Major Corrosion Research Articles

Carbon steel corrosion in clay-rich environment

We investigated the carbon steel corrosion in carbon dioxide clay-rich environment to understand its behavior under geological conditions. The results show the formation of magnetite as the main corrosion product in the first step of the corrosion process, followed by the formation of different corrosion products with complex mixtures of iron-oxide, hydroxycarbonate, hydroxychloride and sulfide phases. These results strongly contrast with similar experiments conducted under H2 atmosphere where the major corrosion products consisted of iron sulfides. It appears then important to consider all the geochemical parameters including gas composition to better study corrosion of steel buried in geological formations.

Corrosion of novel Pb–Mg–Al–B nuclear shielding alloy in fluoride medium

Five kinds of Pb–Mg–Al–B alloys with B atomic fraction of 0, 1·84, 3·62, 5·36 and 7·06% were prepared by induction melting. The corrosion behaviour of Pb–Mg–Al–B in 3·5 wt-%NaF solution was investigated by immersion tests, neutral salt spray and electrochemical measurements. The surface morphology and corrosion products of alloys were measured using scanning electron microscopy (SEM), X-ray diffraction and X-ray photoelectron spectroscopy. Results show that the Pb–Mg–Al–B alloy with 5·36%B shows the best corrosion resistance; the volume fraction and distribution of Mg2Pb, Mg17Al12 and other phases affect the corrosion resistance significantly; the major corrosion products are Mg17Al12, Pb, PbO, Al2O3, etc., and Mg is apt to form a microgalvanic cell with Mg2Pb (Mg2Pb–Mg) in corrosive solution, and a bit of product of MgF2 film has a role to protect alloys; and the different corrosion resistances are caused by the different microstructure of alloys with different B additions.

Intertek signs major corrosion monitoring contract

Intertek signs major corrosion monitoring contract

Hot Corrosion of T22, T23, and T91 Steels in Na2SO4 Salts at 800 and 900 ℃

Ferritic T22, T23, and T91 steels were corroded in Na2SO4 salt at 800 and 900 ℃, and their hot corrosion behavior was studied. The corrosion resistance increased in the order of T22, T23, and T91. The good corrosion resistance of T91 at 800 ℃ was mainly attributed to Cr, which led to the formation of thin scales. By contrast, the amount of Cr in T22 and T23 was not enough to form protective scales so that thick, porous, bi-layered scales formed on T22 and T23 at 800 ℃. Nonetheless, T22, T23, and T91 suffered rapid scaling and dissolution of scales into the salt at 900 ℃. Iron oxides were the major corrosion products in this study.

The role of iron in sulfide induced corrosion of sewer concrete

The sulfide-induced corrosion of concrete sewer is a widespread and expensive problem for water utilities worldwide. Fundamental knowledge of the initiation and propagation of sewer corrosion, especially the interactions between chemical reactions and physical structure changes, is still largely unknown. Advanced mineral analytical techniques were applied to identify the distribution of corrosion products and the micro-cracking that developed along the corrosion boundary. It was found that sewer concrete corrosion caused by reactions with sulfuric acid progressed uniformly in the cement of concrete. In contrast to conventional knowledge, iron rust rather than gypsum and ettringite was likely the factor responsible for cracking ahead of the corrosion front. The analysis also allowed quantitative determination of the major corrosion products, i.e., gypsum and ettringite, with the latter found closer to the corrosion front. The conceptual model based on these findings clearly demonstrated the complex interactions among different chemical reactions, diffusion, and micro-structure changes.

The corrosion behaviors of Mg–7Gd–5Y–1Nd–0.5Zr alloy under (NH4)2SO4, NaCl and Ca(NO3)2 salts spray condition

The corrosion behaviors of Mg–7Gd–5Y–1Nd–0.5Zr alloys after T5 treatment under (NH 4 ) 2 SO 4 , NaCl and Ca(NO 3 ) 2 salt spray condition were investigated by weight loss rates, residual mechanical properties, scanning electron microscope (SEM), X-ray Diffraction (XRD) and potentiodynamic polarization tests. The corrosion degree of Mg–7Gd–5Y–1Nd–0.5Zr alloys in Ca(NO 3 ) 2 salt spray was very shallow by corrosion morphology and the corrosion route was extended along the surface in texture-like shape, while the alloy in NaCl and (NH 4 ) 2 SO 4 salt spray were major local corrosion and there were serious corrosion pits on the surface. The weight loss rates in (NH 4 ) 2 SO 4 , NaCl and Ca(NO 3 ) 2 salt spray was respectively 0.4147, 0.1618 and 0.0725 mg/(cm 2 d −1 ). The results of residual mechanical properties indicated that the corrosion order in salts spray of Mg–7Gd–5Y–1Nd–0.5Zr alloys is NH 4 SO 4 > NaCl > Ca(NO 3 ) 2 , which was consistent with the results of potentiodynamic polarization tests. The type of the salts will play a vital role in the initiation of the corrosion of EW75 alloy when they are used in the atmosphere environments. Inorganic salts with the smaller PH value after dissolution will have a stronger impact on the corrosion of EW75 magnesium alloys.

