolution rate and thus the general corrosion behaviour of stainless steels are discussed

Appendiceal Mucocele Presenting as a Right Adnexal Mass: A Case Report

A 68-year-old female presented to the Gynecologic Oncology Clinic with a right-lower quadrant abdominal mass 3 × 4 cm in diameter palpable on pelvic examination. Her routine laboratory tests were normal. Transvaginal ultrasonography revealed a cystic mass in the right adnexa 3.9 cm in diameter, which was thought to arise in the ovary. At the time of laparoscopy, a 3 × 4 cm tumor arising from the distal end of the appendix was noted. A laparoscopic appendectomy with tumor removal was performed. Histologic examination of the surgical specimen revealed a mucocele of the appendix (AM). Although rare, this tumor should be considered in the differential diagnosis of a right adnexal mass. These tumors can be identified laparoscopically and removed by minimally invasive surgery

Decomposition products of oxygen scavengers and their effect on corrosion of steam generator materials – I. Diethyl-hydroxylamine and carbohydrazide

Hydrazine used as oxygen scavenger in the secondary circuit of pressurized water reactors is hazardous to the environment and potentially carcinogenic, thus, suitable replacement chemicals for it are actively sought. In the present paper, decomposition products of two potential replacements – carbohydrazide and diethyl-hydroxylamine – are analyzed, and their effect on secondary water chemistry and corrosion of the main steam generator materials – carbon steel 22 K, stainless steel 0X18H10T and Alloy 690 – is studied by in-situ electrochemical techniques complemented by ex-situ analyses of the formed oxides by spectroscopic and microscopic methods. Quantitative interpretation of the electrochemical impedance data with the Mixed-Conduction Model allowed for the estimation of oxidation and corrosion release rates depending on scavenger formulation, alloy type and temperature. Conclusions on the extent of interaction of decomposition products with construction materials are drawn based on the experimental and calculational results.<br/

Enhanced Graphical Representation of Electrochemical Impedance Data

Bode plots, corrected for Ohmic resistance, logarithmic plots of the imaginary component of the impedance, and effective capacitance plots are shown to be useful complements to the more traditionally used complex-plane and Bode representations for electrochemical impedance data. The graphical methods are illustrated by synthetic data and by experimental data associated with corrosion in saline environments. Bode plots are shown, in particular, to be confounded by the influence of electrolyte resistance. The plots proposed here provide useful guides to model development for both reactive and blocking systems. The logarithmic plots of the imaginary component of the impedance and effective capacitance plots are useful for all impedance data, and the correction for Ohmic resistance in Bode plots is useful when the solution resistance is not negligible

Primary amyloidosis with initial gastrointestinal manifestation. A case report

Introduction. Amyloidosis is a rare disease associated with extracellular accumulation of abnormal protein – amyloid in various organs and systems. This disease can be either acquired or hereditary, systemic or localized. At its core, it represents a grown, tumor-like neoplastic clone of the plasma cells in the bone marrow. Gastrointestinal amyloidosis is manifested by symptoms, such as diarrhea, steatorrhea, constipation, and very rarely – hemorrhages and perforations of the colon. Case presentation. We present a case of primary intestinal amyloidosis with recurrent hematochezia and abdominal pain in a 61-year-old woman. Colonoscopy revealed polyposis of the whole colon and a total colectomy was performed, followed by morphological and paraclinical examinations. Histologically, amyloid deposition, positive for Congo red, was found in the walls of the submucosal blood vessels and in the smooth muscle cells of the muscular layers. The laboratory tests indicated anemia, high erythrocyte sedimentation rate, and Bence-Jones proteins in urine. Conclusions. Our case is a demonstration of primary amyloidosis with intestinal localization that should be taken into consideration in the presence of recurrent hematochezia

Passive and transpassive behaviour of Alloy 31 in a heavy brine LiBr solution

The passive and transpassive behaviour of Alloy 31, a highly alloyed austenitic stainless steel (UNS N08031), has been investigated in a LiBr heavy brine solution (400 g/l) at 25 °C using potentiostatic polarisation combined with electrochemical impedance spectroscopy and Mott-Schottky analysis. The passive film formed on Alloy 31 has been found to be p-type and/or n-type in electronic character, depending on the film formation potential. The thickness of the film formed at potentials within the passive region increases linearly with applied potential. The film formed at transpassive potentials is thinner and more conductive than the film formed within the passive region. These observations are consistent with the predictions of the Point Defect Model for passive and transpassive films on metals and alloys