Corrosion Product Film Research Articles

Sour Top-of-the-Line Corrosion in the Presence of Acetic Acid

Abstract Under stratified flow and dewing conditions, internal corrosion can occur at the top of horizontal pipelines where continuous injection of corrosion inhibitors does not have a mitigating effect. This research work presents an experimental study of the influence of the presence of hydrogen sulfide (H2S; up to 0.13 bars) and acetic acid (HAc; up to 1,000 ppm) on carbon dioxide (CO2) top-of-the-line corrosion. The study was performed in a 10 cm (4 in) internal diameter flow loop with system conditions constant at 70°C, 2 bars partial pressure CO2, 3 bars total pressure, 5 m/s gas velocity, and a water condensation rate of 0.25 mL/m2/s. A comprehensive analysis on the effect of these parameters (partial pressure of H2S and concentration of acetic acid) on the type of corrosion product film formed at the top of the line is performed.

The effect of epoxy coating containing emeraldine base and hydrofluoric acid doped polyaniline on the corrosion protection of AZ91D magnesium alloy

Corrosion protection of epoxy coatings containing emeraldine base polyaniline (PANI) or hydrofluoric acid doped PANI on AZ91D magnesium alloy were studied by EIS and Pull-Off Adhesion Test. The results indicated that the addition of emeraldine base PANI or hydrofluoric acid doped PANI could improve the corrosion resistance of epoxy coating. The epoxy coating containing hydrofluoric acid doped PANI had the best performance of the corrosion protection among three systems under investigation. The corrosion product film was analyzed by XPS indicating that PANI changed the chemical structure of the corrosion film. The protective mechanism imparted by PANI was discussed.

Impact of SO 2 concentration on the corrosion rate of X70 steel and iron in water-saturated supercritical CO 2 mixed with SO 2

The corrosion behavior of X70 steel and iron in water-saturated supercritical CO 2 mixed with SO 2 was investigated using weight-loss measurements. As a comparison, the instantaneous corrosion rate in the early stages for iron in the same corrosion environment was measured by resistance relaxation method. Surface analyzes using SEM/EDS, XRD and XPS were applied to study the morphology and chemical composition of the corroded sample surface. Weight-loss method results showed that the corrosion rate of X70 steel samples increased with SO 2 concentration, while the corrosion rate increased before decreasing with SO 2 concentration for iron sample. Comparing resistance relaxation method results with weight-loss method results, it is found that the instantaneous corrosion rate of iron is much higher than the uniform corrosion rate of the iron tablet specimens which are covered with thick corrosion product films after a long period of corrosion. The corrosion product films were mainly composed of FeSO 4 and FeSO 3 hydrates. The possible reaction mechanism under such environment was also analyzed, and the electrochemical reaction between the dissolved SO 2 in the condensed water film with iron is the critical reaction step.

Corrosion behavior of novel imitation-gold copper alloy with rare earth in 3.5% NaCl solution

A novel imitation-gold copper alloy with rare earth was designed and prepared. The corrosion behavior of the alloy immersed in 3.5% NaCl solution and its anti-tarnish property in the salt spray for different days has been studied. The designed alloy (CuZnAlNiMeRe) has more excellent anti-tarnish property and lower corrosion rate than those of currency coinage materials of H7211 alloy (used in China). A uniform and compact of corrosion film has been formed after the designed alloy immersed in 3.5% NaCl solution. The corrosion current densities I corr of the alloy decreased while the polarization resistance R p increased with time. The capacitance of the corrosion product film C film of the alloy decreased while the charge transfer resistance R ct. The Warburg diffusion impedance W R and the resistance of the equivalent circuit R increased with time.

Influence of Nd and Y additions on the corrosion behaviour of extruded Mg-Zn-Zr alloys

To improve the corrosion resistance of wrought magnesium alloys through rare earth (RE) additions, the corrosion behaviour of Mg-5Zn-0.3Zr-xNd (x=0, 1, and 2; wt%) and Mg-5Zn-0.3Zr-2Nd-yY (y=0.5 and 1; wt%) alloys in a 5wt% NaCl solution was investigated using immersion test and electrochemical measurements. The results of immersion test show that Mg-5Zn-0.3Zr-2Nd alloy exhibits the best corrosion resistance among the tested alloys. Electrochemical measurements show that secondary phases in RE-containing Mg-5Zn-0.3Zr alloys behave as less noble cathodes in micro-galvanic corrosion and suppress the cathodic process. The additions of Nd and Y into Mg-5Zn-0.3Zr alloy also improve the compactness of the corrosion product film and are beneficial to the corrosion resistance.