Optimising the Design of Fe0-Based Filtration Systems for Water Treatment: The Suitability of Porous Iron Composites

This study assessed the functionality of metallic iron (Fe0) filtration systems using porous iron composite (PIC) as an alternative to granular Fe0/aggregate mixtures. The usage of PIC for water treatment has many challenges which are related to the well-drained nature of highly porous filters and the corresponding increase in hydraulic conductivity (shorter contact time). In this article, the extent of (i) iron exhaustion and (ii) porosity loss in four filtration systems are critically discussed. The considered filtration systems are: (i) Fe0 alone, (ii) PIC alone, (iii) Fe0/sand and (iv) Fe0/pumice. In all four systems, mono-sized granular spherical particles are assumed. Sand and Fe0 are compact (f = 0 %) whereas PIC and pumice are porous (e.g. f = 40 %). Results demonstrated that under anoxic conditions (Fe3O4 as major corrosion products) Fe0 depletion is possible in all systems except Fe0 alone. Under oxic conditions (e.g. formation of Fe(OH)3), the PIC system exhibited the highest level of Fe0 depletion (58 %). The increasing order of sustainability was: Fe0 < Fe0/sand < Fe0/PM < PIC. These results suggested that manufacturing PIC with defined porosity and intrinsic reactivity is the key for more efficient usage of Fe0 for environmental remediation and water treatment.

Tracking the corrosion of magnesium sand cast AM50 alloy in chloride environments

An experimental procedure for tracking corrosion on lightweight alloys has been developed using a combination of microscopy and corrosion studies using commercial sand cast magnesium AM50 alloys. Corrosion penetration depths were measured and characterized with CLSM and SEM/XEDS, respectively. Corrosion depths on α-grains in the alloys were expressed as a function of their Al content. Al-rich β-phases and eutectic α-phase microstructures were observed to be most corrosion resistant due to an enrichment of Al, identified with TEM, near the oxide/alloy interface. Sand cast alloys were found to be susceptible to major corrosion events in regions with depleted Al content.

Corrosion of Austenitic Steels and Their Components in Vanadium-Containing Chloride Melts

Corrosion behavior of stainless steel types AISI 316L, 316Ti and 321 and their components (iron, chromium, nickel and molybdenum) was studied at 750 0C in NaCl-KCl-VCl2 melts. It was found that iron, chromium and manganese species constitute the major corrosion products of austenitic steels and Fe2+, Cr2+, Ni2+, and Mo3+ ions are formed as a result of interaction of corresponded metal and vanadium-containing chloride melts. It was found that austenitic stainless steels are subjected to high temperature sensitization and this phenomenon determines the intergranular character of steel corrosion. Presence of vanadium ions in electrolyte leads to intensification of corrosion processes due to increased oxidation of electronegative steel components and alloy formation. Metallic molybdenum has highest corrosion resistance among studied construction materials.

Materials challenges in nuclear energy

Nuclear power currently provides about 13% of electrical power worldwide, and has emerged as a reliable baseload source of electricity. A number of materials challenges must be successfully resolved for nuclear energy to continue to make further improvements in reliability, safety and economics. The operating environment for materials in current and proposed future nuclear energy systems is summarized, along with a description of materials used for the main operating components. Materials challenges associated with power uprates and extensions of the operating lifetimes of reactors are described. The three major materials challenges for the current and next generation of water-cooled fission reactors are centered on two structural materials aging degradation issues (corrosion and stress corrosion cracking of structural materials and neutron-induced embrittlement of reactor pressure vessels), along with improved fuel system reliability and accident tolerance issues. The major corrosion and stress corrosion cracking degradation mechanisms for light-water reactors are reviewed. The materials degradation issues for the Zr alloy-clad UO2 fuel system currently utilized in the majority of commercial nuclear power plants are discussed for normal and off-normal operating conditions. Looking to proposed future (Generation IV) fission and fusion energy systems, there are five key bulk radiation degradation effects (low temperature radiation hardening and embrittlement; radiation-induced and -modified solute segregation and phase stability; irradiation creep; void swelling; and high-temperature helium embrittlement) and a multitude of corrosion and stress corrosion cracking effects (including irradiation-assisted phenomena) that can have a major impact on the performance of structural materials.

