ISSN 2305-6894

2018, Vol. 7, Issue 3 (pp. 271-459)

Prev. issue<- -> Next issue

Triazoles as a class of multifunctional corrosion inhibitors. A review. Part I. 1,2,3-Benzotriazole and its derivatives. Copper, zinc and their alloys

  • Yu.I. Kuznetsov
A. N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119071 Russian Federation

Abstract: This article presents an overview of the studies (2003–2018) on the adsorption of 1,2,3-benzotriazole (BTA) and its derivatives on copper, zinc and some of their alloys from aqueous solutions, and their corrosion inhibition capability in neutral and acidic media. It examines the effect of these organic corrosion inhibitors (CIs) on the formation of surface layers, their composition and the effectiveness of their protective action that were investigated by corrosion, electrochemical and other physicochemical methods. Considerable attention has been given to BTA itself, the wide range of corrosive media in which it can be an effective CI, an analysis of the reasons for its successful application in the practice of anticorrosion protection of copper and its alloys, as well as the new prospects of its usage and increasing its inhibition efficiency. At the same time, the drawbacks of BTA as a CI, including the sharp decrease in protective properties, up to their complete loss, in the presence of even small concentrations of H2S and sulfide ions and the relatively low efficiency in acid solutions were noted. The inhibition of corrosion of zinc and copper–zinc alloys by BTA has been discussed. It has been shown that the protection is based on the formation of sparingly soluble complexes of copper and zinc with BTA. Examples of improving the effectiveness of their protection with mixed CIs are given. The review notes the almost complete absence of studies of BTA derivatives for the protection of Zn, which could also be very useful for improving the corrosion protection not only of zinc but also galvanized steel.

Int. J. Corros. Scale Inhib., , 3, 271-307 PDF (824 K)
doi: 10.17675/2305-6894-2018-7-3-1

The effect of triazoloazepine bromide with biocidal activity on microbial copper corrosion

  • , , , and
1 Chernihiv National T.G. Shevchenko Pedagogical University, 53 Hetmana Polubotka str., 14013 Chernihiv, Ukraine
2 National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, 37 Peremohy Ave, Kyiv, 03056 Ukraine

Abstract: The study deals with the effect of triazoloazepine bromide with biocidal activity against sulfate-reducing bacteria on microbial copper corrosion in neutral water–salt Postgate “B” medium with the enrichment culture of bacteria, isolated from the biofilm, formed on the metal surfaces of sewage treatment facilities. It has been established that the studied substance also inhibits the growth of iron-reducing bacteria, denitrifying bacteria and ammonifying bacteria, which ensure the stable growth of the most numerous and aggressive constituent of the enrichment culture – sulfate-reducing bacteria. It has been demonstrated that triazoloazepine bromide increases the redox potential of the corrosive medium by up to 170 mV. This enables the change of enzymatic reactions direction and considerable inhibition of sulfate-reducing activity of the enrichment culture bacteria. The morphology of the copper coupons surface after the exposure to the corrosive medium with bacterial sulfate-reduction has been examined. It has been defined that without triazoloazepine bromide the biofilm is a chaotic accumulation of bacteria in the polymeric matrix. In the presence of triazoloazepine bromide, only individual bacteria can be observed in the corrosive medium on the surface of the biofilm, which has a loose structure. It has been estimated that triazoloazepine bromide decreases the rate of microbial copper corrosion by a factor of 11.7.

