Showing papers in "British Corrosion Journal in 2002"
TL;DR: In this article, the performance of some ferrous alloys at depths of 500, 1200, 3500, and 5100 m in the Indian Ocean has been studied and the results of atomic absorption spectroscopy have revealed that the corrosion product present on mild steel coupons is FeOOH.
Abstract: The deep sea corrosion of ferrous alloys that undergo uniform corrosion without forming a passive layer is related to the amount of dissolved oxygen available in the sea water. The performance of some ferrous alloys at depths of 500, 1200, 3500, and 5100 m in the Indian Ocean has been studied. The results of atomic absorption spectroscopy have revealed that the corrosion product present on mild steel coupons is FeOOH. The results of experiments in shallow water have shown that micro- and macrobiological growths play a significant role in the corrosion of ferrous materials. However, in deeper waters, the absence of macrofouling was evident, and corrosion was not related to any biological product but mainly to the electrochemical reaction of these alloys with sea water. The results of morphological studies by SEM on the surfaces of exposed specimens are also presented.
65 citations
TL;DR: In this article, the effect of sodium n,n-diethyl dithiocarbamate (SDEDTC) on the corrosion of mild steel in 0·5 mol L-1 HCl solution was studied using weight loss and potentiodynamic polarisation methods.
Abstract: The effect of sodium n,n-diethyl dithiocarbamate (SDEDTC) on the corrosion of mild steel in 0·5 mol L-1 HCl solution was studied using weight loss and potentiodynamic polarisation methods. Experimental data revealed that SDEDTC acted as an inhibitor in the acid environment and, furthermore, that the compound was a mixed type inhibitor, predominating as a cathodic inhibitor. It was found that the inhibition efficiency increased with an increase in SDEDTC concentration at temperatures in the range 303–333 K. The experimental data for the inhibitor fitted the Flory–Huggins adsorption isotherm and the El–Awady thermodynamic kinetic model. The corrosion inhibition mechanism of SDEDTC on mild steel in HCl solution was also investigated by infrared spectra and electron probe microanalysis methods. The process of inhibition is attributed to the formation of an adsorbed film on the metal surface, which protects the metal against corrosive agents.
43 citations
TL;DR: In this paper, three organic inhibitors containing heteroatoms were synthesized in the lab and their inhibiting action on the corrosion of carbon steel in 1N HCl was investigated by means of two different techniques, namely weight loss and potentiodynamic studies.
Abstract: Three organic inhibitors containing heteroatoms, namely: undecenoic acid hydrazide (UAH); 2-mercaptobenzothiazole (MBT); and 2-hydrazinobenzothiazole (HBT) have been synthesised in the lab and their inhibiting action on the corrosion of carbon steel in 1N HCl was investigated by means of two different techniques, namely weight loss and potentiodynamic studies. The weight loss studies were conducted in 1MHCl at different temperatures (30, 45, and 60°C) using various concentrations (25–500 ppm) of the inhibitor, and the inhibitor with the highest efficiency (HBT) was also tested for different immersion times (1/2, 3, 6, and 24 h) at the optimum concentration (500 ppm) at room temperature (30°C). The results show that the inhibitor efficiency increases with increased temperature, from room temperature (30°C) to 60°C at the most effective concentration (500 ppm). Inhibitor efficiency (IE) also increases with increase in the inhibitor concentration from 25 to 500 ppm at a given temperature and time. T...
41 citations
TL;DR: In this article, the authors used double cantilever beam and slow strain rate tensile specimens to measure the susceptibility of a 900 MPa yield strength steel in different marine environments, ranging from sterile sea water and filtered natural sea water to open sea water, and seabed sediment.
Abstract: Hydrogen embrittlement tests were carried out using double cantilever beam and slow strain rate tensile specimens to measure the susceptibility of a 900 MPa yield strength steel in different marine environments, ranging from sterile sea water and filtered natural sea water to open sea water and seabed sediment. The cathodic protection potential and the presence of biologically generated sulphides in seabed sediment were shown to be important factors that controlled the extent of hydrogen uptake and embrittlement. Threshold stress intensities Kth were measured for each condition and the optimum cathodic protection potential to control corrosion with the minimum risk of embrittlement was established.
