Chemical corrosion of E-glass fibres in neutral phosphate solutions

Following local reports of failure of glass reinforced plastic (GRP) tanks used for the storage of ammonium orthophosphate fertilizer, the effect of phosphate solutions on the strength retention of E-glass fibre was investigated. Although solutions (1 to 5 mol dm^–3) of mineral acids are known to corrode E-glass fibre, phosphoric acid solution (3 mol dm^–3; pH 1.55) is essentially inert and strength retention of the glass fibre after 15 days exposure is the same as the water control. However, as the pH is raised strength retention is diminished and a minimum is observed around pH 7 to 8. A chemical explanation of this behaviour is put forward in terms of leaching and complex formation with calcium and magnesium ions. Although not nearly as corrosive as other agents, evidence suggests that phosphate solutions do corrode E-glass fibre and this should be borne in mind when GRP materials are used in such chemical environments.     

Self-sensing E-glass fibres

The primary aims of this study were to demonstrate that conventional reinforcing E-glass fibres could be converted to act as waveguides. This was achieved by selecting and applying appropriate cladding material onto the glass fibre bundle. Three classes of cladding materials were evaluated: epoxy, polyurethane and sol–gel. The light transmission characteristics through the E-glass waveguides was evaluated and compared. The epoxy and polyurethane cladding were found to be superior compared to the sol–gel coated fibres in terms of the quality of the coating and the light transmission intensity over specified lengths. The effect of fibre-end preparation on the light transmission characteristic was also investigated. The feasibility of conducting in situ tensile tests where the light transmission intensity was passed through the E-glass fibres was demonstrated successfully. This in situ technique was capable of highlighting differences in the macroscopic tensile failure modes obtained using the various cladding materials.     

Strength loss in E-glass fibres after exposure to hydrochloric,hydrobromic and hydriodic acids

The corrosion of E-glass fibres by hydrochloric, hydrobromic, and hydriodic acids has been investigated by measuring the loss of mechanical strength of the fibres following immersion in solutions of the acids. Corrosion is greatest in hydrochloric acid and least in hydriodic acid. Curves of percentage strength retention against concentration show well-defined minima for hydrochloric and hydrobromic acids, but not for hydriodic acid. This phenomenon has been attributed to complex ion formation by metal ions in the glass with chloride or bromide ions in the corroding solution. Spectroscopic evidence suggests that ferric ions play an important role in the corroding process.     

An acoustic emission study of failure by stress corrosion in bundles of E-glass fibres

Fibre failures in bundles of parallel E-glass fibres loaded from their ends and immersed in aqueous HCl solutions or in water are detected using acoustic emission. In constant load and constant stress tests the times to failure of the fibres and the bundles are accounted for on the basis of a theory which assumes a Weibull distribution of initial strengths, and that the velocity (v) of subcritical stress-corrosion cracks in the fibres depends on the stress intensity (K _l) according to a power law (VK _l ⁿ ). The crack growth parameter (n) is measured by three methods, and its variation with acid strength is correlated with other corrosion studies. The stress corrosion measurements also allow a determination of the Weibull modulus of the fibres.     

盐酸介质中几种表面活性剂对钢的缓蚀作用

采用失重法和电化学方法研究了在HCl介质中阳离子表面活性剂十六烷基三甲基溴化铵(CTAB,C19H42BrN)阴离子表面活性剂十二烷基磺酸钠(DSASS,C12H25SO3Na)及非离子表面活性剂聚乙二醇辛基苯基醚(OP)对钢的缓蚀作用.应用吸附理论讨论缓蚀作用产生的原因.结果表明,在同一浓度下,三种表面活性剂对钢在HCl介质中的缓蚀效率的顺序如下CTAB＞OP＞DSASS.     

Tributylamine as corrosion inhibitor for mild steel in hydrochloric acid

The corrosion inhibition of mild steel in 2 M hydrochloric acid solution by tributylamine has been investigated using the impedance technique. Tributylamine was studied in concentrations from 5 × 10^–4 M to 1 M at a temperature of 298 K. The inhibitor mechanism was treated as a substitutional adsorption process according to Flory-Huggins, Dhar-Flory-Huggins and Bockris-Swinkels isotherms. The best approach was obtained using the latter. A structural parameter, the projected molecular area of tributylamine, was calculated to elucidate inhibitor orientation in the adsorption process.     

