Severe Localized Corrosion Research Articles

End patch loading behavior and strengthening of locally corroded steel I-beams

One of the problems that affect steel bridges is the deterioration of the beam ends due to local corrosion, thus reducing their end patch loading resistances. A recent paper by the authors has studied the individual influences of web and flange corrosions on the end patch loading behavior of steel I-beams. This paper presents further experimental results for the specimens with combined web and flange corrosions, since they coexisted in many cases. Two common types of sliding plate bearings were considered in this study, i.e., flat and curved plate bearings. The test results show that the end patch loading resistances of the specimens with flat plate bearings are higher than those of the corresponding specimens with curved plate bearings, especially for the corroded beams. With regard to the specimens with flat plate bearings, the combined effect of web and flange corrosions on the end patch loading resistance is less than the sum of the effects of each alone. In addition, a novel strengthening method is developed for the steel beams affected with severe local corrosion. The corroded beam end is first strengthened by welding a pair of stiffeners and is then partially encased with high-strength grout. It is found that the end patch loading resistance of the corroded beam can be significantly increased by the stiffeners and can be further enhanced with the encasement of high-strength grout. The proposed method can minimize the traffic interruption and also prevent the bottom of the beam ends from secondary corrosion.

Effect of the morphology of long-period stacking ordered phase on mechanical properties and corrosion behavior of cast Mg-Zn-Y-Ti alloy

In this study, three different morphologies of long-period stacking ordered (LPSO) phase, i.e. lamellar, block-like, and rod-like, were obtained through various heat treatment processes. The effect of the morphology of LPSO phase on mechanical properties and corrosion behavior of cast Mg-Zn-Y-Ti alloy was investigated accordingly. The results suggested that the block-like LPSO phases in the as-cast alloy transformed into the rod-like LPSO phases during heat treatment at high temperature, while the low temperature was conducive to the precipitation of lamellar phases in the grain interior. The formation of the rod-like LPSO phases resulted in an increase of 42% in elongation while maintaining a high tensile strength. In addition, the alloys with the rod-like LPSO phases exhibited more uniform corrosion mode and better corrosion resistance than the alloys with the block-like LPSO phases, so the former had excellent comprehensive properties. The precipitation of the lamellar LPSO phases not only reduced the mechanical properties, but also accelerated the corrosion rate and produced severe localized corrosion. Therefore, the mechanical properties and corrosion resistance of the alloys could be improved by regulating the morphology of LPSO phases.

A comparative study on corrosion and microstructure of direct metal laser sintered AlSi10Mg_200C and die cast A360.1 aluminum

Direct metal laser sintering (DMLS) is an additive manufacturing technique that creates near-net-shape functional components by selectively melting metal powders in two dimensions layer by layer using a high power laser as a heat source. This technique offers to create parts with complex net-shape structures at an affordable cost with the least lead time. The main purpose of this study is to investigate the corrosion behavior and microstructure of AlSi10Mg_200C manufactured using DMLS compared with its die cast counterpart (A360.1 die cast Al alloy). The impact of the alloy’s surface finish, i.e. as-printed surface versus as-ground one, on the corrosion performance was also investigated. Several AlSi10Mg_200C cube samples were additively manufactured through DMLS technique. In addition, the same size cubes were cut from an aluminum A360.1 die cast ingot. The corrosion behavior of the two alloys was analyzed utilizing potentiodynamic polarization testing and electrochemical impedance spectroscopy in aerated 3.5 wt.% NaCl solution to mimic sea water environment at 25 °C. Further, the microstructures and composition of the samples before and after corrosion testing were investigated using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) spectroscopy. The results confirmed that the corrosion resistance of the alloy processed through DMLS was significantly better than the cast counterpart. This was attributed to the fine microstructure produced by DMLS, uniform distribution of the fine Si particles without formation of any intermetallic, due to the extremely rapid cooling and solidification rate during DMLS process and slightly lower Fe and Cu concentration of the AlSi10Mg alloy. In contrast, the A360.1 cast Al alloy samples experienced severe localized corrosion of the Al matrix in the periphery of the Fe containing IMC and Si flakes. The results also highlighted improved corrosion resistance of the as-printed DMLS sample compared with that of the as-ground one.

