Atmospheric corrosion of carbon steel: Results of one-year exposure in an andean tropical atmosphere in Colombia

In this study was examined the response of carbon steel to atmospheric corrosion after one-year exposure in Valle de Aburrá, a subregion located in northwestern Colombia. The study involved the assessment of material mass loss and corrosion rate, the characterization of atmospheric aggressiveness, and the analysis of the morphology and composition of corrosion products in five different sites. Climatological and meteorological factors were assessed by testing for chloride content, sulfur dioxide levels, and time of wetness (TOW). The analysis of corrosion products was conducted using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. Based on corrosion rates, two sites exhibited a more aggressive environment, with a corrosivity category of C3, while the remaining sites were categorized as C2. The study confirmed the presence of lepidocrocite and goethite phases on the surface of carbon steel at all test sites. Data analysis revealed that both the TOW and the industrial activity significantly influence the corrosion of this metal.

Modelling of corrosion rate in the drinking water distribution network using Design Expert 13 software

This study is focused on the modelling of the composite effect of corrosion factors using Design Expert 13 software on the corrosion rate in the water distribution network of Patna (Bihar), India. A total of nine variables, including pH, temperature, total dissolved solid (TDS), alkalinity, calcium hardness, chloride, sulphate, dissolved oxygen (DO) and time, were considered for modelling. The physicochemical parameters were determined through regular monitoring of water samples. The corrosion rate was determined by the direct monitoring of water distribution pipes using adjustments of seven GI coupons for 45, 90, 135, 180, 225, 270 and 315 days. Modelling was performed for various corrosion factors using the low-level and high-level experimental ranges. Nine of the corrosion factors, i.e. pH, temperature, TDS, alkalinity, calcium hardness, chloride, sulphate, DO and time, were considered in this study. The data used for low-level and high-level range were 7.28, 23, 430, 115, 24, 18, 10.94, 3.5 and 0 and 7.86, 28, 704, 284, 180, 98, 38.7, 6.8 and 315, respectively. Using the Box-Behnken design (BBD), 160 runs were conducted, including ten replicates at the central point of each block. The results of ANOVA indicate that the values of R², adjusted R² and predicted R² are 0.9714, 0.9507 and 0.8941, respectively. The value of R² (0.9714) was close to 1, which indicates a good fit. The adequate precision was found to be 30.8442, indicating a good signal. The coefficient of variance discusses reproducibility, and in this case, it was 9.90%. On the basis of the ANOVA result, the quadratic model is well-fitted and can be accepted as a suitable model. A total of seven parameters, such as chloride, sulphate, hardness, alkalinity, pH, calcium and hardness, were used for the design of the experimental corrosion rate (CR). Corrosion rate as observed by direct monitoring of the water distribution system was 1.37, 3.08, 1.90, 1.38, 1.09, 2.05 and 1.45 MPY for 45, 90, 135, 180, 225, 270 and 315 days, respectively. These individual CR versus synthetic aqueous solutions were used to validate the interaction of the response surface. It was observed that the trend of individual corrosion rates in synthetic aqueous solutions and the interaction of composite variables with corrosion rates in a quadratic model of response surfaces were clearly correlated.

Effect of Pseudomonas aeruginosa on corrosion of X65 pipeline steel

Microbiologically influenced corrosion (MIC) has caused great losses to many industries. This paper aimed to study the corrosion behavior of P. aeruginosa on X65 steel. The corrosion behavior of P. aeruginosa on X65 steel under aerobic and anaerobic conditions was studied by scanning electron microscopy, energy dispersive spectrometer and electrochemical analysis techniques. The results showed that the corrosion rate of X65 steel in bacterial environment is higher than that in sterile environment. In anaerobic environment, the corrosion of P. aeruginosa is mainly secreted acidic metabolites, and alkaline substances are corroded in aerobic environment. In general, the corrosion of X65 steel by P. aeruginosa in aerobic environment is more serious than that in anaerobic environment.

Microstructural, mechanical, and electrochemical analysis of carbon doped AISI carbon steels

The effect of carbon doping contents on the microstructure, hardness, and corrosion properties of heat-treated AISI steel grades of plain carbon steel was investigated in this study. Various microstructures including coarse ferrite-pearlite, fine ferrite-pearlite, martensite, and bainite were developed by different heat treatments i.e. annealing, normalizing, quenching, and austempering, respectively. The developed microstructures, micro-hardness, and corrosion properties were investigated by a light optical microscope, scanning electron microscope, electromechanical (Vickers Hardness tester), and electrochemical (Gamry Potentiostat) equipment, respectively. The highest corrosion rates were observed in bainitic microstructures (2.68-12.12 mpy), whereas the lowest were found in the fine ferritic-pearlitic microstructures (1.57-6.36 mpy). A direct correlation has been observed between carbon concentration and corrosion rate, i.e. carbon content resulted in an increase in corrosion rate (2.37 mpy for AISI 1020 to 9.67 mpy for AISI 1050 in annealed condition).