32 citations
TL;DR: In this article, the applicability of various techniques for the assessment and quantification of sensitisation in AISI Type 316L welds was discussed, and the possibility of using eddy current testing (ECT) to detect sensitisation and intergranular corrosion was also assessed.
Abstract: This paper deals with the applicability of various techniques for the assessment and quantification of sensitisation in AISI Type 316L welds. Welded joints of AISI Type 316L stainless steel were aged at 973 K for periods of up to 200 h. The base and weld metal components of the aged joints were then assessed for susceptibility to sensitisation and intergranular corrosion (IGC) by using various tests specified by ASTM A262, Practices A and E, and ASTM G108 (the electrochemical potentiokinetic reactivation (EPR) test). The possibility of using eddy current testing (ECT) to detect sensitisation and IGC was also assessed. The use of ASTM A262 Practice A and E tests indicated sensitisation in base metal aged for 20 h and above. Aged weld metals showed no failure in these tests. Tensile tests on the weld joints before and after exposure to Cu–CuSO4-H2SO4 solution did not indicate any differences in the tensile properties. Double loop EPR tests indicated a significant increase in the ratios of charge an...
26 citations
TL;DR: In this article, an investigation has been carried out to assess the zinc runoff from a variety of galvanised materials over 16 months at the industrial/marine Port Talbot weathering site.
Abstract: An investigation has been carried out to assess the zinc runoff from a variety of galvanised materials over 16 months at the industrial/marine Port Talbot weathering site. Over 16 months of exposure, bare zinc, and Electrozinc have the highest levels of zinc runoff (4·38 and 4·20 g m-2) followed by general galvanised steel substrates, i.e. hot dip galvanised (HDG) steel (0·15 wt-%Al) (2·87 g m-2) and iron zinc intermetallic galvanised steel (galvanneal, 2·36 g m-2). Galvanneal (IZ) has a higher initial runoff rate than HDG due to the presence of iron/zinc intermetallic in the coating that promotes anodic zinc dissolution. The HDG has a more constant runoff rate that exceeds IZ after 7-8 months due to build up of corrosion products on the IZ surface. Aluminium/zinc alloy coated steels have a much lower runoff rate than general galvanised materials as the aluminium present in the structure provides a strongly protective oxide barrier coating improving corrosion resistance (Galfan 5 wt-%Al, 2·04 g m-...
23 citations
TL;DR: In this paper, the effects of 3,5 bis (2-pyridil) 4-amino 1,2,4 triazole (NBTA) and 1-10 phenantrolin (PHEN) on corrosion of mild steel in acid solutions, (sulphuric acid and hydrochloric acid) were studied.
Abstract: The inhibition effects of 3,5 bis (2-pyridil) 4-amino 1,2,4 triazole (NBTA) and 1-10 phenantrolin (PHEN) , on corrosion of mild steel in acid solutions, (sulphuric acid and hydrochloric acid) were studied. The Tafel polarisation and ac impedance techniques were employed. Results obtained reveal that both compounds are relatively good inhibitors. The inhibition efficiencies of NBTA are higher in hydrochloric acid than in sulphuric acid. This has been attributed to the synergistic effect of chloride ions present in hydrochloric acid. The mechanism of inhibition of PHEN is believed to be owing to the formation of insoluble chelates between the organic molecules and atom/ion on the metal surface. The adsorption of NBTA is believed to occur through the formation of an iron-nitrogen coordinate bond. The adsorption isotherms were also determined and found to be of the Langmuir type.
21 citations
TL;DR: The effectiveness of ammonium monocarboxylates decreased with increase in the length of the carbon chain of the carboxylic acid as mentioned in this paper, while the other carboxylate did not show such a clear trend.