On the severe localized corrosion susceptibility of the AA2198-T851 alloy

The time dependent susceptibility of AA2198-T851 Al-Cu-Li alloy to severe localized corrosion in 0.01 mol L−1 NaCl solution has been investigated by immersion and SVET tests. The results reveal that the propagation of severe localized corrosion, in the alloy, is crystallographic and it is associated with the slip bands in the individual grains of the alloy. The slip bands caused uneven precipitation of the active T1 particles. Also, oscillations in SVET current density values associated with deposition and detachment of corrosion products were observed. Furthermore, the intensity of corrosion activities increased over time for open or partially covered pits.

Corrosion behaviour of as-cast ZK40 with CaO and Y additions

Abstract The microstructures of as-cast ZK40, ZK40 with 2% (mass fraction) CaO and ZK40 with 1% (mass fraction) Y were investigated, and the intermetallic phase morphology and the distribution were characterised. By having discrete intermetallic particles at the grain boundaries for the ZK40, the microstructure was modified to a semi-continuous network of intermetallic compounds along the grain boundaries for the ZK40 with CaO or Y additions. The CaO was not found in the microstructure. However, Ca was present in Ca2Mg6Zn3 intermetallic compounds which were formed during casting. Hydrogen evolution and electrochemical impedance spectroscopy tests revealed that the addition of CaO slightly enhanced the corrosion resistance whereas Y had a negative effect on the corrosion resistance of ZK40. Immersion tests showed that severe localised corrosion as well as corrosion along the intermetallic compounds played an important role in the corrosion process of ZK40–Y whereas the localised corrosion was not pronounced for ZK40 or ZK40–CaO alloys. Micro-segregation in the α-Mg matrix was notably higher for the ZK40 alloy compared with the modified alloys. The combination of this effect with a possible formation of a more stable corrosion layer for the ZK40–CaO was attributed as the main reason for an improved corrosion resistance for the ZK40–CaO alloy.

Corrosion of low alloy steel containing 0.5% chromium in supercritical CO2-saturated brine and water-saturated supercritical CO2 environments

The corrosion behavior of P110 low-Cr alloy steel in supercritical CO2-saturated brine (aqueous phase) and water-saturated supercritical CO2 (SC CO2 phase) was investigated. The results show that P110 steel primarily suffered general corrosion in the aqueous phase, while severe localized corrosion occurred in the SC CO2 phase. The formation of corrosion product scale on P110 steel in the aqueous phase divided into three stages: formation of the initial corrosion layer containing amorphous Cr(OH)3, FeCO3 and a small amount of Fe3C; transformation of initial corrosion layer to mixed layer, which consisted of FeCO3 and a small amount of Cr(OH)3 and Fe3C; growth and dissolution of the mixed layer. Finally, only a single mixed layer covered on the steel in the aqueous phase. However, the scale formed in SC CO2 phase consisted of two layers: the inner mixed layer and the dense outer FeCO3 crystalline layer.

Localized CO2 corrosion of carbon steel with different microstructures in brine solutions with an imidazoline-based inhibitor

CO2 corrosion behavior of carbon steel with different microstructures (H steel: coarse laminar pearlite; T steel: globular and shot rod shaped pearlite) was analyzed in 3 wt.% NaCl solution at 60 °C with imidazoline-based inhibitor by electrochemical and weight loss methods. Electrochemical measurements showed that, compared to H steel, the inhibitor film adsorbed on T steel had a higher pitting corrosion resistance and the inhibition efficiency for T steel was larger at each concentration of inhibitor. Weight loss results exhibited that both steels suffered general corrosion in absence of inhibitor; however, localized corrosion was observed on the samples with insufficient concentration of inhibitor. H steel suffered more severe localized corrosion than T steel, it was related to that H steel had a higher density of dislocations in the pearlite area and the larger driving force for galvanic corrosion. The localized corrosion on H steel mainly distributed on the laminar pearlite area.