Int. J. Corros. Scale Inhib., , 3, 308-317 PDF (764 K)
doi: 10.17675/2305-6894-2018-7-3-2

The inhibition of CO2 corrosion of L360 mild steel in 3.5% NaCl solution by imidazoline derivatives

  • , , , and
1 Department of Pure & Industrial Chemistry, Abia State University, Uturu, Abia State, Nigeria
2 Corrosion and Electrochemistry Research Group, Department of Pure & Applied Chemistry, University of Calabar, Calabar, Nigeria
3 SINOPEC Research Institute of Safety Engineering, 218, Yan'an 3rd RD, Qingdao, P.R. China, 266071

Abstract: [2-(2-Henicos-10-enyl-4,5-dihydro-imidazol-1-yl)-ethyl]-methylamine (HDM), 2-(2-henicos-10-enyl-4,5-dihydro-imidazol-1-yl)-ethanol (HDE) and 2-henicos-10-enyl-4,5-dihydro-1H-imidazole (HDI) were synthesized using the solvent free microwave assisted organic synthesis method and characterized by FT-IR. The corrosion inhibition properties of these compounds on mild steel L360 in 3.5% NaCl solution were investigated by weight loss, potentiodynamic polarization, electrochemical impedance and scanning electron microscopic techniques. The synthesized inhibitors were tested at 60°C and 80°C with concentrations of 10, 50, 100, 200 and 300 ppm, respectively. The results from the study showed that the inhibition efficiency increased with increase in the concentration of the inhibitor to a maximum and decreased with rise in temperature. An adherent layer of inhibitor molecules on the surface is proposed to account for their inhibitive action in which the organic molecules adsorb on the active anodic and cathodic sites following Langmuir isotherm. The effectiveness of these inhibitors has been correlated to their chemical structures and were in the order of HDM > HDE > HDI. The values of activation energy, free energy of adsorption and heat of adsorption were also calculated to elaborate the mechanism of corrosion inhibition. The values obtained from the heat of adsorption (Qads) for the three inhibitors studied (HDM, HDE and HDI) are –58.53 kJ mol–1, –103.27 kJ mol–1 and –133.67 kJ mol–1, respectively. These negative values indicate that the adsorption of the inhibitors on the mild steel is exothermic signifying physical adsorption. The potentiodynamic polarization data show that the compounds studied are mixed type inhibitors. The surface characteristics of inhibited and uninhibited metal samples were investigated by scanning electron microscopy (SEM).

Int. J. Corros. Scale Inhib., , 3, 318-330 PDF (615 K)
doi: 10.17675/2305-6894-2018-7-3-3

Protective ability of volatile inhibitors of IFKhAN series in atmospheric corrosion of brass and copper at high concentrations of CO2, NH3 and H2S in air

  • , , , , and
1 All-Russian Scientific Research Institute of Use of Machinery and Oil Products, Novo-Rubezhnyi per., 28, Tambov, 392022, Russian Federation
2 Tambov State Technical University, Sovetskaya str., 106, Tambov, 392000, Russian Federation
3 Derzhavin State University, ul. Internatsyonalnaya str., 33, Tambov, 392000, Russian Federation

Abstract: The protective efficacy of volatile inhibitors (VCI) IFKhAN-8 (an amino alcohol), IFHAN-112 (a mixture inhibitor based on benzotriazole), IFKhAN-114 (a non-equimolar mixture of a polyamine and a weak organic acid) and IFKhAN-118 (a dimethyl¬benzylamine salt) was studied in atmospheric corrosion of M2 copper (99.7 wt.%) and L62 two-phase brass (22.5 wt.% Zn and 67.7 wt% Cu) in the presence of corrosion stimulators (CS): CO2 (0.2–0.6 vol.%), NH3 (20–60 mg/m3) and H2S (10–30 mg/m3), either separately or in combination. In an uninhibited atmosphere with 0.6 vol.% CO2 + 60 mg/m3 NH3 (three times higher than the normally permissible CS concentrations) with a relative humidity of 100%, corrosion of copper and brass has a pronounced local character. In addition, there is a darkening of a significant fraction of the surface of metals (CuO film). The protective efficiency (Z%) of IFKhAN-112, IFKhAN-114, and IFKhAN-118 in relation to the total corrosion is 75% (brass) and 85% (Cu); 82% (brass) and 79% (Cu) and 89% (brass) and 85% (Cu), respectively. In the atmosphere with CO2 (0.6 vol.%) + H2S (30 mg/m3) or H2S (30 mg/m3) + NH3 (60 mg/m3) in the presence of IFKhAN-114, Z is 75% (brass, copper). With the other inhibitors being studied in the atmosphere, Z is reduced to 13% or even stimulation of corrosion is observed (CO2 + H2S). In the presence of all the three corrosion stimulators, IFHAN-114 with a protective effect of 96% (brass) and 95% (copper) is again the most effective. This VCI hinders the anodic reaction of ionization of the metals both at the initial stage of exposure in the medium and after 96 hours of exposure. IFHAN-114 inhibits the anodic process in the presence of (NH4)2S or (NH4)2CO3 salts as reaction products of H2S or H2CO3 with NH3 in the solution, which occurs in the surface phase film of moisture. At the same time, this volatile corrosion inhibitor completely prevents local damage to brass and copper under all conditions studied.