Treatment of Acidic Petroleum Crude Oil Utilizing Catalytic Neutralization Technique of Magnesium Oxide Catalyst

The presence of naphthenic acids in crude oils has caused a major corrosion problem to the production equipment, storage and transport facilities in the petroleum industry. The level of acidity of crude oil was determined by the value of Total Acid Number (TAN) in the oil samples. Two types of crude: Petronas Penapisan Melaka Heavy Crude and Petronas Penapisan Melaka Light Crude were studied. Various parameters studied were the amount of chemical dosing, type of catalyst, different catalyst calcination temperatures, and catalyst ratio of basic metal and dopant. The basic chemical used was ammonia solution in ethylene glycol (NH3-EG) with a concentration range of 100-1000 mg/L. The best experimental condition for the possible TAN for the two samples is 1000 mg/L of NH3-EG, and the catalyst reaction must be in the range of 35-40°C. Cu/Mg (10:90)/Al2O3 catalyst successfully reduced TAN in Heavy Crude for about 84.8% while for Light Crude, TAN was reduced 66.7% with the aids of Ni/Mg (10:90)/Al2O3 catalyst. Increase concentration of basic chemical, reduced the total acid number value of both crude oil.

Forensic Engineering Investigation Of Dezincification In A Major Corrosion Litigation

Zinc-Rich Brasses With The Zinc Content Above 30% Can Be Involved In Corrosion Processes With Catastrophic Results. The Dezincification Results In A Low Strength Copper With A Porous Sponge Like Structure. The Case, Where Dezincification Occurred With Massive Impact, Involved 34,000 New Homes In An Urban Location In Nevada. These Homes Were Constructed Using Building Code Approved Plastic Pex Tubing For Plumbing With Brass Fittings. Leaks Developed In The Home Plumbing Systems After Approximately 3-6 Years. This Failure Resulted In Lawsuits Involving Home Owner Associations, Insurance Companies, Contractors, Plumbers, Architects, Manufacturers, And Suppliers.

Influence of dissolved inorganic carbon and calcium on gas formation and accumulation in iron permeable reactive barriers

Uncertainties in long-term reactivity and gas accumulation in Fe(0) permeable reactive barriers still hinder a broad application of this groundwater remediation technology. In this study long-term column experiments were conducted under varying geochemical conditions. Generation of hydrogen by anaerobic corrosion in Fe(0) reactive filters was mainly influenced by the mass flux of dissolved inorganic carbon. Both increased concentrations and volume flows led to a substantial rise in gas generation but only to slight differences of gas accumulation within the pores of the reactive filter. Comparisons of columns with different lengths showed higher averaged corrosion rates in the shorter and lower corrosion rates in the longer columns. Calcium in conjunction with dissolved inorganic carbon formed compact and localized aragonite minerals, while in the absence of calcium chukanovite dominated, which covered and passivated the reactive surface to a higher extent. Magnetite was the major crystalline corrosion product in the absence of carbonate and no decline in long term corrosion rates was observed within up to 700days of operation. Total gas yields of columns were restricted by passivation and approached a volume of approximately 13.5mL/g granulated cast iron.

Major corrosion factors in the CO 2 and H 2 S coexistent environment and the relative anti-corrosion method: Taking Tazhong I gas field, Tarim Basin, as an example

Abstract Anti-corrosion techniques are studied to deal with the CO 2 and H 2 S coexistent environment of the Tazhong I gas field. Orthogonal experiment with five different factors and levels is carried out to compare the influence of the factors on the corrosion rate of the sulfur-resistant tubing. These five factors are pressure of CO 2 , pressure of H 2 S, temperature, content of Cl − , and water cut. It is found that CO 2 pressure is the major corrosion factor. The combination of sulfur resistance tubing and corrosion inhibitor is selected as the anti-corrosion method and the proper corrosion inhibitor named YU-4 is designed according to the result of orthogonal experiment. This anti-corrosion method was used in 12 wells of the Tazhong I gas field, achieving good results. The average corrosion rate of Well TZ83 decreased from 1.23 mm/a to 0.025 mm/a and the corrosion rate of Well TZ623 decreased from 0.370 mm/a to 0.016 mm/a.

Corrosion Evaluation of NiCrAlCoY Coating Applying Electrochemical Noise and Lineal Polarization Resistance Techniques

Kinetics corrosion of NiCrAlCoY thermal flame spray coating are reported. This coating was exposed to LiBr-H2O (wt. 50%) at 25 and 70°C during 10 days. The electrochemical noise (EN) technique and lineal polarization resistance (LPR) were applied. NiCrAlCoY coating was tested as sprayed condition and polished condition. These two different conditions were chosen in order to determine the effect of porosity and homogeneity of the surface. The resistance noise (Rn) was determined from the EN measurements, and Rn together with LPR were compared. Considering that the corrosion resistance is the inverse of the corrosion rate, it is stated that at 25°C the corrosion rate was higher in the polished condition coatings. At 75°C, this behavior was only observed through the LPR results. Probably, this discrepancy between both techniques was because of the determination of Rn was made statistically considering localized events. In general, the passive layer formed after spraying protects the coating generating major corrosion resistance.