On the AA2198-T851 alloy microstructure and its correlation with localized corrosion behaviour

The corrosion behaviour of AA2198-T851 alloy has been investigated using a combination of immersion tests and different microscopy techniques. Results showed that severe localized corrosion initiated within 1h of corrosion immersion test in 0.01molL−1 NaCl solution. The corrosion mechanism in this alloy is intragranular and it propagates crystallographically. The propagation occurs through grain orientation dependent bands and it can be likened to the movement of dislocation through slip planes. Corrosion rings around stable pits result from pH variations. Secondary pits form around primary pits within corrosion rings and are preceded by hydrogen evolution.

Analysis and Life Evaluation of CS2 Reaction Tube

The chemical composition analysis, macro and microstructure analysis, mechanical properties and other methods were used to analyze the state and life of CS2 reaction tube for a period of time. The results showed that there is no sulfur corrosion ditch in the furnace tube, and the other one has a uniform corrosion state except for the severe local corrosion. The mechanical properties are good at room temperature. The number and appearance of phase are the main reason for making material brittle, welding property degradation and causing crack. The approximate residual life of the furnace tube is also evaluated by various means analysis and life calculation. It is recommended that the tube be replaced with a higher grade nickel-chromium alloy instead of HK40.

Enhancement of pure titanium localized corrosion resistance by anodic oxidation

The corrosion behavior of commercially pure titanium (UNS R50400, ASTM grade 2) was investigated in presence of aggressive, bromides containing, species, reported to cause severe localized corrosion compared to chlorides. To enhance localized corrosion resistance of the metal, several surface treatments were performed. Samples anodized at potentials between 10 and 200 V were characterized in term of oxide thickness and morphology and tested with potentiodynamic analyses in ammonium bromide solution. Base metal was prepared both with etching and mechanical polishing pre‐treatment, to enlighten the effect of pre‐treatment sample preparation on post‐treatment corrosion resistance.

Alloying effect of copper concentration on the localized corrosion of aluminum alloy for heat exchanger tube

This study examined the alloying effect of Cu content on the localized corrosion properties of Al alloy in synthetic acid rain containing 200 ppm of Cl- ion. In aluminum alloy tubes, a small amount of Cu is contained as the additive to improve the mechanical strength or as the impurity. The Cu-containing intermetallic compound, Al2Cu can cause galvanic corrosion because it has more noble potential than Al matrix. Therefore aluminum tube could be penetrated by localized corrosion attack. The results were obtained from electrochemical test, scanning electron microscopy, and time of flight secondary ion mass spectrometry (ToF-SIMS) mapping. Severe localized corrosion was occurred on the Al-0.03 wt% Cu alloy. The negative effect of Cu on the pitting corrosion was attributed to the presence of the Al2Cu precipitates.

Long-term under-deposit pitting corrosion of carbon steel pipes

Some steel water injection pipelines used to increase the yield from oil production reservoirs in the offshore oil industry have experienced severe channelling corrosion at the 6 o′clock position. The examination of field observations suggests both under-deposit corrosion (UDC) and microbiologically influenced corrosion (MIC) are likely to be associated with the phenomenon. Long-term laboratory experiments are described to distinguish the relative contributions of the presence of deposits, MIC and nitrate addition to the formation of channelling corrosion. Half-pipe steel specimens were exposed to different simulated test environments up to 365 days. The analysis of pitting morphology and pitting depth shows the synergistic effect of MIC and under-deposit corrosion led to severe localized corrosion. Nitrate addition caused most severe localized corrosion. Extreme value distribution examination shows Gumbel function is not appropriate to describe all the pit depth data for 1 year exposure. The results have implications for the corrosion management in industrial practice.

