CORROSION REVIEWS

Published by De Gruyter
Online ISSN: 2191-0316
Publications
Article
Based on a combination of corrosion tests and surface analysis, a screening procedure was developed to evaluate the inhibitive efficiency of inhibitor pigments to be used in organic coatings for application on the aircraft aluminium alloy AA2024. In addition, the influence of chromate-free inhibitor pigments on the properties of organic coatings has been investigated using a water based epoxy model primer.
 
Heat Treatment used for corrosion-fatigue testing of DSS's.
Article
Corrosion fatigue of heat treated duplex stainless steel in paper machine white waters was investigated. Standard corrosion fatigue tests were conducted using compact tension specimens by measuring the crack growth with the number of fatigue cycles. Stress intensity change was calculated for crack growth under realistic environments. Results indicated increased effect of microstructural changes on the threshold stress intensity for crack propagation and crack growth rates as compared to the increase in chloride ion concentration.
 
Article
The present article reviews the feasibility of electrochemical noise (ECN) measurements as a corrosion probe for monitoring corrosion changes on stainless steel 304L (UNS 30403). Controlled tests for ECN and weight loss measurements were conducted in 10% NaCl solution for stainless steel 304L (UNS 30403). Corrosion behavior was established by comparing and analyzing ECN signals, from both time and frequency domains, to weight loss and visual observations. Conventional data treatment of the ECN parameters in both time and frequency domains yielded the same results, which related to physical weight loss and pitting observations. According to the findings of this study, electrode biasing occurred in all tested conditions. The source of biasing is unclear at the moment. However, it is believed that minor differences between the two "nominally identical" electrodes (e.g. surface finish, size, microstructure, temperature variations, solution composition) may be responsible for its occurrence. No definite explanation is available to justify the persistency of biasing through out a test.
 
Article
In order to understand the corrosion behavior of high-velocity oxygen-fuel (HVOF) TiAlNb coatings in molten Zn-0.2 wt.% Al, the different kinds of TiAlNb coating were deposited on 316L stainless steel substrate and the corrosion tests in molten zinc were carried out. The coating morphologies, phase composition, and characteristics of HVOF TiAlNb coatings at different stages of immersion time were studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectrometry (EDX). The results indicated that the HVOF sprayed TiAlNb intermetallic compound coatings have excellent corrosion resistance to molten zinc. The corrosion type of the HVOF TiAlNb coatings in molten Zn-0.2 wt.% Al is pitting corrosion and crack corrosion. In the whole corrosion stage of molten Zn-0.2 wt.% Al, the corrosion time has no effect on the phase compositions of the HVOF TiAlNb coatings.
 
Article
One of the promising applications of magnesium and magnesium alloys is their use as biodegradable implants in biomedical applications. The pH around an orthopedic implant greatly affects the degradation kinetics of biodegradable Mg–Ca alloys. At the location of a fracture, local pH changes, and this has to be considered in the optimization of implant materials. In this study, the effect of the pH of a physiological buffer on degradation of a Mg–0.8Ca alloy was studied. The pH of Hank’s balanced salt solution (HBSS) was adjusted to 1.8, 5.3 and 8.1. Degradation of a Mg–0.8Ca implant was tested using immersion test and electrochemical techniques. Immersion tests revealed an initial weight gain for all samples followed by weight loss at extended immersion time. Weight gain was highest at acidic pH (1.8) and lowest at alkaline pH (8.1). This was in agreement with results from electrochemical polarization tests where the degradation rate was highest (7.29 ± 2.2 mm/year) at pH 1.8 and lowest (0.31 ± 0.06 mm/year) in alkaline medium of pH 8.1. The pH of all HBSS buffers except the most acidic (pH 1.8) reached a steady state of ∼pH 10 at the end of the two-month immersion period, independent of the initial pH of the solution. Corrosion products formed on the sample surfaces were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and X-ray diffractometry (XRD), revealing the formation of magnesium and calcium phosphates with distinct morphologies that were different for each of the pH conditions. Thus, pH of physiological buffers has a significant effect on the degradation and corrosion of Mg–Ca alloys used for biomedical applications.
 