Int. J. Corros. Scale Inhib., , 3, 331-339 PDF (501 K)
doi: 10.17675/2305-6894-2018-7-3-4

A new corrosion inhibitor for zinc chamber treatment

  • , , , ,
A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, Moscow, 119071 Russian Federation

Abstract: Thin organic films on metal surfaces can be obtained by adsorption of volatile (vapor-phase) inhibitors (VCI), which, despite the extremely small thickness, provide high corrosion resistance under various atmospheric conditions. However, there is a problem in the practical application of compounds with high vapor pressure, namely, the air-tightness of the joint packaging of VCI and metal products. Infringement of packing air-tightness entails desorption of VCI from the metal surface followed by its corrosion. A fundamentally new opportunity for creating thin films capable of preventing corrosion of metal products in a humid atmosphere during their transportation and inter-operation storage is opened by the treatment of an item or semi-finished product to be protected in hot vapors of non-toxic compounds with low volatility under normal conditions. They evaporate at elevated temperature (t) in the enclosed space of a chamber and strongly adsorbed on the metal to create stable thin films that provide a long-term protective after-effect under atmospheric conditions. This method of vapor-phase protection by chamber corrosion inhibitors has broad prospects of practical application. It has been proven by a complex of accelerated corrosion, electrochemical and optical methods that chamber treatment of zinc with vapors of low volatile corrosion inhibitors at t ≤ 100°C is capable of forming films on zinc surface that possess a prolonged protective after-effect. It has been shown that short-term chamber treatment in the vapor of a new inhibitor, IFKhAN-121, provides effective temporary protection of zinc, both in accelerated tests and when exposed in the industrial atmosphere of Moscow for 1 year.

Int. J. Corros. Scale Inhib., , 3, 340-351 PDF (821 K)
doi: 10.17675/2305-6894-2018-7-3-5

Influence of the nanolayer’ post-treatment on the anticorrosion activity

  • and
1 Óbuda University, Doberdó u. 6., 1034 Budapest, Hungary
2 Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, 1117 Budapest, Hungary
3 PhD School of Materials Sciences and Technologies, Óbuda University, Bécsi út 96/B 1016, Budapest, Hungary
4 Libyan Petroleum Institute, Girgarisg Road Km7, Tripoli, Libya

Abstract: The study of self-assembled molecular layer (SAM) of undecenyl phosphonic acid amphiphilic molecule was in the focus of experiments. This molecule has a double bond at the end of the hydrophobic carbon chain, which does not allow the formation of a very compact SAM layer. The nanolayers were developed on carbon steel surface polished before layer deposition. To increase the compactness of the nanolayer, post-treatments were applied. In one case UV light, in the other case gamma-ray irradiation were used to polymerize the double bonds and form a film with net-like structure on the metal surface. The influence of the SAM layer treatments on the layer structure was followed by monitoring the change in water wettability and by atomic force microscopic (AFM) visualization of the morphological alteration. At the UV treatment the time dependence, at the irradiation the change in the dose were the altered factors. The post-treatments of the self-assembled undecenyl phosphonic acid molecular layer resulted in denser nanolayer structures and the consequence was a significantly improved anticorrosion activity. The change in the roughness parameters (maximum height of the profile, roughness average and the root means square roughness) arisen from the AFM measurements proved the influence of post treatments on the layer structure, which could be correlated with the increase in the anticorrosion ability as it is known that with increasing surface roughness the possibility of pitting corrosion increases. The increased anticorrosion activity is due to the formation of a more effective, compact barrier layer between the nanolayer-covered metal surface and the corrosive environment.