Erosion-corrosion characteristics of spark plasma sintered pure nickel in simulated mine water

This study estimates the impact of shear stress and solid particles on the erosion-corrosion behaviour of spark plasma sintered pure nickel in simulated mine water. Rotating cylinder electrode system was employed to carry out the erosion-corrosion tests by weight-loss and electrochemical measurements. Corroded coupons were examined with the aid of microscope to assess the surface morphology. The gravimetry data was inconsistent with both weight gain and weight loss recorded. The impact of the hydrodynamic parameters was correlated with the pitting resistance and re-passivation behaviour of the sintered nickel, while the morphology results showed minimal general attack and severe localised corrosion.

Long-term durability of reinforced concrete piles from the Hornibrook Highway Bridge

After more than 75 years continuous exposure to the Pacific Ocean waters on the Queensland coast, the 879 reinforced concrete driven piles that supported the superstructure of the Hornibrook Highway Bridge appeared to be in remarkably good condition when the bridge was demolished during 2011–2012. Detailed investigations revealed excellent, very hard concrete with pH values still around 12 and very little evidence of serious corrosion of the steel reinforcement. The concrete chloride content at the reinforcement was considerably more than the usually accepted limits. However, a few isolated occurrences of very severe localised reinforcement corrosion were found during demolition even though there was little visual external evidence. Possible reasons for the various observations are discussed, together with the practical implications.

Electrochemical and in vitro bioactivity of nanocomposite gelatin-forsterite coatings on AISI 316 L stainless steel

Abstract AISI 316L stainless steel has been widely considered as implant materials in biomedical applications owing to its low cost and superior strength. However, its weak corrosion resistance due to the release of nickel, chromate and molybdenum ions as well as its inert nature limits its clinical application specifically long-standing performances. The aim of this study was to prepare and characterize gelatin-forsterite (Mg2SiO4) nanocomposite coatings consisting of various amounts of forsterite nanopowder (0, 1, 2.5 and 5 wt.%) on AISI 316L substrate in order to improve simultaneously corrosion resistance and in vitro bioactivity. Nanocomposite gelatin-forsterite coatings were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. Furthermore, the bioactivity of gelatin-forsterite coated specimens were evaluated via soaking in simulated body fluid (SBF) for 28 days at 37 °C. Results demonstrated the formation of crack-free and homogeneous coatings without any observable defect and pore. The surface roughness and adhesion strength of the coatings enhanced with increasing forsterite content. Moreover, the corrosion evaluation considered by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) demonstrated that compered to unmodified AISI 316L substrate, the corrosion resistance of gelatin-forsterite nanocomposite-coated substrates significantly improved. Moreover, nanocomposite coatings were able to persist severe localized corrosion in physiological solution indicating their long-term biostability. Moreover, the formation of bone-like apatite layer on the nanocomposite-coated samples was observed in SBF, which might be helpful to integrate with host tissue. Overall, it is anticipated that the novel proposed nanocomposite coatings of gelatin-forsterite might be potentially useful for orthopedic implants.

Corrosion and bioactivity evaluation of nanocomposite PCL-forsterite coating applied on 316L stainless steel