Article
The internal cleanup of pipelines with pigging systems to remove organic, inorganic and microbiological scales is being used worldwide. In this work, the experiments were carried out under turbulent flow (Re = 46,300) at 25°C using a seawater looping system. Prior to evaluating the efficacy of the tested pigs, coupons were kept in contact with the seawater system for eight days in order to allow biofilm formation. Biofilm microbial population was quantified before and after the pigging processes. After testing five consecutive pigging processes of three different materials, the results showed the following removal performance for aerobic, iron-oxidizing, anaerobic, sulfate-reducing bacteria and filamentous fungi populations, respectively: PIG1 (D-20 foamy PIG, wrapped with the soft side of Velcro® material, handmade) - 68, 67, 68, 100 and 100%; PIG2 (D-20 foamy PIG wrapped with the rough side of Velcro® material, handmade) - 77, 68, 67, 100 and 89%; PIG3 (D-50 foamy PIG wrapped with the rough side of Velcro® material, industrially manufactured) - 83, 93, 79, 100 and 100%. On the other hand, the most effective PIG in removing biofilms caused the greatest deterioration of the metallic surfaces, as follows: PIG1 - 1.40mm/year; PIG2 - 1.70mm/year: PIG3 - 4.60mm/year.
 
Article
Stainless steel has proved to be an important material to be used in a wide range of applications. For this reason, ensuring the durability of this alloy is essential. In this work, pitting corrosion behaviour of EN 1.4404 stainless steel is evaluated in marine environment in order to develop a model capable of predicting its pitting corrosion status by an automatic way. Although electrochemical techniques and microscopic analysis have been shown to be very useful tools for corrosion studies, these techniques may present some limitationus. With the aim to solve these drawbacks, a three-step model based on Artificial Neural Networks (ANNs) is proposed. The results reveal that the model can be used to predict pitting corrosion status of this alloy with satisfactory sensitivity and specificity with no need to resort to electrochemical tests or microscopic analysis. Therefore, the proposed model becomes a useful tool to predict the behaviour of the material against pitting corrosion in saline environment automatically.
 
Article
This paper investigated optimization of corrosion inhibitory attributes of mixed cocoa pod- Ficus exasperata (CP-FE) extracts towards mild steel in 1.5 M HCl using central composite design. Potentiodynamic polarization, linear polarization resistance and electrochemical impedance spectroscopy measurements were used for the electrochemical study. The result revealed maximum inhibition efficiency of 91.52% at temperature, inhibitor concentration, time and acid concentration of 50 °C, 5 g/L, 144 h and 0.2 M, respectively with R ² value of 0.9429. Central composite design predicted optimum point of 70.37 °C, 3.81 g/L, 127.37 h and 0.22 M. Potentiodynamic polarization revealed extract to be mixed-type inhibitor with anodic prevalence. Electrochemical impedance spectroscopy showed that corrosion inhibition occurred via adsorption of CP-FE molecules on active sites of MS surface. Scanning electron microscopy images revealed protection of mild steel surface by adsorbed molecules of CP-FE extracts. Fourier transform infrared revealed presence of carboxyl (–COOH), unsaturated (–C-C–) and hydroxyl (–OH). Energy dispersive spectroscopy revealed presence of high iron composition on mild steel surface in the presence of mixed CP-FE extract proving its corrosion inhibition efficiency in 1.5 M HCl. Atomic adsorption spectroscopy revealed loss of Fe ²⁺ into free HCl solution. Generally, extract from mixed CP-FE was found as effective corrosion inhibitor for mild steel in 1.5 M HCl solution.
 
Article
Mg-11Li-1.6A1 alloy is used in aerospace and in several other applications. An understanding of the corrosion aspects of the alloy in various chloride solutions will greatly help in devising suitable protective schemes to enhance the service life. Polarisation, gasometry, X-ray diffraction and atomic absorption spectrophotometry methods have been used to investigate the corrosion parameters, hydrogen evolution rate, dissolution rate, dealloying behaviour and the nature of corrosion products. A comparison of the dissolution rates shows that AAS provides a higher value than the electrochemical measurements. The reasons for this disparity have been analysed. The applicability of these techniques in resolving certain issues and the complementary nature of results from certain techniques are revealed in this communication. Above all 'delithiation', a new phenomenon observed during the study, is also highlighted.
 
