Pitting Of Stainless Steel Research Articles

Care and Handling of Basic Surgical Instruments

A well-made, properly cared-for instrument can be expected to last 10 years. The most important considerations in extending the life of an instrument are appropriate use, careful handling, and proper cleaning and sterilization. Every instrument is designed for a specific purpose. Using it for an unintended purpose is a sure method of damaging an instrument. Examples of misuse include securing surgical drapes or opening a medicine vial with an instrument designed to grasp tissue. The proper cleaning of instruments during and after surgery can help to prevent stiff joints, malfunctions, and deterioration of the instruments’ material, including stainless steel. During surgery, instruments contaminated by blood or tissue should be properly wiped and rinsed in the sterile distilled water in the sterile field. Thorough rinsing is important to ensure removal of blood and other contaminants from hinges, joints, and crevices. Blood and foreign matter that are not removed or are allowed to dry and harden may become trapped in jaw serrations, between scissor blades, or in box locks, making final cleaning more difficult and the sterilization or disinfection process ineffective. It can cause instruments to become stiff and eventually break. Channels, or lumens, within instruments such as suction tips should be irrigated periodically to prevent blood from drying and adhering to the inside of the lumen. Neglecting this action can cause blood and other debris to remain in lumens throughout the postoperative cleaning, decontamination, and sterilization processes. A syringe should be present in the sterile field for the purpose of flushing lumens with water throughout the procedure. Flushing the lumen should be done below the surface of the water to prevent the aerosolization of debris. Instruments should be rinsed in distilled water. Saline should not be used for this purpose. Prolonged exposure to saline can result in corrosion and can eventually lead to the pitting of stainless steel. Pitting can permit entrapment of debris, interfere with sterilization, and result in the destruction of an instrument. Instruments should be handled carefully and gently, either individually or in small lots, to avoid possible damage caused by their becoming tangled, dented, and misaligned. During and after surgery they should be placed, not tossed, into the basin. Heavy instruments should be on the bottom, with the lighter, more delicate and fragile ones on top. Rigid endoscopes and fiberoptic cables should also be placed on top or separated. Fiberoptic cables should be loosely coiled, never wound tightly. When the procedure is complete, instruments that can be immersed are disassembled and all box locks are opened. Care should be taken to ensure that they are not tangled or piled high. Instruments should be returned to their respective containers or baskets to prevent sets from becoming incomplete, and they should be covered for transport to the decontamination area. All disposable blades and sharps should be removed and placed in a designated sharps container. Delicate instruments, endoscopes, and other specialty instruments may have to be separated and transported to the decontamination area in containers specifically designed to prevent damage to these devices. Instruments with cutting edges, pointed tips, or other sharp components should be placed in such a manner that sharp edges are protected and personnel responsible for cleaning and decontamination are not injured when reaching into the container.

Effect of Nickel on Metastable Pitting of Stainless Steels: Computer Simulations Study

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Pitting transients analysis of stainless steels at the open circuit potential

Metastable pitting of stainless steels in chloride containing oxidising electrolytes is investigated at rest potential using a new experimental technique allowing to record simultaneously the potential and corrosion current variations. Different industrial surface conditions (BA and 2B) are tested for both ferritic (FeCr type) and austenitic (FeCrNi type) stainless steels. It was shown that the number of pitting events decreases with the exposure time and that BA condition provides better resistance to pitting than 2B. As far as pitting mechanisms are concerned, the potential recovery after pitting does not reflect the pit repassivation but rather refers to the discharge of the surface capacity. Analysing the pitting transients provides quantitative information on the cathodic reaction through the passive film (transfer resistance and surface capacitance). Differences in pitting transient shapes are discussed as well.

Computer simulation of pitting potential measurements

A deterministic model for the growth of single pits in stainless steel has been combined with a purely stochastic model of pit nucleation. Monte-Carlo simulations have been used to compare the predictions of this model with potentiodynamic experimental measurements of the pitting potential. The quantitative agreement between model and experiment is reasonable for both 304 and 316 stainless steel, and the effects of varying surface roughness, solution chloride concentration and potential sweep rate have been considered.

Kinetics of Galvanostatic Chloride Pitting of Stainless Steels in Chloride Solutions

To check the theory, the corrosion of steels 12X18H10T and 10X17H13M2T is studied during galvanostatic polarization at different \(C_{Cl^ - }\), current densities, and temperatures. The morphology and size distribution of pits are discussed. In E vs. logτ curves are shown to demonstrate a single linear segment for steel 12X18H10T and two linear segments for 10X17H13M2T (as for pure Fe, according to the literature data [12]), namely, the initial segment with a steep slope and the later one with more gentle slope. The single slope ¦− ∂E/∂ log τ of steel 12X18H10T and the later (gentle) slope, which is observed for both steel 10X17H13M2T and Fe, correspond to those predicted in [3, 4, 7], while the earlier steep slope corresponds to crevice-type pitting.