Ellipsometric analysis of corrosion behavior of 3C magnesium alloy surface touched by simulated sweat

AbstractAs an optimum shell material, AZ80 magnesium alloys are widely applied in the 3C (computers, communications and consumer electronics) industries. The case of 3C products corroded by a sweaty hand has been simulated and the corrosion characters have been investigated by ellipsometric technology. Thickness variation of corrosive medium film on a Mg alloy surface was monitored. Surface structure of a corrosion layer was described with a three‐layer optical model (substrate—EMA—Cauchy) and thickness of each layer for different soaking time was obtained by fitting experimental data with the model. The corrosion product films with a refractive index of 1.45–1.62, loose corrosion product layer, can only provide limited protection to the substrate when a Mg alloy surface is corroded by sweat again. Copyright © 2010 John Wiley & Sons, Ltd.

Electrochemical corrosion behaviour of Sn–Ag–Cu (SAC) eutectic alloy in a chloride containing environment

AbstractThe corrosion behaviour of the Sn94.5Ag3.8Cu1.5 (SAC) eutectic alloy was investigated in 0.1 M NaCl solution by potentiodynamic polarization and impedance spectroscopy measurements and compared with that of the conventional Sn73.9Pb23.1 eutectic solder employed for a long time in the packaging of microelectronic components and devices. Scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) were used to characterize the SAC eutectic alloy prior to and after the electrochemical tests. The electrochemical results indicated that the Sn–Ag–Cu eutectic alloy exhibits better corrosion behaviour than the Sn–Pb eutectic solder in NaCl solution. The presence of a corrosion products layer constituted by tin oxy‐chloride was detected at the surface of both alloys investigated after the electrochemical tests. The better corrosion behaviour of SAC eutectic alloy compared to Sn–Pb eutectic solder is ascribed to the formation of a more compact surface film of corrosion products with improved protective properties owing to the presence of copper and silver, as revealed by EPMA.

Errosion-Corrosion Critical Performance of Surface Nanocrystalline 20 Carbon Steel in Condensate Water

In this paper, the ultrasonic shot peening (USSP) technology was used to obtained surface nanocrystalline of 20 carbon steel. The grain size of test surface and the thickness of nanocrystallization layer were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The three electrode electrochemical measurement was employed to investigate the electrochemical corrosion performance and the critical character of USSP surface nanocrystallization samples in different impact strength. The results showed that the USSP surface nanocrystallization could obtain the nanocrystalline grain. The thickness of nanocrystallization layer increased and grain sizes reduced with the increase of the impact strength. Nanocrystallization layer took the way to expand concentric circles with impact crater as the center. The corrosion current of nanocrystallization sample was much larger than as-received. The controlled step of corrosion process was turned from cathodic process to anodic process by USSP surface nanocrystallization. The sample surface formed two layers corrosion product films in condensate water, which were compact Fe3O4membrane as inner corrosion product film and loose Fe3O4membrane or Fe2O3membrane as outer layer. With the increase of the impact strength, critical velocity of the outer corrosion product film increased gradually. The critical velocity of inner corrosion product film had an increasing trend, but the critical velocity tended to be a constant value when impact strength was more than 1.9904min/cm2

Microstructure and Anti-Corrosion Properties of Arc-Sprayed Aluminum Coating in Splash Zone

Aluminum coatings were developed by arc spray on mild carbon steel Q235. Scanning electron microscopy detection shows that the coatings have good bonding with the substrate and have low porosity. The corrosion behaviors of the coatings in splash zone were studied. The results show that free corrosion potentials of aluminum coatings are much lower than that of Q235. Potentiodynamic polarization measurements reveal that the curves of aluminum coatings have activity anodic dissolution zone, passivation zone and super-passivation zone. Corrosion morphology and energy dispersive spectrometers show that Cl- can penetrate into the coatings and some of the substrate has been corroded. The arc spray Al-coating develops a film of corrosion products on the coating surface, which tend to seal the pores in the coatings. Arc spray aluminum coatings can protect the substrate from corrosion in splash zone.