Effects of alcohol-based inhibitors on corrosion of mild steel in hydrochloric acid

The inhibition efficiencies of Octyl alcohol (OCAL) and propargyl alcohol (PRAL) on the corrosion of mild steel in 15% commercial hydrochloric acid have been evaluated by mass loss method, electrochemical techniques and surface analysis techniques with 0–1% inhibitor concentration at 30 °C and 105 °C. Both OCAL and PRAL are excellent inhibitors for the above-mentioned system. OCAL gives 87% and 82% inhibition efficiencies at 30 °C and 105 °C, respectively, for 1% inhibitor concentration whereas PRAL gives 100% and 99% efficiencies at 30 °C and 105 °C, respectively, for 0.6% inhibitor concentration. Polarization studies confirm that OCAL and PRAL are mixed type inhibitors. OCAL and PRAL obey Temkin's adsorption isotherm at both the temperatures. UV-reflectance, FT-IR and SEM studies confirm that the surface of mild steel is not affected at the maximum concentration of OCAL and PRAL.     

The inhibition of mild steel corrosion in hydrochloric acid media by two Schiff base compounds

Schiff bases of 2-({-1-methyl-3-[(2-sulfanylphenyl)imino]butylidene}-amino)-1-benzenethiol and 2-({-1,2-diphenyl-2-[(2-sulfanylphenyl)imino]ethylidene}amino)-1-benzenthiol are investigated as corrosion inhibitors in acid solution. Polarization, electrochemical impedance spectroscopy, and weight loss measurements were performed on mild steel in 15% HCl with and without the inhibitors. A significant decrease in the corrosion rate of mild steel was observed in the presence of investigated inhibitors. Polarization curves indicate that both compounds are mixed inhibitors, affecting both cathodic and anodic corrosion currents. The adsorption of inhibitors on mild steel surface in 15% HCl was found to follow Langmuir adsorption isotherm. Thermodynamic adsorption parameters (K _ads, ∆G _ads) of studied Schiff bases were calculated using the Langmuir adsorption isotherm. Activation parameters of the corrosion process such as activation energies, E _a, activation enthalpies, ∆H*, and activation entropies, ∆S*, were calculated by the obtained corrosion currents at different temperatures.     

块体纳米晶工业纯铁在盐酸溶液中的电化学腐蚀行为

通过静态失重试验,动电位极化曲线,电化学阻抗谱(EIS)实验,研究了块体纳米工业纯铁(BNIPI)和粗晶工业纯铁棒(CGPIR)在室温1mol/l盐酸溶液中的腐蚀行为.结果表明,BNIPI与CGPIR相比,开路腐蚀电位Ecorr正向移动114mV,平均腐蚀速度和腐蚀电流Icorr变小,极化电阻Rp增大为1.58倍.BNIPI抗盐酸的腐蚀能力与CGPIR相比,不但没有下降,相反有所增强.使用扫描电子显微镜(SEM)对静态腐蚀失重试样的形貌进行了观察,显示BNIPI上几乎没有点蚀坑出现.     

Strength loss in E-glass fibres after exposure to organic acids

The corrosion of E-glass fibres has been investigated in aqueous solutions of selected organic acids. Although most organic acids have very little corrosive effect, oxalic acid and mesoxalic acid (2-oxopropanedioic acid) are extremely corrosive. The mechanism of the corrosion process appears to be related to three factors: relatively high acidic strength, formation of an insoluble calcium salt, and an ability to form stable complexes with cations present in the glass. This corrosion is extremely important when glass fibre composites are used in conditions where oxidative breakdown (e.g. by electric fields or ultraviolet radiation) of the resin material is likely to occur, as the two most corrosive organic acids are likely breakdown products.     

Inhibition effect of potassium iodide on corrosion of stainless steel in hydrochloric acid solution

The inhibition effect of potassium iodide on the corrosion of stainless steel has been examined using weight loss and electrochemical measurements. Potassium iodide was found to be an excellent inhibitor for stainless steel types 316, 430 and 440 (efficiency more than 95%), and moderate for type 304. The corrosion rates in 1m HCl and in presence of potassium iodide fit an Arrhenius equation. The presence of potassium iodide lowered both the activation energy and the rate of reaction. Polarization measurements indicated that potassium iodide acts as an anodic inhibitor particularly at higher concentrations and as a cathodic inhibitor at lower concentrations. The synergistic effect of potassium iodide on the inhibitive efficiency of the organic substances was studied.     