Laser machined micropatterns as corrosion protection of both hydrophobic and hydrophilic magnesium

Magnesium and its alloys are promising candidate materials for medical implants because they possess excellent biocompatibility and mechanical properties comparable to bone. Furthermore, secondary surgical operations for removal could be eliminated due to magnesium's biodegradability. However, magnesium's degradation rate in aqueous environments is too high for most applications. It has been reported that hydrophobic textured surfaces can trap a surface gas layer which acts as a protective barrier against corrosion. However, prior studies have not investigated separately the role of the texture and hydrophobic treatments on magnesium corrosion rates. In this study, pillar-shaped microstructure patterns were fabricated on polished high purity magnesium surfaces by ablation with a picosecond laser. Some micropatterned samples were further processed by stearic acid modification (SAM). Micropatterned surfaces with SAM had hydrophobic properties with water droplet contact angles greater than 130°, while the micropatterned surfaces without SAM remained hydrophilic. The corrosion properties of textured and smooth magnesium surfaces in saline solution were investigated using electrochemical impedance spectroscopy (EIS) and optical microscopy. Corrosion rates on both hydrophobic and hydrophilic laser machined surfaces were reduced ∼90% relative to polished surfaces. Surprisingly, corrosion rates were similar for both hydrophobic and hydrophilic surfaces. Indirect evidence of local alkalization near microstructures was found and was hypothesized to stabilize the Mg(OH)₂ layer, thereby inhibiting corrosion on hydrophilic surfaces. This is different than the corrosion resistance mechanism for superhydrophobic surfaces which makes use of gas adhesion at the liquid solid interface. These results suggest additional processing to render the magnesium hydrophobic is not necessary since it does not significantly enhance the corrosion resistance beyond what is conferred by micropatterned textures.

Limiting nitrate triggered increased EPS film but decreased biocorrosion of copper induced by Pseudomonas aeruginosa

Biocorrosion of Cu remains a significant challenge in marine engineering but the mechanism is still not clear. The nutrients in marine environment affect the microbe's growth and the formation of biofilm, and then affect biocorrosion of metal to a large extent. In this study, the effect of NO₃^- concentration in Pseudomonas aeruginosa (P. aeruginosa) medium on the formation of extracellular polymer substance (EPS) film and biocorrosion of Cu were studied. The experiments results showed that limiting NO₃^- in culture medium triggered increased EPS film but decreased biocorrosion of Cu induced by P. aeruginosa. With increase of NO₃^- content in the culture medium, the Cu surface attached less polysaccharides and proteins, but the Cu corrosion rate was accelerated. The weight loss of Cu and the maximum pit depth were both increased with increase of NO₃^- content. The XPS and XRD analyses indicated that the major corrosion product is Cu₂O. The increased corrosion rate with increase of the NO₃^- level were attributed to the EET-MIC route, the formation of Cu(NH₃)₂⁺, and the more loose EPS film.

The empirical prediction of weight change and corrosion rate of low-carbon steel

Understanding the corrosion rate of metallic building materials is very important to maximize their beneficial use of public facilities. Direct measurements of the weight change and corrosion rate would be time consuming and expensive. This study aims to develop new empirical models based on the experimental data of testing 25 specimens immersed in five different environments for predicting the weight change and corrosion rate of the low-carbon steel. Using the equation developed based on the correlation between corrosion rate and chloride ion concentration is able to predict the corrosion rate of low-carbon steel at the limited chloride ion concentration. An increase in the trend lines of plotting the modeled and measured weight change of low-carbon steel versus immersion time is very similar to each other and progressively increase with increasing of the NaCl concentration. The corrosion rate of low-carbon steel increases from 0.202 to 0.286 mm/y with increasing of the NaCl concentration from 0 to 5% (w/w) in aqueous solution. The weight change and corrosion rate of the steel material are predicted using the new empirical models to contribute to the most reliable applications of low-carbon steel building materials in the future.