Article
The cold rolled AISI-321 austenitic stainless steel after prolonged cathodic polarizations in an aqueous electrolytic medium of sulfuric acid containing arsenic (V) oxide [0.1M H2SO4 + 1g/l As 2O5(V)] undergoes structural transformation involving macroscopic buckling, permanent bending, and eventual tearing along the edges. Microscopically, dislocation networks, stacking faults, and martensitic phases are observed with prolonged H-charging. When compared to the charging of high Fe-C austenites, Fe-C system shows surface striations whereas none is observed with the stainless steel. While buckling and bending are also observed in Fe-C alloys, lathes-like α'-martensites are observed in stainless steel, while acicular types in the Fe-C alloys. The optimal cathodic polarization necessary to provoke structural deformation for Fe-C alloy is within 2200 A/m2, while it is in the range is 50-5000 A/m2 for Type-321. Mössbauer effect measurements (MEM) show that both materials decompose with retained austenite in proportion to degree of hydrogen charging, with an upper limit of 63% transformation in Fe-1.5C, while a mere 13% in the case of AISI-321. The Fe site in the formed martensites, and retained austenite are not affected by the degree or extent of the austenitic decomposition.
 
Article
Cyclic corrosion, consisting of carburization in Ar+4% CH4+3% H2 for 1 h and oxidation in air for 1 h, of Ni-base in a wrought alloy, Hastelloy-X, was investigated at 1000°C to understand the significant metal loss occurring in fuel injection nozzles of gas turbine combustor operated using natural gas. The mass gain of cyclic corrosion was relatively low up to about eight cycles of corrosion by formation of a Cr2O3 scale in each oxidation stage, but it increased rapidly due to formation of a Fe-and Ni-rich oxide scale as the number of corrosion cycles increases. The Cr content in the subsurface region rapidly decreased under the cyclic corrosion condition compared with a continuous single oxidation or carburization, which resulted in the formation of non-protective Fe-and Ni-rich oxide scale in a small number of corrosion cycles. The formation of a Cr3C2 scale from the protective Cr2O3 scale in the carburization stage was detrimental for the oxidation resistance of Hastelloy-X and was considered to have a similar effect to spallation of a Cr2O3 scale; therefore, it accelerated Cr consumption from the alloy subsurface region.
 
Article
The kinetics of biofilm formation on AISI-1020 carbon steel coupons, as a function of dissolved oxygen concentration, was studied in 8-day experiments. In addition, the weight loss and electrochemical parameters, galvanic current and corrosion rate of the coupons were also taken into account. The assays were carried out under turbulent flow (0.48 m3/h, Re = 9,700), using a seawater looping system connected to a 30-1 tank, all in PVC. The results have shown that a reduction in DO concentration from 6.40 to 0.08 mg/l has led to microbial populations in the range from: (6.03 ± 2.9)×107 to (5.75 ± 2.8)×104 cells/cm2 (aerobes bacteria); (6.03 ± 2.9)×107 to (1.05 ± 0.6)×103 cells/cm2 (anaerobes bacteria); (5.75 ± 2.7)×107 to (1.91 ± 1.0)×105 cells/cm2 (iron-oxidizing bacteria); (2.19 ± 1.2)×103 ufc/cm2 to below detection (fungi); and (1.51 ± 0.7)×106 cells/cm2 to below detection (SBR). In addition, corrosion rates have ranged from 14.0 to 0.98 mm/y under the same conditions.
 
Article
A study of the corrosion kinetics of a 12Cr-1Mo-0.3V-0.2C stainless steel, at temperatures between 973K and 1273K, was carried out. The kinetic laws that rule the process and the corresponding constants for each temperature were determined. The relations k = f(T) and n = f(T) were also established for the kinetic laws obtained (yn= k). The results were justified by the microstructural changes that were observed during the heat treatment, with an acceptable corrosion behaviour of the materials being observed when the materials were tested at temperatures below 973K.
 
Article
Heat resistant steel 13CrMo4 4 steel is extensively employed in fossil fuel-fired boilers. Its temperature of operation is rarely higher than about 525°C. In this study, the high temperature behaviour of this steel is being investigated under isothermal conditions, ranging from 400 to 800° C for a maximum exposure time of 300 hours in air. The oxidation results show that this alloy is able to withstand temperatures up to 600° C thanks to the formation of an oxide scale mainly based on haematite oxides, giving rise to a parabolic kinetics as a result of a solid state diffusion process. However, oxidation at 800° C brings about spalling of the oxide scale, changing from a parabolic to a paralinear law.
 