Abstract: Fifty three products, mostly carboxylate salts of amines, were evaluated as vapour phase corrosion inhibitors for mild steel. Fifteen compounds showed effectiveness in excess of 90%. Morpholine was the most effective amine and caprylic acid the most effective acid constituent. The effectiveness of ammonium monocarboxylates decreased with increase in the length of the carbon chain of the carboxylic acid. The other carboxylates did not show such a clear trend.
21 citations
TL;DR: In this article, the anodic behaviour of X-ray amorphous and heat-treated high P electroless Ni-P deposits investigated by potentiodynamic and potentiostatic methods in acidic aqueous chloride solutions was reported.
Abstract: This paper reports on the anodic behaviour of as plated (X-ray amorphous) and heat treated (crystalline) high P electroless Ni-P deposits investigated by potentiodynamic and potentiostatic methods in acidic aqueous chloride solutions. Potentiodynamic measurements show an active-passive behaviour for both structures. The valence of P dissolution was assessed by the weight loss v. charge technique; dissolution valences do not correlate clearly with potentiodynamic behaviour. This can nevertheless be clearly interpreted in terms of ex situ X-ray photoelectron spectroscopy analyses of attacked layer composition; the layers formed at lower anodic potential within the passive range consist of NiO, the ones obtained at high anodic polarisation contain phosphate. Differences in anodic behaviour of as plated and heat treated specimens can be explained in terms of the defectiveness of protective NiO layers as a function of grain boundaries emerging at the surface.
17 citations
TL;DR: In this article, sets of mild steel coupons of the same exposed areas but having different perimeters were immersed in a marine environment and mass loss was observed for area/perimeter ratios in the range 3·52-6·03%.
Abstract: The conventional wisdom in corrosion testing is that the size of the coupon and its perimeter/area ratio (the surface area of the perimeter expressed as a percentage of the total surface area) are important parameters and that these will have an effect on the results obtained. In order to test this proposition, sets of mild steel coupons of the same exposed areas but having different perimeters were immersed in a marine environment. Corrosion mass loss was observed for area/perimeter ratios in the range 3·52-6·03%. Mass loss observations were taken at various times to 12 months. Sets of rectangular coupons of different sizes (50 × 100 mm and 100 × 200 mm) were also immersed. The results indicate that any variation caused by shape or size falls within the expected variability of corrosion at a test location.
17 citations
TL;DR: In this paper, the effect of phosphate ions on the corrosion behavior of copper in sulphate solutions was investigated at different temperatures (293, 313, 333, and 353 K) and at different pH values (pH = 2·1, 7·2, and 12·3).
Abstract: The effect of phosphate ions on the corrosion behaviour of copper in sulphate solutions was investigated at different temperatures (293, 313, 333, and 353 K) and at different pH values (pH = 2·1, 7·2, and 12·3). A three electrode electrochemical technique was used for the measurements, using a saturated calomel electrode (SCE) for reference purposes. Both anodic and cathodic polarisation curves were established, from which the anodic and cathodic Tafel constants were determined. Corrosion potentials were determined by extra trapolation of the anodic and cathodic Tafel lines to the point of zero current density. The results showed that for a pH value of 2·1, the corrosion rate of copper showed a marked tendency to increase with increasing temperature in solutions containing either sulphate alone or sulphate plus phosphate. However, at pH values of 7·2 and 12·3, this tendency became less pronounced in solutions containing sulphate alone and in solutions containing sulphate plus phosphate together, ...
TL;DR: In this paper, the electrochemical behaviour under slurry erosion-corrosion and the transient electrochemical response under single impact of three stainless steels (UNS S31254, UNS S32654, and UNSS32750) is assessed.