Effect of zinc addition to copper in improving its corrosion resistance in sulfide polluted synthetic seawater

In an endeavor to develop a cost effective substitute of Cu-10Ni alloy for seawater application (especially for sulfide polluted seawater) few Cu-Ni-Zn-Mn alloys were developed in our laboratory. The Cu-Ni-Zn-Mn alloy was found to have better corrosion resistance than Cu-10Ni both in clean and sulfide polluted synthetic seawater. Resistance to sulfide in Synthetic Seawater was attributed to the formation of ZnS. To ensure that the resistance to sulfide attack is due to Zn alone, a series of studies were carried out with binary alloys of Cu and Zn with increasing weight percentage of Zn (12% and 36%). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) was used for the purpose. Polarization studies gave the corrosion data and EIS was effective in depicting the nature of corrosion product (film). It was found that among the test alloys, Cu-36Zn is most corrosion resistant in sulfide polluted seawater due to formation of ZnS in the film. As it is a binary alloy, the corrosion resistance against sulfide is attributed to Zn alone.

Stress corrosion cracking of aluminium alloy 7075(w) under tensile and compressive loading

The effect of compressive loading on stress corrosion cracking of aluminium alloy 7075(W) was studied using specimens containing simulated fastener holes and the results were compared with the behaviour of double cantilever beam specimens with tensile loading. Crack lengths were measured with an eddy current bore probe and confirmed by optical metallography. Intergranular stress corrosion was observed in both tensile and compressive loading. Cracks initiated readily in 3·5%NaCl solution with tensile loading and the alloy was much less susceptible in compression, with cracking being detected only after 14 day exposure to EXCO solution. No cracking was observed in unstressed specimens, even after 56 day continuous exposure to EXCO solution. In both cases, SCC was explained by an active path mechanism due to the galvanic interaction between grain boundary precipitates and adjacent precipitate free zones. Compressive loading produced a positive strain at the crack tip, which ruptured the protective corrosion product film, maintaining the path of preferential corrosion.

The growth mechanism of CO 2 corrosion product films

Carbon steel usually has high corrosion rate in water with dissolved CO 2 however the steel surface can be covered by protective corrosion product film. Therefore the carbon steel can be widely used in oil and gas industry. This paper discusses the structure, electrochemistry performances, initiation and growth of protective corrosion product films. A duplex layer structure of FeCO 3 films was found by electrochemical impedance spectrum (EIS). The physical and chemical situations of solution near carbon steel surface were investigated by ultraviolet spectrophotometry and chronopotentiometry. According to crystallography the growth mechanisms of protective CO 2 corrosion product films were discussed.

Effect of Ce on microstructure, mechanical properties and corrosion behavior of high-pressure die-cast Mg–4Al-based alloy

Mg–4Al– xCe–0.3Mn ( x = 0, 1, 2, 4 and 6 wt.%) alloys were prepared by high-pressure die-casting. The microstructures, mechanical properties and corrosion behavior were investigated. The cross-section of test bar is divided into the fine skin region and the relatively coarse interior region by a narrow band. The dendritic arm spacing is greatly reduced and the secondary phases Al 11Ce 3 and (Al, Mg) 2Ce with the former being the dominant one substitute the Mg 17Al 12 phase with addition of Ce. When Ce content reaches 4 wt.%, the alloy exhibits an optimal cost performance ratio. The improved mechanical properties maintained up to 200 °C are mainly related to the fine grain size and the main strengthening phase Al 11Ce 3, which is present in a high volume fraction, and possesses fine acicular morphology and relatively good thermal stability. The improved corrosion resistance is attributed to the microstructure modification of the alloys and the corrosion product films.