Article
The corrosion behavior of 15CrMo used for water-wall tubes was studied in various urea-containing solution to determine the corrosion problem of water-wall tubes caused by urea in a coal-fired power plant. Urea decomposition tests, together with corrosion experiments, were carried out. The temperature was 320 °C, and the concentrations of urea were 70, 140, 280, 560 and 840 mg/L. Weight loss experiments and surface analysis indicated that the corrosion of 15CrMo steel is mainly manifested as localized corrosion. The corrosion rate of 15CrMo steel increased with the increase of urea concentration, and the maximum value reached 0.686 mm/y (mm per year) when the urea concentration was 840 mg/L. Electrochemical analysis suggested that the corrosion rates of 15CrMo were enhanced substantially by urea decomposition products. The results of UPLC-ESI-MS, infrared spectroscopy and X-ray diffraction showed that urea solution produced corrosive ions NH 2 COO ⁻ during the decomposition process, which caused the corrosion of 15CrMo. Results provided evidence as relevant explanation for the corrosion behavior of 15CrMo in urea solution.
 
Article
Slow strain rate tests (SSRT) were conducted to determine the susceptibility of the 17-4-PH type steel to stress corrosion cracking (SCC) in simulated low pressure (LP) steam turbine environments. Environments tested included solutions of NaCl, NaOH and Na2SO4 at different pH values, electrochemical potentials, concentrations, mixtures and strain rates at 95°C. It was concluded that this steel was susceptible to SCC in acidic NaCl solutions and with the application of both anodic and cathodic potentials and lowering of the strain rate. It is concluded that both hydrogen embrittlement and anodic dissolution mechanisms are responsible for the SCC susceptibility.
 
Article
Sm2(Co,Cu,Fe,Zr)17 are the best high-temperature permanent magnets because of their high Curie temperature (800°C-850°C). However, irreversible and unacceptable coercivity losses retard their use in applications at temperatures over 550°C. The coercivity loss has been correlated with poor oxidation resistance at high temperatures. The current research progress on the effect of oxidation and its prevention, for 2:17-type magnets, is reviewed. Oxidation in air at 500°C-700°C causes the magnets to form three regions: (1) an external oxide scale mainly consisting of (CoxFe1-x)3O4, (2) a thicker internal oxidation zone where the typical cellular precipitation (2:17R cell and 1:5H cell boundary) structure has been completely collapsed due to the Sm oxidation into Sm2O3, and (3) an oxidation-free zone where the cellular precipitates remain unchanged in lattice structure. No unacceptable coercivity loss is seen in the oxidation-free zone. Its thickness can be impressively increased within the magnets at high temperature, when they are covered with surface diffusion barriers for oxygen from the atmosphere, such as thin films of Cr2O3, Al2O3, and the metals with the ability to thermally grow these oxides.
 
Article
This study describes corrosion behaviour and microstructure evolution of 17-4 PH stainless steel foam, which was produced for biomedical implant applications. 17-4 PH stainless steel foam was produced by the space holder-sintering technique. The effect of boron addition, aging, sintering temperature and sintering time on the corrosion behaviour and microstructure of the 17-4 PH stainless steel foam was investigated. Microstructure of the 17-4 PH stainless steel foams was examined by using scanning electron microscope (SEM) and optical microscope. The corrosion behaviour of the 17-4 PH stainless steel foam was investigated by using neutral salt spray (fog) and accelerated aging tests. The 17-4 PH stainless steel foams were exposed to salt spray solution, which consisted of 5 % NaCl with pH of 6.68, in a closed cabin at 35 °C. The surface of the foams after the corrosion test was observed by optical microscope and the digital photographs were analysed by an image analyser. The corrosion resistance of boron-added foams was higher than boron-free 17-4 PH stainless steel foams. Aging heat treatment slightly decreased the corrosion resistance of the 17-4 PH stainless steel foams. Increasing sintering temperature and sintering time increased the corrosion resistance of the stainless steel foams.
 