Abstract: Erosion-corrosion by liquid-solid impact results in damage on high alloy stainless steels where slurries are transported through pipes, valves, and pumps It is well recognised that this damage is caused by a complex combination of mechanical (impact) and electrochemical (corrosion) processes The synergy between erosion and corrosion is significant and depends on the nature of the materials and the aqueous environment As part of a wider study investigating the mechanisms or erosion-corrosion of high alloy stainless steels, a series of electrochemical tests under multiple particle erosion-corrosion conditions and single impact conditions have been performed In this paper the electrochemical behaviour under slurry erosion-corrosion and the transient electrochemical response under single impact of three stainless steels (UNS S31254, UNS S32654, and UNS S32750) is assessed The depassivation and repassivation characteristics of the surface are characterised and these results are discussed in relati
TL;DR: The effect of NOx purging on the corrosion behavior of stainless steel in hot 8M nitric acid has been investigated in this article, where it is shown that NOx is shown to reduce the redox potential of the solution, but in the absence of other dissolved species acts as an oxidising agent to stainless steel and increases the corrosion rate.
Abstract: The effect of NOx purging on the corrosion behaviour of stainless steel in hot 8M nitric acid has been investigated. Gravimetric corrosion rate measurements and electrochemical potential and polarisation data made on nitric acid grade (NAG) 18/10L stainless steel are related to the concentration of nitrous acid produced by NOx purging, which in turn is related to the solution redox potential measured using clean Pt. Purging with NOx is shown to reduce the redox potential of nitric acid solution, but in the absence of other dissolved species acts as an oxidising agent to stainless steel and increases the corrosion rate. T he effect of NOx purging saturates at relatively low flow rate owing to the fact that the solution becomes saturated with nitrous acid. However, in 8M nitric acid containing 3 g L-1 Fe and 0·7 g L-1 Ru at 100°C, NOx purging has no effect on the corrosion rate of NAG 18/10L. This is considered to indicate that Fe and Ru at these concentrations polarise stainless steel to the same ...
TL;DR: In this paper, the electrochemical behavior of two copper nickel alloys; cu-20 wt-%Ni and Cu-80 wt -%Ni, was studied in alkaline solution using the cyclic voltammetric technique.
Abstract: The electrochemical behaviour of two copper nickel alloys; cu-20 wt-%Ni and Cu-80 wt-%Ni, was studied in alkaline solution using the cyclic voltammetric technique. The voltammograms of the alloys were compared with those of the pure copper and pure nickel recorded under the same conditions. The influence of different variables such as switching potential Es, scan rate, NaOH concentration, solution temperature, and repetitive cycling was also studied. The forward sweep was characterised by the appearance of five anodic peaks: A1, A2, A3, A4, and A5, which are related to the formation of Ni(OH)2, Cu2O, Cu(OH)2, CuO, and Ni2O3, respectively. The activity of copper dissolution and, hence, the heights of the corresponding anodic peaks decreased as the nickel content in the alloy increased. X-ray diffraction analysis of the surface of the 80% nickel alloy after polarisation in the anodic direction confirmed the existence of only nickel corrosion compounds. Increasing the nickel content in the alloy reta...
TL;DR: In this paper, the effects of MgO and CaO on the hot corrosion behavior of an iron based superalloy, Superfer 800H (equivalent to Incoloy 800) has been investigated using an aggressive environment of Na2SO4-60 wt-%V2O at 900°C for up to 50 cycles.
Abstract: Molten vanadate induced hot corrosion is a serious problem in power plants using residual fuel oil. In this investigation the effects of MgO and CaO on the hot corrosion behaviour of an iron based superalloy, Superfer 800H (equivalent to Incoloy 800) has been investigated using an aggressive environment of Na2SO4-60 wt-%V2O at 900°C for up to 50 cycles. Weight change has been plotted with respect to time to establish the corrosion kinetics. Corrosion products were analysed by SEM, X-ray diffraction, and electron probe microanalysis (EPMA). X-ray diffraction identified the presence of the phases FeV2O4, Fe2O3, FeS, NiO, and Cr2O3, together with Mg3V2O8 in the case of MgO coated specimens and Ca3V2O8 in the case of CaO coated specimens. These latter phases remain solid at 900°C, explaining the inhibiting behaviour of CaO and MgO. The presence of various oxides and spinels was identified by EPMA. It is concluded that MgO and CaO injected onto hot section surfaces can be used to counteract hot corros...