The composition of the boundary region of MnS inclusions in stainless steel and its relevance in triggering pitting corrosion

Recently, controversy has arisen on the presence of a Cr-depleted zone around MnS inclusions in stainless steels and the relevance of such zones to pit initiation events. In the present work, we use a scanning Auger microscope (SAM) combined with simple pitting immersion tests to elucidate this question in more detail. The SAM analysis of 27 inclusions of a high S-containing DIN 1.4305 stainless steel indicated no Cr-depletion at the inclusion/matrix-interface with a lateral resolution of ±20 nm. A scanning electron microscope (SEM) characterization of the sample surface after an exposure to 10% FeCl 3 solution shows that pitting attack in all cases initiates at inclusion sites. Different pit initiation morphologies were observed (inside the inclusion, around the inclusion, mixed attack morphology). However, even the attack morphology “around an inclusion” cannot be ascribed to Cr depletion at the inclusion. Although in special cases (special composition or heat treatment history of the steel) a Cr-depleted may be induced at the matrix/inclusion-interface, the present work shows that this approach does not generally hold and therefore the presence of such a depletion zone cannot be the general explanation for pitting of stainless steels in the vicinity of inclusions.

Effect of Iron-Oxidizing Bacteria on Pitting of Stainless Steel

Abstract Microbiologically influenced corrosion (MIC) of stainless steel (SS) can be caused by the action of metal-oxidizing bacteria (MOB) in natural, relatively low-chloride waters. This type of ...

Microbiologically influenced corrosion of stainless steels – What is required for pitting?

AbstractPitting of stainless steels in environments normally regarded as completely harmless is often attributed to microbial activity. In this paper, attention is drawn on one hand to the basic requirements for pitting of stainless steels to be possible, and on the other hand to various ways how microbial activity could contribute to a fulfilment of these requirements. For pit growth to be possible, three basic requirements must be fulfilled: 1) the environment must contain anions that can form an aggressive solution into the pit, 2) there must be a potential difference between the interior of the pit and the open surface outside the pit, 3) the temperature must exceed a critical value. The main factors that normally influence the possibility of pitting are the chloride content and the oxidising power of the environment, presence of anions other than chloride, temperature, possible presence of deposits on the steel surface, and the composition of the steel. Anions other than chloride in the bulk solution, including sulphate, usually have an inhibiting effect. Thiosulphate, however, is known to promote pitting under certain conditions. The possible ways of microbial activity to enhance pitting could include deposit formation leading to crevice type of attack, local modification of the composition of the environment to a more concentrated one, raising the electrode potential of the steel surface (“ennoblement”), or formation of reaction products that permit active dissolution inside a pit at lower potentials. Special attention is drawn to the possible action of thiosulphate by enhancing the anodic reaction at low potentials of the dissolving surface inside the pits.

The aspect ratio of surface grooves and metastable pitting of stainless steel

The metastable pitting behavior of 316L stainless steel with different surface roughness in 0.01 M NaCl solution was studied using potentiostatic and potentiodynamic polarization methods and statistical treatments. As surface roughness decreased, the nucleation rate of metastable pits decreased. The peak current of metastable pits also decreased, but the average growth rate of metastable pits showed a slight increase. The aspect ratio of surface groove, w/ d, was suggested to characterize the openness of surface grooves, in which w is the width of the groove at the opening and d the depth of the groove. Bigger w/ d value indicates more smooth surface, and it is more difficult for micro-pit to nucleate. Under certain conditions of solution and potential, there is a critical w/ d value. Metastable pits may nucleate only on those surfaces whose w/ d values are less than the critical value. As the aspect ratio w/ d increases, the nucleation rate of metastable pits decreases linearly, and both metastable pitting potential E m and pitting potential E p move in the positive direction.

Computer Simulation of Single Pit Propagation in Stainless Steel under Potentiostatic Control

A model is proposed for the propagation of corrosion pits in stainless steel under potentiostatic conditions. The model is based on the requirement of a near-saturated local chemistry in the pit and uses an equation previously formulated for the anodic dissolution kinetics in this environment. Salt film precipitation, electrolytic migration, and transport outside the pit are each considered explicitly. Numerical simulations of pit growth have reproduced the experimentally observed characteristics of pitting, including development of a pit cover, spontaneous repassivation of metastable pits, increased stability at higher applied potentials, and a tendency for pits to become dish-shaped rather than hemispherical. © 2001 The Electrochemical Society. All rights reserved.

In situ observation of pitting of stainless steel by XAFS.

An in situ observation technique by XAFS (X-ray Absorption Fine Structures) has been developed for observation of metal corrosion. XAFS spectra were obtained with a special electrochemical cell to elucidate pitting: change of concentrations and structures of ions near the interface of solution and metal. It has been successfully shown that the concentrations of Cr and Br are linearly dependent on the distance from the interface. Also, salt formation at the interface and the hydrolysis reaction far from the interface are indicated.