Article
The British sloop of war HMS Swift sank in the Deseado estuary (Santa Cruz, Argentina) on March 13 th, 1770. At present this archaeological site constitutes one of the most important South American underwater cultural heritage. The main goal of this work has been to understand the natural processes which participate in the formation and evolution of underwater sites, with particular emphasis on biodeterioration aspects produced by biofouling communities and marine wood borers. Since both types of organisms have played an important role in the evolution of this site, it has been decided to start experimental assays and periodical monitoring, based on the use of acrylic and wood micro panels. Through these experiments we expect to clarify basic biological and ecological aspects of these communities and their action on several materials and artifacts present at the Swift site. Additionally, we have started some studies on the sedimentary characteristics and on some human impacts on the site. This interdisciplinary approach will allow a better organization of the excavation tasks, giving priority to those sectors which are more prone to natural destruction.
 
Article
One of the most interesting alternatives for replacement of hard chrome plating is tungsten carbide thermal spray coating applied by the high velocity oxy-fuel (HVOF) process which presents a safer, cleaner and less expensive alternative to chromium plating. The objective of this research is to compare the influence of the tungsten carbide-17cobalt (WC-17Co) coating applied by high velocity oxy fuel (HVOF) process with that of hard-chromium electroplating on the fatigue strength and abrasive wear of AISI 4340 steel.
 
Article
One of the most interesting alternatives for replacement of hard chrome plating is tungsten carbide thermal spray coating applied by the high velocity oxy-fuel (HVOF) process which presents a safer, cleaner and less expensive alternative to chromium plating. The objective of this research is to compare the influence of the tungsten carbide-17cobalt (WC- 17Co) coating applied by high velocity oxy fuel (HVOF) process with that of hard-chromium electroplating on the fatigue strength and abrasive wear of AISI 4340 steel.
 
Article
In this paper the influence of variable contents of Nb and Ti in experimental 30Ni-18Cr-0.3C (wt-%) cast steel on its resistance to, carburization has been presented. In investigated alloys the contents of Nb and Ti were in the range 0 to 1.8 and 0 to 1.0 wt-% respectively. The carburization has been carried out at 900 degreesC for 300 h at a carbon potential of C-p = 0.9%. The resistance to carburization has been assessed by gravimetric and hardness measurements. The regression equation describing a mass increment of the specimen and the thickness of the carburized zone as a function of chemical composition of cast steel has also been determined. The presented equations show that single and/or combined increase in contents of additions has a beneficial effect on inhibition of carbon diffusion in the alloy.
 
Article
The fouling community was examined from May 1991 to April 1992 at Mar del Plata harbor, Argentina. In this work the recruitment trends of macrosessile foulers and the seasonal developmental sequence of the community for one year were analyzed. Multivariate cluster analysis revealed two underlying trends of recruitment, one from late autumn to spring, and the other from summer to early autumn. Ciona had an important functional role in the community, as an adult might enhance the arrivals of some species as secondary space recruiters, but it was also a good interference competitor for primary space occupiers. During summer, the larvae of Ciona were poor competitors for seasonal primary space occupiers. This situation enhances the invasion of calcareous exoskeleton organisms, such as Balanus and Hydroides. Some differences between the potential arrivals of propagules and their contribution to the developing community were found. This community developed a pathway similar to that of other fouling communities with solitary ascidian species. Perturbations to diminish or exclude the foundation species abundances as Ciona, Balanus and Hydroides would be necessary to modify the early community structure.
 
Article
The corrosion field experienced a rapid growth in knowledge and innovations in the last decade. In this paper, a bibliometric analysis was applied to evaluate the global scientific production of corrosion papers (46,384 pieces) from 1992 to 2007 in all journals of all the subject categories of the Science Citation Index Expanded (SCIE) compiled by the Institute for Scientific Information (ISI), Philadelphia, USA. The analysis of the published outputs showed that research on corrosion increased steadily over the past 16 years and the researchers from the EU, the USA and China contributed greatly to the rise in publications. Synthetically analyzing the information including international cooperation, subject category, distribution of journals, document type, document language and author keywords, the development of corrosion research over the past 16 years has been visualized and several key findings were provided. This bibliometric method can help relevant researchers realize the panorama of global corrosion research, and establish the further research direction.
 