TL;DR: In this article, a potentiostatic weight loss technique was used to compare the corrosion rates of Weldox 700 high strength low alloy steel exposed to both natural and sterile sea water at potentials ranging from the free corrosion condition to - 1000 mV (SCE).
Abstract: A potentiostatic weight loss technique has been used to compare the corrosion rates of Weldox 700 high strength low alloy steel exposed to both natural and sterile sea water at potentials ranging from the free corrosion condition to - 1000 mV (SCE). Anodic polarisation curves with Tafel constants of 54 and 64 mV per decade were fitted to the data and the minimum levels of protection required to limit the corrosion rate to 0·001 mm per year were found to be - 770 and - 790 mV (SCE) in natural and sterile sea water, respectively. Lower corrosion rates occurred in filtered natural sea water than in sterile sea water but the highest rates were recorded on specimens ex posed to a seabed sediment. The reasons for this behaviour are discussed in terms of the biofilms and the numbers of sulphate reducing bacteria present on the surfaces.
TL;DR: In this article, a low nickel copper alloy commonly used in the plumbing/drainage pipelines on ships was investigated under slow strain rate conditions in air, and in solution containing 3·5%NaCl + 10%MgCl2, with and without 1% ammonia.
Abstract: A low nickel copper alloy commonly used in the plumbing/drainage pipelines on ships was investigated under slow strain rate conditions in air, and in solution containing 3·5%NaCl + 10%MgCl2, with and without 1% ammonia. The tests were conducted at ambient temperature (28 ± 1°C) at strain rates corresponding to a crosshead speed of 5·76 × 10-5cm min-1, without a passivation current. The results obtained did not show any significant deterioration in the mechanical properties of the alloy in the tests conducted in air or in solution without ammonia. However, with the introduction of 1% ammonia, a reduction in the material strength and a change in the mode of failure were observed. This paper discusses the results obtained in the present investigation and in particular the load bearing capacity of the material and the modes of failure in Cu–Ni alloys exposed to sea water.
TL;DR: In this paper, the relationship between the concentration of TiO2 in the slags and the corrosion rate of the refractories, the effects of slag basicity (CaO/SiO2), and the effect of the temperature of the molten bath was examined.
Abstract: Interactions between smelting reduction slags containing titania (0·2-20 wt-%TiO2) and MgO-C refractories have been investigated by stationary immersion and rotary immersion at temperatures of 1773-1923 K. The relationship between the concentration of TiO2 in the slag and the corrosion rate of the refractories, the effects of slag basicity (CaO/SiO2), and the effect of the temperature of the molten bath on the corrosion rate were examined. Increasing the TiO2 concentration in the slag caused an increase in the corrosion rate of the MgO-C refractories. The corrosion rate also increased when the temperature was increased. Increasing the basicity of the acid slag decreased the corrosion rate, but this effect was not evident when the basicity of slag exceeded 1·0. The corrosion mechanism of MgO-C refractories in smelting reduction melts containing titania involves the oxidation of graphitic carbon by TiO2 and the formation of a deterioration layer containing Ti and TiC, together with the reaction of m...
TL;DR: In this article, the pore resistance of anodised aluminium surfaces has been studied using electrochemical impedance spectroscopy (EIS) in aqueous KCl and K2SO4 solutions.