선박의 해양 부식과 부식방지 장치

Ships and offshore structures are exposed to harsh marine environments, and maintenance and repair are becoming increasingly important to the industry and the economy. The major corrosion phenomenons of metals and alloys in marine environment are pitting corrosion, stress corrosion cracking, crevice corrosion, fatigue corrosion, cavitation-erosion and etc. due to the effect of chloride ions and is quite serious. Methods of protection against corrosion can generally be divided into two groups: anodic protection and cathodic protection. Anodic protection is limited to the passivity characteristics of a material in its environment, while cathodic protection can apply methods such as sacrificial anode cathodic protection and impressed current cathodic protection. Sacrificial anode methods using Al and Zn alloys are widely used for marine structures and vessels intended for use in seawater. Impressed current cathodic protection methods are also widely used in marine environments, but tend to generate problems related to hydrogen embrittlement caused by hydrogen gas generation. Therefore, it is important to the proper maintenance and operation of the various corrosion protection systems for ship in the harsh marine environment.

Identification, quantification and localization of secondary minerals in mixed Fe0 fixed bed reactors

Passivating secondary minerals in mixed Fe0 reactive fixed bed filters for the reductive dechlorination of chlorinated hydrocarbons were investigated with different techniques. Uncemented cast iron grains were obtained from long term corrosion experiments. Magnetite and chukanovite were identified as major corrosion products. Gravimetric and sieve analyses revealed a strong influence of inorganic carbon on corrosion product buildup. Surface area analyses indicated that magnetite, together with cryptocrystalline corrosion products, increase the surface area more than chukanovite. A heterogeneous morphology was found in corrosion products formed in deionized water by scanning electron microscopy. Corrosion products formed in the presence of inorganic carbon revealed a homogeneous and almost completely covering layer. Transects were analyzed with backscatter electron detection. Electron microscopic investigations on the cross sections of gravel and cast iron granules indicated that corrosion products only occur on reactive surfaces. Additional dissolution and washing procedures confirmed that corrosion products do not grow or precipitate on non-reactive interfaces. The results indicate that precipitation out of the solution plays a minor role compared with the growth of corrosion products on the iron surface.

Effect of bismuth and silver on the corrosion behavior of Sn–9Zn alloy in NaCl 3wt.% solution

Abstract The effect of silver (Ag) and bismuth (Bi) on the corrosion resistance of Sn–9Zn alloy in NaCl 3 wt.% solution was investigated using electrochemical techniques. The results showed that the addition of Bi and Ag lead to the increase of corrosion rate and the corrosion potential Ecorr is shifted towards less noble values. After immersion, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive of spectroscopy (EDS) analysis of the corroded alloy surface revealed the nature of corrosion products. EDS and XRD analyses confirmed the oxide of zinc (ZnO and Zn5(OH)8Cl2H2O) as the major corrosion product formed on the outer surface of in the tested three solder alloys.

A Review of Different Sensors Applied to Corrosion Detection and Monitoring

Between 1999 and 2001, corrosion-related costs accounted for 3.1% of the Gross Domestic Product (or $276 billion a year) in the US. To minimize the economical loss requires accurately predicting and effectively preventing corrosion. Generally, corrosion is the deterioration of metal by its interaction with a combination of physical and chemical environments. Therefore, corrosion detection can be indirectly achieved by monitoring the accumulation of corrosion products or the physical or chemical changes they cause, e.g. appearance, acoustic and electromagnetic transmission, pH, etc. On the other hand, corrosion can be directly monitored by its electrochemical characteristics such as corrosion current, electrochemical noise, corrosion potential. Each of these corrosion monitoring techniques is worth its own fulfilled discussion. Instead of go through each techniques exhaustively, we will just give a general review of the major corrosion monitoring techniques across different research areas, with the intention of a contribution to the interdisciplinary research of corrosion monitoring techniques.

Combining Raman Microprobe and XPS to Study High-Temperature Oxidation of Metals

Raman microprobe spectroscopy was applied in studies of high-temperature air oxidation of a ferritic alloy (HT-9) in the absence and presence of zirconia coatings with the objective of evaluating the technique as a way to quickly screen candidate cladding materials and actinide-based mixed oxide fuel mixtures for advanced nuclear reactors. When oxidation was relatively uniform, Raman spectra collected using microscope optics with low spatial resolution were found to be similar to those collected with conventional Raman spectroscopy. These spectra could be used to identify major oxide corrosion products and follow changes in the composition of the oxides due to heating. However, when the oxidation films were comprised of multiple layers of varying composition, or with layers containing metallic phases, techniques with higher depth resolution and sensitivity to zero-valence metals were necessary. The requirements were met by combining Raman microprobe using different optical configurations and x-ray photoelectron spectroscopy.