Article
Honeycomb bonded assemblies have been used extensively in aerospace because they are extremely structurally efficient, particularly in stiffness critical designs. However, honeycomb assemblies are challenging to build and some have had a rather dismal in-service record. This paper will discuss the difficulties involved in building honeycomb assemblies and will highlight some of the in-service problems experienced by both military and commercial users. Fabrication difficulties include blown core, core migration, and skin-to-core unbonds. In-service problems are usually a result of liquid water ingression into the honeycomb cells resulting in core corrosion (aluminum core), node bond and skin-to-core degradation and occasionally, face sheet separation. Alternate design and construction concepts to honeycomb bonded assemblies will be presented, with an emphasis on integrally cocured unitized structure.
 
Article
The present work aims to provide a better understanding of the effects of corrosion and the associated corrosion-induced hydrogen embrittlement on the mechanical behaviour of the 2024 aircraft aluminium alloy. Evidence is provided of the corrosion-induced hydrogen embrittlement of the material and the tensile, fatigue and damage tolerance behaviour of precorroded specimens are discussed under the viewpoint of a synergistic effect of corrosion and corrosion-induced hydrogen embrittlement. The results presented rely on an extensive experimental investigation involving mechanical testing, metallographic and fractographic analyses as well as measurements of the hydrogen uptake during the corrosion process.
 
Article
This paper describes the corrosive effect on aluminum 2024-T3 alloy of fire retardant products present in the interiors of the general aviation aircraft. To this end, various existing fire retardant products were evaluated from the point of view of corrosiveness when in contact with the most commonly used aluminum alloy in aircraft, i.e., 2024-T3. Extensive experiments were carried out, varying different parameters, i.e., temperature and humidity, by the sandwich test technique. The results were statistically analysed, comparing the specimens with and without fire retardant products. The results prove conclusively that the existence of a few halogen based salts might be the main source for inducing corrosion. The elimination of this chemical from the cabin interior can reduce the probability of corrosion.
 
Article
Corrosion resistances and microstructures of welding seams of SAF 2205 duplex phase stainless steels welded by the AWS E316-15 austenite welding material, the parent alloy (SAF 2205 alloy) and the 22.9.3.LT patent welding material are compared. It is found that the corrosion resistance of the welding seam made by AWS E316-15 is slightly lower than that of 22.9.3.LT due to lower ferrite percentage and the larger grain sizes, while the worst corrosion resistance among the three welding materials is present for the welding seam made by the parent alloy.
 
Article
The corrosion behavior of duplex stainless steel 2205 DSS and 2507 DSS in simulated flue gas condensate of a waste incineration power plant at 180 °C was compared by micro-area electrochemical testing, surface and weight loss analysis. The results showed that the corrosion resistance of the two stainless steels decreased with the increase of Cl ⁻ concentration. After 48 h of corrosion, when the Cl ⁻ concentration was not less than 6 g·L ⁻¹ , active sites where current density increased suddenly appeared on the surface of 2205 DSS, accompanied by the obvious increase of surface roughness and the weight loss. The lowest Cl ⁻ concentration that caused the appearance of active sites on the surface of 2507 DSS was 20 g·L ⁻¹ , with less surface corrosion products and lower degree of general corrosion.
 
Article
As a nondestructive and sensitive method, electrochemical impedance spectroscopy (EIS) can be used to investigate the passivation and breakdown of passive films on steel. In this study, EIS, combined with slow strain rate test and scanning electron microscopy, was employed to study the stress corrosion cracking (SCC) behavior of 2205 duplex stainless steel in 0.5 m sulfuric acid solution under hydrogen-charging conditions. Results showed that the corrosion resistance of passive film on the hydrogen-charged specimen was lower than that for the specimen with no hydrogen charge. Hydrogen-induced cracking was evident after the specimens had been charged for 24 h. The phase shift in EIS, calculated from frequencies between 0.1 and 10 Hz, could be used to monitor the SCC process.
 