Abstract: Both electroless nickel coated and chromated surfaces of magnesium alloy AZ 31 and hydrothermally sealed anodised surfaces of unalloyed aluminium Al-2S and aluminium alloy 6061 have been prepared and the corrosion behaviour of these surfaces in aqueous K Cl and K2SO4 solutions has been studied using electrochemical impedance spectroscopy (EIS). The effect of the concentration of hypophosphite in the plating bath used for electroless plating on the Ni-P layers formed and their corrosion behaviour has also been studied. The EIS studies have shown that the diffusion of ionic species is less for yellow chromated surfaces of magnesium alloy than for black chromated ones. In the case of anodised aluminium surfaces, impedance values are much higher in KCl than in K2SO4 solutions. The effect of anodising time on pore resistance R po and barrier capacitance Cb has also been studied. Data from EIS indicate that the pore resistance of aluminium alloys A1-2S and AA 6061 attains a saturation value after anodis...
TL;DR: In this article, anodic polarisation measurements have been carried out on type 316L stainless steel (as a reference material) and on alloys 33 and 24 in a simulated flue gas desulphurization environment in order to assess the localised corrosion resistance.
Abstract: Potentiodynamic anodic polarisation measurements have been carried out on type 316L stainless steel (as a reference material) and on alloys 33 and 24 in a simulated flue gas desulphurisation environment in order to assess the localised corrosion resistance. The results showed that the pitting corrosion resistance was higher in the case of alloys 33 and 24 than in the reference material owing to the higher contents of nitrogen, chromium, and molybdenum. An accelerated leaching study conducted on the alloys 33 and 24 showed only minor tendencies for the leaching of metal ions at various impressed potentials. Observations by SEM confirmed the lower tendency towards pitting of the alloys 33 and 24.
TL;DR: In this article, seven homologous imidazoline inhibitors, the derivatives of cyclopentylic and cyclohexylonaphthenic acids, have been synthesized.
Abstract: Seven homologous imidazoline inhibitors, the derivatives of cyclopentylic and cyclohexylonaphthenic acids, have been synthesised. The effectiveness of these inhibitors for St3S carbon steel and 1H18N9T austenitic stainless steel was tested using the impedance method in 2 wt-% sodium chloride solution in the presence of a hydrocarbon phase. The solution was saturated with hydrogen sulphide. It was found that the inhibitors and their mix tures displayed high inhibition efficiencies, reaching 93% for carbon steel and 94% for the austenitic steel. Inhibitors with the shortest hydrocarbon side chains on the imidazoline ring were found to offer the lowest level of protection, the inhibition efficiency increasing with the length of the side chain. The capacitance measured on the surface decreased linearly as the coverage of the steel surface by inhibitor increased. The results of impedance measurements with commercial inhibitors have confirmed the conclusions from the tests on the pure chemical species.
TL;DR: In this article, the semiconductor properties, electronic structure and reduction susceptibility of passive films on AISI type 304 stainless steel in dilute sulphuric acid solutions have been studied by electrochemical impedance spectroscopy measurements, Mott-Schottky analysis and the photoelectrochemical technique.
Abstract: The semiconductor properties, electronic structure and reduction susceptibility of passive films on AISI type 304 stainless steel in dilute sulphuric acid solutions have been studied by electrochemical impedance spectroscopy measurements, Mott-Schottky analysis and the photoelectrochemical technique. The passive film shows features of an amorphous or highly disordered n type semiconductor. The donor level is in the range of 1026-1027 m-3 and increases with the amplitude of ac potential. The passive film thickness increases linearly with the amplitude of the applied ac potential. The reduction susceptibility of the passive film is also decreased with the amplitude of the applied ac. The photoelectrochemical measurements also indicate that the passive film is n type semiconductor and the photcurrent is decreased after ac modulation. It might be related to the surface chromium accumulation.
TL;DR: In this paper, various corrosion inhibitors, including 1-hydrox y ethylene-1,1 diphosphonic acid (HEDP), sodium molybdate, and zinc ions with various concentrations of chloride ion, were added to an aqueous corrosive medium, and the corrosion rate of the carbon steel was measured at various temperatures.