The inhibition of mild steel corrosion in 1 M hydrochloric acid solutions by triazole derivative

The title compound 1-(4,5-dihydro-3-phenylpyridine-1-yl)-2-(1H-1,2,4-triazole-1-yl)ethyl ketone (DTE) was synthesized and its inhibiting action on the corrosion of mild steel in 1 M hydrochloric acid solutions was investigated by means of weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electronic microscope (SEM). Results obtained revealed that DTE performed excellently as a corrosion inhibitor for mild steel in 1 M hydrochloric acid media and its efficiency attains more than 90.9% at 1.0 × 10^− 3 M at 298 K. Polarization curves indicated that the inhibitor behave mainly as mixed-type inhibitor. EIS showed that the charge transfer controls the corrosion process in the uninhibited and inhibited solutions. Adsorption of the inhibitor on the mild steel surface followed Langmuir adsorption isotherm. And the values of the free energy of adsorption ΔG_ads indicated that the adsorption of DTE molecule was a spontaneous process and was typical of chemisorption.     

Intramolecular synergistic effect of glutamic acid, cysteine and glycine against copper corrosion in hydrochloric acid solution

The corrosion protection of copper by glutamic acid, cysteine, glycine and their derivative (glutathione) in 0.5 M hydrochloric acid solution has been studied by the electrochemical impedance spectroscopy and cyclic voltammetry. The inhibition efficiency of the organic inhibitors on copper corrosion increases in the order: glutathione > cysteine > cysteine + glutamic acid + glycine > glutamic acid > glycine. Maximum inhibition efficiency for cysteine reaches about 92.9% at 15 mM concentration level. The glutathione can give 96.4% inhibition efficiency at a concentration of 10 mM. The molecular structure parameters were obtained by PM3 (Parametric Method 3) semi-empirical calculation. The intramolecular synergistic effect of glutamic acid, cysteine and glycine moieties in glutathione is attributed to the lower energy of the lowest unoccupied molecular orbital (E_LUMO) level and to the excess hetero-atom adsorption centers and the bigger coverage on the copper surface.     

The environmental stress corrosion cracking of glass fibre-reinforced laminates and single E-glass filaments

The environmental stress corrosion cracking of epoxy/glass fibre crossply, unidirectional coupons and single E-glass filaments have been compared. At initial applied strains > 0.15% the resin does not protect the fibres as shown by their equivalent failure times. The failure occurs in the environment and planar fractures occur because of the localized stress in the load bearing plies adjacent to a transverse crack in the 90° ply of the 0°/ 90°/0° coupons. These transverse cracks result from stress corrosion of the glass/resin interface, which leads to a reduction of the transverse cracking strain. At applied strains < 0.15% fracture occurs within the unexposed half of the coupons and is thought to be caused by rapid transport of glass corrosion products where they crystallize within the coupon. This phenomenon is also responsible for the progressive transverse cracking that occurs in both the 0° and 90° plies of the unimmersed half of the crossply coupon under zero load.     

Electrochemical impedance study on the corrosion of Al-Pure in hydrochloric acid solution using Schiff bases

The inhibition effect of newly synthesized Schiff bases N-benzylidene benzylamine (A) and benzenemethanamine-α-methyl-N-(phenylmethylene) (B) on the corrosion behaviour of Al-Pure in 1·0 M HCl was studied using galvanostatic polarization and electrochemical impedance spectroscopy (EIS) and adsorption studies. The effects of inhibitor concentration, temperature and surface coverage are investigated. The effect of inhibitor concentration and other parameters are evaluated for different inhibitor concentrations and the probable mechanism was also proposed. The results show that (A) and (B) possess excellent inhibiting effect for the corrosion of Al-Pure and the inhibitors act as mixed type inhibitors. The inhibitors do not affect the mechanism of the electrode processes and inhibit corrosion by blocking the reaction sites. The high inhibition efficiency of (A) and (B) were due to the adsorption of inhibitor molecules on the metal surface. The decrease of surface area available for electrode reactions to take place is due to the formation of a protective film. Activation energy and free energy of adsorption have been calculated.