Article
The continuously increasing demand for stainless steels with enhanced corrosion resistance and mechanical properties has resulted in an increased interest in ferritic-austenitic stainless steels (DSS). The main advantage of DSS as compared to austenitic stainless steels is the better resistance to stress corrosion and the higher strength. A higher tensile strength can give construction advantages, e.g. on offshore platforms where high strength and a low total weight are of great importance. Sandvik SAF 2507 (UNS S32750) is a ferritic-austenitic stainless steel suitable for service in highly corrosive environments. It belongs to the so-called super-duplex stainless steels with a pitting resistant equivalent PRE=Cr+3.3Mo+16N equal to or above 40. Typical applications are seawater handling and process systems for the oil and gas industries, seawater cooling, piping systems for refineries and petrochemical plants where the properties of standard duplex. steels like Sandvik SAF 2205 (UNS S31803) are not sufficient. Mechanical properties and corrosion properties have been evaluated for TIG, MMA and submerged-arc welds in tubes and plates with thicknesses from 1.65 mm up to 18 mm. Experimental procedures and test results are presented in the form of welding procedure specifications and procedure qualification records.
 
Article
Transmission electron microscopy (TEM) was employed to investigate the dissolution behavior of nanocrystalline grain boundary T1 precipitates in Al-3Cu-2Li. These grain boundary T1 plates exhibit an orientation relation with matrix, with the (1-11)α-Al parallel to (0001)T1 and [022]α-Al parallel to [10-10]T1, which is similar to the orientation relationship of T1 plates formed within grains. TEM studies showed that these grain boundary T1 plates react readily in moist air. As a result of the localized dissolution, the Cu-rich clusters form onto T1, which is consistent with the localized dissolution behavior observed in nanocrystalline S phase in Al-Cu-Mg.
 
Article
Lately the principal producers of honeycomb blocks are oriented to convert their production on the usage of aluminium alloy treated with chemical products free from Chromium either exavalent or trivalent. On the other hand for environmental protection reasons, all the conversion treatments are pointing to no rinse product (with no kind of treatment of hazardous waste) which are total consumption products and they are usually applied with coil coating technologies. In the following article there will be a complete description of the results obtained with an experimental study on surface treatments of aluminium alloys using no rinse products based on Fluorine, Titanium and Zirconium compounds supplied by Henkel Surface Technologies using samples with different conversion layer grammage: 5,2mg/m2, 10,0 mg/m2 e 16,9 mg/m2. Corrosion resistance has been evaluated by using electrochemical spectroscopy of impedance (E.I.S.) in a 3,5% in weight NaCl solution inflated with air, simulating a marine environment. The second part of the article will deal with the evaluation of the surface energy of the conversion layer by measuring the contact angle of a polar liquid (water) and not polar liquid (di-iodine methane) with an optical instrument and a mathematical interface for the data conversion.
 
Article
To investigate the effect of interaction between two single-Si 3 N 4 particle-impingements on the repassivation of 304 stainless steel in a simulated groundwater, the corrosion current peaks of the samples during the impingement were recorded, and the micro-hardness of the substrate around the crater was tested. The results indicated that significant interactions between the two impingements were observed only when the value of distance-diameter ratio ( L/d ) was less than 1.5. With L/d being less than 1.5, the corrosion current peaks and mass losses due to the second impingements were higher than those of the first ones, and the re-passivation rates of samples during the second impingements were lower than those of the first impingements. Simultaneously, the microhardness of the substrate between the two craters was higher than that of the surface around one single crater with the same distance-diameter ratio. The mechanisms of how the L/d ratio influenced the interaction between the two impingements are also discussed.
 
Article
Pitting initiation on 304 stainless steel grades was investigated in alternating temperature pore solutions to simulate pitting on stainless steel rebar in a tropical marine environment. The results suggested that a larger amplitude of alternating temperature heavily doped the passive film, reduced the film’s thickness and increased the (Fe3+ox + Fe3+hy)/Fe2+ox and Cr3+hy/Cr3+ox ratios in the film. Alternating temperatures more significantly degraded the passive film and intensified the pitting sensitivity on the stainless steel when compared with the average temperatures of the alternating temperature cycles. More pitting initiation sites were observed on the samples that experienced the 22–60 °C and 22–70 °C alternating temperature cycles than their counterparts in 50 °C and 60 °C solutions, respectively.
 
Article
The oxidation kinetics of three modified AISI 316 steels has been studied at the temperature range of 700 to 900 degreesC in static air, by substituting vanadium for molybdenum and chromium. As the amount of vanadium is increased (and chromium content decreased) the weight gain of the steel increases for a given temperature following a parabolic rate law. As the temperature is increased for a given steel, the oxidation resistance is remarkably affected, showing the disadvantage of the replacement of molybdenum and chromium by vanadium. Activation energy calculations for the modified steels indicate that the steel containing both the larger amount of vanadium and lesser chromium content requires the least amount of energy for oxidation. The decline in the oxidation properties is attributed to the formation of a Fe - Cr type spinel that starts growing steadily on the metal surface that subsequently undergoes phase transformation into a non adherent oxide scale.
 