Int. J. Corros. Scale Inhib., , 3, 352-365 PDF (733 K)
doi: 10.17675/2305-6894-2018-7-3-6

A potentiometric study of an H2SO4–H3PO4–H2O system containing Fe(III) and Fe(II) cations

  • ,
A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119071 Russian Federation

Abstract: The potentiometric method was used to study an H2SO4–H3PO4–H2O system (20–95°C) containing Fe(III) and Fe(II) cations. The oxidizing ability of the 2 M H2SO4 + H3PO4 system containing Fe(III) and Fe(II) (1:1) decreases as the molar fraction of H3PO4 increases. The observed effect results from the formation of Fe(III) complexes with phosphate anions that are weaker oxidants than the corresponding hydrate and sulfate complexes. Variation in the total content of the equimolar Fe(III) + Fe(II) mixture (C = 0.01–0.10 M) in 1 M H2SO4 + 1 M H3PO4 nearly does not affect its oxidizing ability. Conversely, an increase in the relative content of Fe(III) in the system considerably increases its oxidative potential. At a fixed concentration of the Fe(III) + Fe(II) mixture in the system (0.04 М), addition of an equimolar mixture of H2SO4 and H3PO4 (up to 6 M) somewhat decreases the oxidizing properties of the system. A probable reason of the efficient protection of low-carbon steel by triazole-based composite inhibitors in H3PO4 or its mixtures with H2SO4 containing Fe(III), in comparison with similar solutions of H2SO4 alone, is that phosphate complexes of Fe(III) are formed in these media. They have lower oxidizing ability in comparison with aqueous and sulfate complexes of Fe(III).

Int. J. Corros. Scale Inhib., , 3, 366-375 PDF (327 K)
doi: 10.17675/2305-6894-2018-7-3-7

Corrosion inhibition of Elektron WE43 magnesium alloy in NaCl solution

  • and
1 A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, Moscow, 119071 Russian Federation
2 Magnesium Innovation Centre MagIC, Helmholtz-Zentrum Geesthacht, Max-Planck Straße 1, Geesthacht, 21502 Germany

Abstract: Magnesium alloys have a wide range of applications but suffer low corrosion resistance. One of the most accessible ways to protect metals from corrosion, which can also be combined with other methods, is the use of corrosion inhibitors. The effect of 1,2,3-benzotriazole, 5-chloro-1,2,3-benzotriazole and sodium dioctyl phosphate on the corrosion of Elektron WE43 magnesium alloy in 0.05 M NaCl solution was studied using polarization and EIS measurements. Azoles do not exhibit the inhibitive action towards the WE43 alloy, but they slightly reduce the barrier effect of the film of corrosion products. Sodium dioctyl phosphate (DOP) is an effective inhibitor due to its anionic nature. It mainly inhibits the anodic dissolution of the alloy and has a slight effect on the cathodic process. DOP enhances the protective effect in time due to improvement of protective films. An increase in DOP concentration depresses the anodic dissolution of the alloy as well as the local depassivation, which is characterized by a displacement of the pitting potential in the positive direction. Scanning vibrating electrode technique (SVET) measurements confirmed the effectiveness of DOP as a corrosion inhibitor for Electron WE43 alloy.