Abstract: Various corrosion inhibitors, including: 1-hydrox y ethylene-1,1 diphosphonic acid (HEDP), sodium molybdate, and zinc ions with various concentrations of chloride ion, were added to an aqueous corrosive medium, and the corrosion rate of the carbon steel was measured at various temperatures. It is shown that the corrosion rate is increased when the temperature or chloride ion concentration is enhanced, while if the concentration of HEDP or molybdate is increased, the corrosion rate is lowered. Furthermore, it is observed that in presence of more than 1200 ppm of the chloride ion and temperatures greater than or equal to 42·5°C the combination of HEDP, molybdate and zinc cannot control the corrosion in a cooling water system. Ultimately, a formulation consisting of HEDP, 2-phosphono butane-1, 2,4 tricarbox ylic acid, tolyltriazole, zinc, and polymeric compounds has been developed and tested in an industrial cooling water unit. Results have shown that the corrosion rate may be lowered to less than 25...
TL;DR: In this paper, further tests have been conducted on the same alloy to study its mechanical/corrosion behaviour on exposure to an aqueous solution of ammonia in comparison with exposure to a similar solution of ammonium containing 3·5%NaCl + 10%MgCl2.
Abstract: The test results from an earlier investigation by the author on the mechanical behaviour of a low nickel nickel-copper alloy exposed to a solution of 3·5%NaCl + 10%MgCl2 with and without ammonia indicated that the presence of 1% ammonia alters the failure mode and affects the load bearing capacity of the material. In the present investigation, further tests have been conducted on the same alloy to study its mechanical/corrosion behaviour on exposure to an aqueous solution of ammonia in comparison with exposure to a similar solution of ammonia containing 3·5%NaCl + 10%MgCl2. A constant displacement rate of 9·6 × 10-3 μ m s-1 was used and the concentration of ammonia was maintained at 5%. On exposure to the 5% aqueous ammonia solution, the mechanical properties of the alloy were degraded significantly and the material exhibited a brittle stress corrosion type of failure. However, on exposure to 5% ammonia in the presence of 3·5%NaCl + 10%MgCl2, there was less change in failure mode relative to that ...
TL;DR: In this article, a 3D scanning vibrating electrode technique (3D SVET) was used to investigate the localised corrosion occurring on 2 cm2 exposed areas of flat specimens of electroplated zinc and galvannealed (Zn-Fe alloy coated) 1·2 mm sheet steel and specimens of the same substrates laser welded together.
Abstract: A novel three-dimensional scanning vibrating electrode technique (3D SVET) apparatus is described, which uses a bifunctional probe to record topographical and current density data. This apparatus is used to investigate the localised corrosion occurring on 2 cm2 exposed areas of flat specimens of electroplated zinc and galvannealed (Zn-Fe alloy coated) 1·2 mm sheet steel and specimens of the same substrates laser welded together, freely corroding in near neutral, aerated, aqueous chloride electrolyte. On flat galvannealed (IZ) specimens anodic events are highly localised and occur at random over the exposed specimen surface during a 24 h immersion period. This reflects the progressive dezincification of zinc rich areas of the iron zinc intermetallic coating. By contrast on flat electroplated zinc (EZ) specimens anodic activity is localised but corrosion initiates at a single anodic centre, eventually spreading out to form a scar on the metallic surface. This concentration of anodic activity on the...
TL;DR: In this article, Potentiodynamic polarisation curves have been used to evaluate the corrosion performance of 1008 carbon steel coated with hybrid (inorganic-organic) and mixed oxide coating systems deposited by dip coating.
Abstract: Potentiodynamic polarisation curves have been used to evaluate the corrosion performance of 1008 carbon steel coated with hybrid (inorganic-organic) and mixed oxide coating systems deposited by dip coating. Several coatings have been prepared by the sol-gel method, using metallic alkox ides, such as tetraethylorthosilicate, aluminium isopropoxide, and zirconium propoxide, and polymers like allyl methacrylate (AMA) and polymethylmethacrylate (PMMA), together with zirconium dioxide (ZrO2) and silicon and aluminium oxides (SiO3-Al2O3). The aqueous test solutions included hydrochloric acid (HCl), sodium chloride (NaCl), and sulphuric acid (H 2SO4) at various concentrations (0·1, 0·5, and 1M). Scanning electron microscopy was used to examine the coatings following testing. The results have shown that SiO2-Al2O3 based coatings are not beneficial for corrosion protection in HCl, but are of value in the other aqueous media. In 1·0M HCl, the best protection was offered by a hybrid SiO2-ZrO2-poly(methylmet...