Abstract The weak corrosion resistance is the main drawback of 316L stainless steel (316 LSS) as implant materials for biomedical applications. Therefore, surface modification of 316 LSS with various coating techniques, which could simultaneously improve the corrosion resistance, biocompatibility and bioactivity is necessary. The present study was aimed to design a novel nanocomposite poly(e-caprolactone) (PCL)-forsterite (Mg2SiO4) coating on 316 LSS using dip-coating technique to improve bioactivity and corrosion resistance. Furthermore, the effects of various concentrations of forsterite nanopowder (0, 1, 2.5 and 5 wt.%) on the morphology, contact angle, roughness, in vitro bioactivity and corrosion resistance were investigated. Results confirmed the successful formation of crack-free nanocomposite coating on 316 LSS. Moreover, in vitro bioactivity of the nanocomposite coatings demonstrated enhanced Ca-P precipitation on the surface of samples with increasing forsterite content. The corrosion evaluation considered by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) demonstrated that while PCL and PCL-forsterite nanocomposites coatings showed improved corrosion resistance compared to 316 LSS, nanocomposite coatings consisting of 1 wt.% forsterite nanopowder exhibited superior resistance to corrosion attack than pristine PCL, and were able to survive severe localized corrosion in physiological solution. It is envisioned that the proposed nanocomposite can be useful for orthopedic applications in the future.

Recommend design of filler metal to minimize carbon steel weld metal preferential corrosion in CO2-saturated oilfield produced water

The paper proposes a recommend design for the alloying elements in the filler metal to minimize preferential weld corrosion of carbon steel. The tensile and corrosion resistance properties of the weld metal are considerably improved by using a filler metal containing alloying elements according to the recommended design. Analysis of the morphology and composition of corrosion products on weld metals showed that the common weld metal suffered severe localized corrosion, whereas the weld metal with the alloying elements exhibited uniform corrosion. Based on these results, a tentative mechanism of CO2 corrosion resistance for both weld metals has been proposed.

Corrosion of low alloy steel and stainless steel in supercritical CO2/H2O/H2S systems

The corrosion of low alloy steel and stainless steel in the dynamic supercritical CO2/H2O/H2S system was studied. A Cr-containing scale, mainly consisted of FeCO3, Cr(OH)3 and iron sulfide (mackinawite), formed on low alloy steel. FeCO3 formed via the solid state reaction and precipitation reaction, while mackinawite could only form via the solid state reaction. In the aqueous phase, low alloy steel suffered severe general and localized corrosion, but 316L stainless steel suffered pitting corrosion. In the supercritical CO2 phase, localized corrosion was dominant for low alloy steel, and 316L stainless steel was highly resistant to corrosion.

Influence of thermomechanical treatments on localized corrosion susceptibility and propagation mechanism of AA2099 Al–Li alloy

In order to manifest the influence of specific microstructural component on the development of severe localized corrosion in an AA2099 aluminum–lithium alloy, the corrosion behavior of the alloy subjected to solution heat treatment, cold working and artificial ageing was investigated. Immersion testing and potentiodynamic polarization were employed to introduce localized corrosion; scanning electron microscopy and transmission electron microscopy were used to characterize the alloy microstructure and corrosion morphology. It was found that the susceptibility of the alloy to severe localized corrosion was sensitive to thermomechanical treatments. Additionally, the state of alloying elements influenced the mechanism of localized corrosion propagation. Specifically, the alloy in T8 conditions showed higher susceptibility to severe localized corrosion than that in other conditions. During potentiodynamic polarization, the alloy in solution heat-treated and T3 conditions displayed crystallographic corrosion morphology while the alloy in T6 and T8 conditions exhibited selective attack of grain interiors and grain boundaries in local regions.

Steel Corrosion in Submerged Concrete Structures—Part 2: Modeling of Corrosion Evolution and Control

A predictive model that simulates the sequence of events leading to the development of a stable corrosion distribution pattern in the submerged zone of a reinforced concrete column in a marine environment is described. The model incorporates potential dependent threshold (PDT) features that update the corrosion projection as additional parts of the system begin to actively corrode. Results are consistent with field observations reported in Part 1 and supported the interpretation that the passive state of a large portion of the steel can be preserved in the presence of high chloride concentration at rebar depth, even if typically assumed chloride threshold values were exceeded. In contrast, severe localized corrosion may take place elsewhere in the submerged region despite limited oxygen availability there. The calculations indicated that high concrete resistivity, which is typical in low-permeability concrete chosen for achieving long service life in the above water region, may under some circumstances pr...