Use of Artificial Pits to Investigate Conditions for the Growth and Repassivation of Open Macroscopic Corrosion Pits in Stainless Steels

Two different artificial pit configurations were developed to investigate the conditions required for continued growth of open macroscopic corrosion pits in stainless steel sheets. To reproduce the conditions in growing real pits in oxidising environments, the pit growth was activated under anodic polarisation either by injecting concentrated chloride solution into the pit or by initially filling the pit by chromic chloride crystals (CrCl 3 .6H 2 O). Experiments were made on sheet specimens of stainless steels of type UNS S31603 or UNS S31254 in bulk solutions containing chloride and/or sulphate ions. Various aspects of the test arrangements and pitting of stainless steels are discussed, including the electrolyte composition within the pits and the IR-drops both inside the pits and in the bulk solution. It is demonstrated that using the artificial pit configurations the effects of the main variables affecting the conditions for growth and repassivation of open corrosion pits can be investigated quantitatively, including electrode potentials and composition of the bulk solution. It is concluded that for continued growth of corrosion pits with a large opening to the bulk solution, a strongly oxidising environment is required, and that sulphate ions are fairly inefficient in stopping the growth of propagating pits.

Aggressive effects of pitting “inhibitors” on highly alloyed stainless steels

Anions such as sulphate inhibit pitting of stainless steels by raising the pitting potential. One might, therefore, expect sulphate to raise the critical pitting temperature (CPT), below which no stable pitting occurs at any potential. Surprisingly, this expectation turns out to be false. Addition of 0.5M Na 2SO 4 to 1M NaCl lowers the CPT of type 904L steel from 49 to 38 °C. Since metastable pitting of this alloy occurs even at room temperature, the effect of sulphate concerns the ability of metastable pits to become stable. Microscopic examination reveals that the stabilization is associated with the lacy metal cover that develops over the pit. When the inhibitor is present, the enhanced passivation reduces the porosity of the pit cover and helps the pit to retain its local environment.

高温塩化物水溶液中におけるステンレス鋼の孔食に及ぼす窒素およびモリブデン化学種の影響

高温塩化物水溶液中におけるステンレス鋼の孔食に及ぼす窒素およびモリブデン化学種の影響

Stainless Steel Pitting in Thiosulfate Solutions with Electrochemical Noise

Abstract Resistance of stainless steels (SS) to generalized corrosion is provided by growth of a protective thin film of mixed oxides. In aqueous solutions, impurities can destroy this passive laye...

Surface Roughness and the Metastable Pitting of Stainless Steel in Chloride Solutions

Abstract The effects of surface roughness on metastable pitting susceptibility of type 304 (UNS S30400) stainless steel (SS) in chloride (Cl−) solution and the transition to stable pitting corrosion were investigated. A smoother surface finish reduced the frequency of metastable pitting because the number of metastable pit sites available was reduced. Once formed, however, a metastable pit had a greater probability of achieving stable pit growth if the surface was smoother. Observations were rationalized qualitatively in terms of the geometry of the available metastable pit sites and their ability to establish a diffusion-controlled dissolution rate.

The use of very weak galvanostatic polarization to study localized corrosion stability in stainless steel

Galvanostatic anodic polarization is sometimes used to study pitting of stainless steel, but has never been very popular despite the clear and interpretable results that can be obtained. In this paper it is shown that the galvanostatic technique provides a rapid way of assessing the relative performance of different heats of a particular stainless steel, or the stabilizing effects of inclusions and sulphur anions on pit growth. It is suggested that the importance of slow scan rate in potentiodynamic tests has been exaggerated, and that the most appropriate combination of test methods is a relatively rapid potentiodynamic scan and a galvanostatic test (or series of tests) at very low anodic current, to test the stability of localized corrosion over a relevant time scale. Remarkable evolutionary phenomena occur when a population of active pits is grown by a low applied current, and these dynamics must be relevant to the long-term performance of passive alloys in practice.

The pitting of stainless steel under a rust membrane at very low potentials

Stable pitting of Type 304L stainless steel has been observed repeatedly at potentials as low as −140mV(SCE) in the presence of a rust membrane, produced by corroding an electroplated iron layer. The onset of stable pitting in the ‘rusted’ specimens coincided with the onset of metastable pitting events on normal stainless steel surfaces. The rust layer acts as a super-crevice, combining the anion-selective action proposed by Sato with a low ionic resistance, and prevents or greatly delays repassivation of metastable pits. Such a layer is especially effective at low chloride concentrations, where conventional crevice corrosion is absent or propagates at a very low rate owing to the high solution resistance to current flow out of the crevice. These results provide an explanation for freshwater microbial corrosion without invoking sulphate-reducing bacteria or other sources of aggressive corrodents.

Role of Sulphur Inclusions on the Pitting of Stainless Steels in Chloride Media

Role of Sulphur Inclusions on the Pitting of Stainless Steels in Chloride Media

What progress in the understanding of microbially induced corrosion has been made in the last 25 years? A personal viewpoint

The last 25 years have seen a number of significant advances in the understanding of microbially induced corrosion. Developments in corrosion theory and microbiology have been brought together to explain the anaerobic corrosion of iron and carbon steel in electrochemical terms. Accelerated pitting of stainless steels associated with micro-organisms has been described and the mechanisms substantially elucidated. Practical techniques for monitoring and control of microbiological activity in industrial systems have become more sophisticated, especially biofilm monitoring. The advances in the above areas have been outlined in this paper together with other fields in which, curiously, little progress has been made in recent years.