Electrochemical corrosion behavior of X80 pipeline steel in a near‐neutral pH solution

AbstractIn this work, the electrochemical corrosion behavior of X80 pipeline steel was investigated in a near‐neutral pH solution using electrochemical impedance spectroscopy (EIC) and photo‐electrochemical (PEC) measurements as well as X‐ray photo‐electron spectroscopy (XPS) technique. The effects of hydrogen‐charging and stress were considered. The results show that the steel is in an active dissolution state, and a layer of corrosion product is formed and deposited on the electrode surface, which is subjected to further oxidation to form ferric oxide and hydroxide. Photo‐illumination enhances anodic dissolution of the steel when it is under anodic polarization due to destroying of the corrosion product film. When the steel is under cathodic polarization, the cathodic current density decreases upon laser illumination due to the photo‐oxidation of hydrogen atoms generated during cathodic reactions, which behaves as an anodic reaction to offset the cathodic current density. Hydrogen‐charging and stress decrease the corrosion resistance of the steel and enhance the dissolution rate of the steel.

H2S and O2 influence on the corrosion of carbon steel immersed in a solution containing 3M diethanolamine

Aqueous solutions with 3 mol L −1 (M) diethanolamine (DEA) concentration are extensively used in the gas processing industry to remove acid gases. However, the degradation of the DEA and the formation of heat-stable salts (HSS) lead to severe corrosion problems. Even worse, equipment corrosion can be magnified by the unavoidable presence of sulphide acid and dissolved oxygen as a result of hydrocarbon (natural gases and crude oil) processing. The aim of this work is to study the combined corrosion effects of DEA, sulphide acid and oxygen on carbon steel. Electrochemical methods revealed that in the 3 M DEA medium without oxygen, corrosion processes are modulated by adsorbed DEA film formation. Furthermore, it was shown that the addition of oxygen and 15 × 10 −3 mol L −1 (15 mM) H 2 S produced the formation of an adherent film on the carbon steel surface. Chemical analyses by EDAX revealed a homogeneous film of corrosion products composed of iron oxide and sulphide formed in DEA solution containing O 2 and H 2 S, respectively. Equivalent circuits were used to estimate the parameters associated with ion diffusion through the formed corrosion films. The results showed that the presence of H 2 S induced the formation of thin iron sulphide films that provide protective properties to the metal. It is concluded that the presence of oxygen in a sweetening plant should be avoided as DEA degradation can be produced with the subsequent decrease in chelating process efficiency and the increase in corrosion problems.

Oil Wetting and Carbon Dioxide Corrosion Inhibition of Carbon Steel with Ferric Corrosion Products Deposits

Abstract Wettability of carbon steel with corrosion product films (iron carbonate [FeCO3], FeCO3 with oxidized surface, and rust [FeO(OH)]) was investigated through contact angle and inhibitor performance tests. Two corrosion inhibitors, an oleic imidazoline compound (OI) and a phosphate ester compound (PE), were used. The inhibitor performance was studied in carbon dioxide (CO2) corrosion tests at 60°C, 1 bar CO2, 3 wt% sodium chloride (NaCl), and 20 vol% oil, where the samples were alternately exposed to oil and aqueous phase. A refined, low aromatic oil was used in the tests. Addition of both inhibitors lead to significant changes in the wettability of oxidized FeCO3 surfaces. The contact angle tests showed that a transition from a preferential water-wet state to a preferentially oil-wet state was achieved for both inhibitors. Electrochemical measurements indicated that addition of OI enabled the oxidized FeCO3 surface to retain an oil film after immersion in oil. Electrochemical impedance spectra (EIS) measurements revealed a significant increase in the measured, uncompensated resistance at high frequencies after immersion in oil. The apparent retained oil film caused a significant drop in corrosion rate in aerated solutions. The reduction in corrosion rate remained stable even after a return to a CO2-saturated solution. A similar effect was also seen on a rusting carbon steel surface. No significant lasting effect of oil exposure was seen for PE in the inhibitor performance tests.