Article
Stainless steel is known for its superior corrosion resistance in industrial applications. In this work, corrosion modeling of stainless steel 316L is presented using artificial neural networks. The experimental setup consists of a loop containing stainless steel elbow with simulated seawater of known concentration continuously flowing at a specific flow rate, thus allowing to study the effect of flow dynamics and salt concentration on corrosion. Electric field mapping setup is used to collect the voltage and current information along with the temperature of the elbow section. In addition to modeling, characteristics of the observed scale deposits are also studied in-depth and briefly reported in this work.
 
Article
Toxic alloying elements were added to a piece of 316 L stainless steel (SS) in order to promote a toxic passive layer and protect it against biocorrosion in sea water. In order to characterize the modified stainless steels, open circuit potential monitoring versus exposure time and polarization techniques were used. In addition, the chemical composition and thickness of the passive layer of the modified SS was characterized by using electron spectroscopy for chemical analysis. SEM microanalysis and microstructural characterization of the modified SS were performed in order to determine the location of doped elements. The results from the electrochemical tests and microbiological analyses performed on different doped SS immersed in natural sea water showed that the passive layers were enriched with the toxic elements and their behavior depends on both the nature of the poison alloying element and the presence or absence of bacteria in the water.
 
Article
Anodic protection (AP) is one of the corrosion control methods that has been widely used in the manufacture, storage, and transport of sulfuric acid. The present paper gives a brief review of the history, some applications, and a case study of failure causes and remedial actions of AP in a sulfuric manufacturing plant. The AP system consists of a direct current source, cathodes, reference electrodes, and signal conditioning electronics. In a sulfuric manufacturing plant, for AP of 316L piping (as an anode), platinized titanium (Pt/Ti) and Hastelloy B-2 were used as reference and cathode electrodes, respectively. After seven years of operation of the AP system in the sulfuric acid plant, a section of the protected pipelines has severely corroded. The study of the system showed that the reference electrodes, which were titanium-electroplated with platinum, lost their stability in the acid with the loss of coating and caused overprotection. However, the system could not control the pipe’s potential in the AP situation. In this condition, accelerated corrosion of the cathodes and pipes has also occurred.
 
Article
Motivated to reduce the costs incurred by corrosion in material science, this article presents a combined model based on artificial neural networks (ANNs) to predict pitting corrosion status of 316L austenitic stainless steel. This model offers the advantage of automatically determining the pitting corrosion status of the material. In this work, the pitting corrosion status was predicted, with the environmental conditions considered, in addition to the values of the breakdown potential estimated by the model previously, but without having to use polarization tests. The generalization ability of the model was verified by the evaluation using the experimental data obtained from the European project called “Avoiding Catastrophic Corrosion Failure of Stainless Steel”. Receiver operating characteristic space, in addition to area under the curve (AUC) values, was presented to measure the prediction performance of the model. Based on the results (0.994 for AUC, 0.980 for sensitivity, and 0.956 for specificity), it can be concluded that ANNs become an efficient tool to predict pitting corrosion status of austenitic stainless steel automatically using this two-stage procedure approach.
 
Article
In the present study, the effects of aging and formation potential on the semiconducting behavior of AISI 321 stainless steel as well as the kinetics of the early stages of pitting are discussed. The donor and acceptor densities decrease with increasing formation potential. The steady-state passive film thickness and the coefficient of oxygen vacancies are estimated. The electrode polarization at higher anodic potentials causes the increase in the rate of pit initiation and slows down the growth rate of passive film. Also, the openness of the pits and their coalescence are highly promoted with the increase in the applied potential.
 
Top-cited authors
Andrej Atrens
  • The University of Queensland
Kamachi Mudali U.
  • VIT Bhopal University
Noam Eliaz
  • Tel Aviv University
Baldev Raj
  • Indira Gandhi Centre for Atomic Research
Michael Schorr Wiener
  • Autonomous University of Baja California