Green corrosion inhibition and adsorption characteristics of Luffa cylindrica leaf extract on mild steel in hydrochloric acid environment

The corrosion inhibition of Luffa cylindrica Leaf Extract (LCLE) was investigated using gravimetric, depth of attack and surface analysis techniques. Effect of inhibitor concentrations (0.50-1.00 g/l), temperatures (30-60 °C) and immersion time (4-12 h) was studied on the Inhibition Efficiency (IE) of the extract on Mild Steel (MS) immersed in a 0.5 M HCl solution. The constituents of the proposed inhibitor were identified by using a GC-MS. The media solutions and adsorbed film on MS were characterized using FTIR Spectrophotometer. SEM microgram and surface tester were applied for studying surface morphology and depth of attack profile. The optimum IE of 87.89% was obtained. The LCLE adsorption on MS followed Langmuir isotherm and pseudo-second-order adsorption kinetics. Activation energy (28.71 kJ/mol), entropy (- 0.15 kJ/mol. K), average enthalpy (-28.00 kJ/mol) and Gibbs free energy (-11.43 kJ/mol) obtained at optimum condition indicate exothermic process and physical adsorption mechanism. The result obtained in this study compared well with many reported green inhibitors for MS corrosion.

Corrosion of Al2O3-Ti composites under inflammatory condition in simulated physiological solution

Alumina-titanium composites have shown good mechanical properties which makes them promising for orthopedic applications. The placement of an orthopedic implant involves an invasive procedure which stimulates a localized inflammatory response causing an acidic environment around the implant. This makes the study on corrosion more critical. Therefore, the aim of the present paper was to study the corrosion behavior of the composites with 75 vol% and 50 vol% Ti content (with alumina balance) fabricated by Spark Plasma Sintering under acidic condition representing inflammation and in two elapsed times (1 h and 1-day) using polarization and electrochemical impedance spectroscopy tests. For comparison, the experiments were also conducted in normal physiological solution after 1 h, and pure Ti (100vol%Ti) was fabricated by the same process and analyzed, similarly. Furthermore, behavior of the samples was studied after 48 days of immersion in the acidic and normal solutions using SEM, ATR-FTIR, AFM, and ICP-OES. The results of corrosion tests showed very good passivation behavior of 100vol%Ti and the composite containing 75vol.%Ti. The superiority of the 75vol.%Ti composite in corrosion characteristics in both solutions was also found. Its corrosion resistance was 20.3 MΩcm² under the inflammatory condition after 1-day, which was 39% higher than that of 100vol.%Ti under the same condition. The results of SEM indicated both corroded and mineral deposition zones on all materials' surfaces and the ATR-FTIR results revealed additional adsorbed bands related to water adsorption, OH and carbonate groups after immersion. The AFM analysis showed rougher morphology, particularly for 75 vol% Ti where the Rq was increased about 50 nm, and the ICP-OES results indicated 65.87% and 61.94% deposition of solution calcium on 75vol.%Ti and 50vol.%Ti, respectively. The acidic/inflammatory condition influenced the corrosion processes of all materials. Lower pH caused the passivation to occur sooner and the corrosion resistance to be higher.

Time-varying law of rebar corrosion rate in fly ash concrete

Whereas steel bar corrosion is the main cause for durability deterioration of existing reinforced concrete structures, it is important to understand the steel bar corrosion in concrete and predict the corrosion process in a sufficient way. In this paper, the corrosion process of rebar in ordinary concrete and three types of fly ash concrete specimens casted with 15%, 30% and 45% fly ash replacement ratios by mass under constant climate conditions were investigated. Meanwhile, the advanced digital video microscope measure system was used to study the microstructure of the steel/concrete interface at the different stages of corrosion. The effects of fly ash replacement were analyzed in terms of the electrical resistivity of concrete and the corrosion rate in the corrosion process of steel bars in fly ash concrete. The results showed that the resistivity of concrete increased with an increase in fly ash replacement, and the corrosion rate declined with the fly ash replacement increases. In addition, in fly ash concrete, the corrosion rate of plain bars were obviously smaller than that of ribbed bars.

Novel colour additive for bleach disinfectant wipes reduces corrosive damage on stainless steel

Bleach disinfectant wipes are corrosive to hospital surfaces and equipment. This study measured the effect of two widely used bleach wipes, with and without Highlight^® colour additive, on stainless steel to quantify the rate of corrosion and to determine the effect of Highlight^® on reducing surface damage caused by bleach wipes. The two bleach wipes alone caused severe corrosion [>5 mils per year (mpy), where 1 mil = 0.001 inch], while the addition of Highlight^® reduced the rate of corrosion significantly (<2 mpy) and prevented discolouration of the metal. These results indicate that Highlight^® reduces the deleterious corrosive effects of bleach wipes, thus improving their viability for cleaning healthcare surfaces.