Mesh-capped probe design for direct pH measurements at an actively corroding metal surface

Quantitative characterization of surface reaction species improves understanding of reaction mechanisms, especially for heterogeneous reactions such as in corrosion and electrolysis. A universal mesh-capped surface pH probe was developed in order to investigate surface proton concentrations for aqueous metal dissolution/deposition reactions. This technique can be generally applied to characterize the surface pH either for bare metal reactions or metals corroding beneath a corrosion product film. Measurements with the new probe design have shown a good degree of reproducibility. The surface pH measurements during corrosion of mild steel have shown that a higher surface pH is achieved at the steel surface as compared with that of the bulk solution, just as predicted from theory. Chemical buffering effects on surface pH were observed during corrosion by contrasting the measurements obtained in HCl deaerated solutions with those containing CO2, i.e., carbonic acid (H2CO3) and acetic acid (CH3COOH/HAc) solutions. It was found that the surface pH was mainly controlled by the water chemistry and chemical buffer capacity. The surface pH is affected by the deposited corrosion scale porosity. A higher deviation of surface pH compared to the bulk value was observed for more dense layers with lower porosity.

A Study on the Accuracy of the Tafel Extrapolation Method in HCl

Accuracy and validity of the Tafel extrapolation method for determining corrosion rates of carbon steel in 1,2 and 3M HCl solutions open to air is discussed. Corrosion rates obtained from polarization experiments were compared with that of weight loss method. For analysing data obtained from polarization experiments electrochemical impedance spectroscopy (EIS) measurements were performed before polarization experiments. The results showed that formation of a corrosion product film and increasing the polarization resistance (Rp) of this film with time cause the corrosion rates obtained from Tafel extrapolation tend to be higher than corrosion rates obtained from weight loss test.

Comparative study on the electrochemical performance of the Cu–30Ni and Cu–20Zn–10Ni alloys

Abstract The electrochemical performance of the Cu–20Zn–10Ni alloy was compared with that of the Cu–30Ni alloy in a 3.5 wt.% sodium chloride solution. Electrochemical impedance spectroscopy (EIS) measurements show that, interestingly, both the increasing rates of the thickness and resistance of the passive film formed on the Cu–20Zn–10Ni alloy are larger than those of the passive film formed on the Cu–30Ni alloy during the immersion of the two alloys in the 3.5 wt.% NaCl solution. The passive film formed on the Cu–20Zn–10Ni alloy surface is found to have a higher resistance and thicker depth than that formed on the Cu–30Ni alloy surface after the immersion of the two alloys in the 3.5 wt.% NaCl solution for 120 h. To some extent, the Cu–20Zn–10Ni alloy could substitute for the Cu–30Ni alloy in a corrosive environment containing chloride ions. According to X-ray diffraction and scanning electron microscopy studies, the corrosion product films of the Cu–20Zn–10Ni alloy were found to consist of two layers, with the inner layer and the outer layer being composed of cuprous oxide and (Cu, Zn) 2 Cl(OH) 3 , respectively, while the corrosion product films of the Cu–30Ni alloy were found to consist mainly of (Cu, Ni) 2 Cl(OH) 3 .

Investigation of a New Dry Surface Decontamination Technology with Low-Pressure ArcPlasma and Its Application to Pipe-Shaped Test Pieces

We investigated a dry surface decontamination technology using low-pressure arc plasma for radioactive corrosion product films. The low-pressure arc plasma is produced with a transferred-type DC arc discharge that operates under reduced pressure; here, the cathode is the object to be treated. The cathode spots formed inside the low-pressure arc plasma can melt away the metal oxide film on the surface of the object without significantly damaging the metal substrate. One of the major advantages of this technology is its potential to reduce the amount of secondary waste compared with existing technologies, e.g., decontamination with chemical solutions, because it eliminates the need for a medium. In this report, the dependence of the decontamination performance on the type of plasmasource gas was investigated. Argon, hydrogen, chemically active carbon monoxide, and a mixed gas of CF4/O2 were selected. Consequently, a higher Cobalt-60 removal ratio was obtained with smaller electric charges in the hydrogen low-pressure arc plasma. The low-pressure arc plasma was also applied to pipe-shaped test pieces with a corrosion product film. And eventually, a Co removal ratio exceeding 90% was achieved. The applicability of the dry surface decontamination technology with low-pressure arc plasma for radioactive metal waste with a corrosion product film is demonstrated.