Abstract: Cyclic dip testing of coil coated architectural claddings was carried out in order to understand the mechanisms of cut edge corrosion. Thus, a number of nominally identical materials from the same manufacturer, but with varying steel thickness (and, hence, zinc to steel area ratios at the cut edge) were examined. The degree of disbondment of the organic coating from the cut edge was measured after 1000 h. For a constant thickness of zinc coating, the results demonstrate a linear relationship between the degree of coating disbondment and the thickness of the steel substrate. Further, the trend line showed a positive amount of disbondment when ex trapolated to zero thickness of steel. It is concluded that the cathodic disbondment mechanism plays an important role in the initiation of organic coating failure at the cut edge. However, the kinetics of cut edge disbondment is dominated by the anodic undermining mechanism.
TL;DR: The synergistic inhibition of aluminium bronze corrosion by 4-phenyl semicarbazide hydrochloride (PSC) and the iodide ion in HCl of pH (1·8-2) at 60°C has been assessed by polarisation studies, Tafel plots, X-ray photoelectron spectroscopy and Auger electron spectrography as discussed by the authors.
Abstract: The synergistic inhibition of aluminium bronze corrosion by 4-phenyl semicarbazide hydrochloride (PSC) and the iodide ion in HCl of pH (1·8-2) at 60°C has been assessed by polarisation studies, Tafel plots, X-ray photoelectron spectroscopy and Auger electron spectroscopy. The addition of 0·01M KI to 0·01M PSC improved the inhibition efficiency from 86 to 94% owing to the formation of a CuI-PSC complex which is more compact, protective and hard than the film formed in the absence of iodide. The inner layer of this protective film contains a small amount of aluminium oxide, which increases the protective nature of the film and retards the dissolution of the underlying aluminium bronze.
TL;DR: In this article, the effects of erosion on the corrosion of two types of stainless steel in aqueous 0·5M NaCl and 1m NaCl environments at ambient temperature have been studied using a modified rotating cylinder electrode system.
Abstract: The effects of erosion on the corrosion of two types of stainless steel in aqueous 0·5M NaCl and 1M NaCl environments at ambient temperature have been studied using a modified rotating cylinder electrode system. Erosion by silica particles greatly increased the passive current density for both ferritic type 430 and austenitic type 316 stainless steels. It is suggested that two factors were largely responsible for the observed effects. The impact of the eroding silica particles on the specimen surface destroyed the passive film and removed corrosion products from the specimen surface; and impact with the fast moving silica particles generated numerous microplastic deformation sites on the metal surface which were activated owing to the presence of residual stress, dislocations and defects, etc., and the emission of low energy electrons.
TL;DR: Results based on 16S rRNA gene sequence similarity suggest that these aerobic or facultative bacteria could be a new species in this kind of environment.
Abstract: A study of microbiologically induced corrosion has been conducted on X52 pipeline steel using bioelements which were located in a bioprobe located at the inner surface of a sea water pipeline and exposed for 60 days. Severely attacked surfaces with pits of various diameters and depths and a great deal of metal loss were observed after removing the biofilm that had deposited on the bioelement surfaces. This behaviour was not expected under the normal operating conditions of the pipeline. Pit depths were measured and a depth distribution curve was obtained. Different aerobic or facultative bacteria types were cultured from the biofilm removed from the X52 steel bioelement surface while a negative growth in the anaerobic bacteria culture was observed. The morphological and chemical characteristics of the aerobic bacteria were determined and results based on 16S rRNA gene sequence similarity suggest that these aerobic or facultative bacteria could be a new species in this kind of environment.