Use of carbon steel ball bearings to determine the effect of biocides and corrosion inhibitors on microbiologically influenced corrosion under flow conditions

A consortium of sulfate-reducing bacteria consisting mostly of Desulfovibrio, Desulfomicrobium, and Desulfocurvus from oil field produced water was cultivated in a chemostat, receiving medium with 20 mM formate and 10 mM sulfate as the energy and 1 mM acetate as the carbon source. The chemostat effluent, containing 5 mM sulfide and 0.5 mM of residual acetate, was passed through 1-ml syringe columns with 60 carbon steel ball bearings (BBs) of 53.6 ± 0.1 mg each at a flow rate of 0.8 ml/h per column. These were treated every 5 days with 1.6 ml of 300 ppm of glutaraldehyde (Glut), tetrakis(hydroxymethyl)phosphonium sulfate (THPS), benzalkonium chloride (BAC), or Glut/BAC, a mixture of Glut and BAC. Alternatively, BBs were treated with 33% (v/v) of a water-soluble (CR_W) or an oil-soluble (CR_O1 or CR_O3) corrosion inhibitor for 20 s after which the corrosion inhibitor was drained off and BBs were packed into columns. The effluent of untreated control columns had no acetate. Treatment with the chemically reactive biocides Glut and THPS, as well as with Glut/BAC, gave a transient increase of acetate indicating decreased microbial activity. This was not seen with BAC alone indicating it to be the least effective biocide. Relative to untreated BBs (100%), those treated periodically with Glut, THPS, BAC, or Glut/BAC had a general weight loss corrosion rate of 91, 81, 45, and 36% of the untreated rate of 0.104 ± 0.004 mm/year, respectively. Single treatment with corrosion inhibitors decreased corrosion to 48, 2, and 1% of the untreated rate for CR_W, CR_O1 and CR_O3, respectively. Analysis of the distribution of corrosion rates from the weight loss of individual BBs (N = 120) indicated the presence of a more slowly and a more rapidly corroding group. BAC treatment prevented emergence of the latter, and this quaternary ammonium detergent appeared most effective in decreasing corrosion not because of its biocidal properties, but because of its corrosion inhibitory properties.

Effect of solution pH on aging dynamics and surface structural evolution of mZVI particles: H2 production and spectroscopic/microscopic evidence

A microscale zero-valent iron (mZVI)-based in situ reactive zone is a promising technology for contaminated groundwater remediation. Estimation of mZVI aging behavior after its injection into the subsurface is essential for efficiency and longevity assessments. In this study, batch tests were conducted to investigate the effect of initial pH on mZVI aging dynamics, as well as the formation and evolution of aging products over 112 days. Results indicated that mZVI aging accelerated with decreasing initial pH. Corrosion rates of mZVI particles under pH 6.0 and 7.5 were approximately two orders of magnitude higher than those observed at pH 9.0. The morphological, structural, and compositional evolution of mZVI particles in three systems (pH = 6.0, 7.5, and 9.0) were investigated using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. In acidic and neutral solutions, a thick passivation layer with loosely and unevenly distributed aging precipitates was observed, and Fe₃O₄ was the final aging precipitate. Nevertheless, in alkaline solutions, minute aging precipitates were detected on the mZVI surface at 112 day. Characterization results suggested that mZVI was oxidized via the Fe⁰-Fe(OH)₂-Fe₃O₄ route. These findings shed new light on mZVI aging mechanisms, particularly its physicochemical characteristics and the structural evolution of mZVI in field-scale groundwater remediation applications.

A rapid, non-destructive methodology to monitor activity of sulfide-induced corrosion of concrete based on H2S uptake rate

Many existing methods to monitor the corrosion of concrete in sewers are either very slow or destructive measurements. To overcome these limitations, a rapid, non-invasive methodology was developed to monitor the sulfide-induced corrosion process on concrete through the measurement of the H2S uptake rates of concrete at various corrosion stages. The H2S uptake rate for a concrete coupon was determined by measuring the gaseous H2S concentrations over time in a temperature- and humidity-controlled gas-tight reactor. The reliability of this method was evaluated by carrying out repeated tests on different concrete coupons previously exposed to 50 ppm of H2S, at 30 °C and 100% relative humidity for over 32 months. The H2S uptake measurements showed good reproducibility. It was also shown that a severely corroded coupon exhibited higher sulfide uptake rates than a less corroded coupon. This could be explained by the corrosion layer in the more corroded coupon having a higher biological sulfide oxidation activity than the less corroded coupon. Additionally, temperature changes had a stronger effect on the uptake rate of the heavily corroded coupon compared to the less corroded coupon. A corrosion rate of 8.9 ± 0.5 mm/year, estimated from the H2S uptake results, agreed well with the corrosion rate observed in real sewers under similar conditions. The method could be applied to investigate important factors affecting sulfide-induced concrete corrosion, particularly temperature, fluctuating gaseous H2S concentrations, oxygen concentrations, surface pH and relative humidity.