Int. J. Corros. Scale Inhib., , 3, 376-389 PDF (720 K)
doi: 10.17675/2305-6894-2018-7-3-8

The inhibition effect of sodium tetraborate on the corrosion of steel in KOH media

Department of Chemistry, Faculty of Science, Ankara University, Ankara, Turkey

Abstract: In this study, the inhibition effect of sodium tetraborate (Na2B4O7·10H2O) on the corrosion of steel has been investigated in 3% and 5% KOH media. Corrosion parameters have been determined using Tafel extrapolation and impedance spectroscopy methods by the addition of 1% – 7% Na2B4O7 into two concentrations of KOH solutions. It has been found that the inhibition efficiency of Na2B4O7 in both KOH media increases in 1% – 4% concentration range whereas it decreases in 5% – 7% concentration range. However, corrosion rates are less than when the corrosion media does not contain the inhibitor. The effect of temperature on the corrosion rate of steel and the inhibition effect of Na2B4O7 concentration have also been investigated by carrying out each experiment at four different temperatures, i.e., 25°C, 40°C, 55°C and 70°C. Corrosion rates have been observed to increase with temperature and KOH concentration both in 3% and 5% media. Na2B4O7 is an effective inhibitor at low temperature for steel. According to scanning electron micrograph (SEM) images obtained by adding 4% Na2B4O7 into both KOH media for bare steel and steel, pitting corrosion occurs on the metal surface. Experimental results support SEM images. H2 flows in 3% and 5% KOH media have been investigated using gasometric measurement depending on the concentration of Na2B4O7 by a flowmeter and it has been observed that H2 flow rate decreases in 1% – 4% inhibitor concentration range for both KOH whereas it remains fixed in 5% – 7% concentration range especially in 5% KOH solution. This finding is consistent with the values found by determining corrosion rates and inhibition efficiencies.

Int. J. Corros. Scale Inhib., , 3, 390-408 PDF (1 266 K)
doi: 10.17675/2305-6894-2018-7-3-9

Corrosion of iron in 1 M HCl solutions containing benzhydrazide derivatives with two terminal adsorption groups as additives

  • , and
1 Southern Federal University, ul. Zorge 7, Rostov-on-Don, 344090 Russian Federation
2 Don State Technical University, Gagarin sq. 1, Rostov-on-Don, 344000 Russian Federation

Abstract: The rate of corrosion of iron in 1 M HCl at different concentrations C of benzhydrazide additives was determined in a wide range of solution temperatures. The values of corrosion inhibition coefficients K under the conditions studied are insignificant and in some cases practically do not depend on the inhibitor concentration in the solution. An explanation is provided for these facts on the basis of the influence on these compounds of the structure and nature of the two adsorption groups in the molecule of the compounds studied and allowance for their possible vertical position during the adsorption on the surface of the iron sample. The effective activation energies of Fe corrosion in 1 M HCl inhibited by benzhydrazide derivatives were determined. They were found to be independent on the inhibitor concentration. Based on the specificity of the structure of the investigated compounds (two adsorption centers) and the possible formation of a solution layer saturated with fragments of adsorbed inhibitors, the independence of activation energy W on inhibitor concentration with increasing inhibitor concentration is explained. The values of W correspond to the mixed diffusion-kinetic control of Fe dissolution under the conditions studied and are close to the values of W reported in literature for the dissolution of Fe in HCl.

Int. J. Corros. Scale Inhib., , 3, 409-417 PDF (403 K)
doi: 10.17675/2305-6894-2018-7-3-10

Performance of a novel fluorescent-tagged polyacrylate at a cooling tower test facility: a bench-scale and industrial-scale evaluation

  • , , , , , and
1 PJSC “Fine Chemicals R&D Centre”, Krasnobogatyrskaya, 42, str.1, 107258 Moscow, Russian Federation
2 Mendeleev University of Chemical Technology of Russia, Miusskaya sq. 9, 125047 Moscow, Russian Federation
3 EMEC Russia LLC, 123423, Narodnogo Opolchenia street, 34 bld.3 office 214, Moscow, Russian Federation
4 EMEC SRL, Via Donatori di Sangue, 1 - 02100 Rieti, Italy

Abstract: The ability of fluorescent 1,8-napthalimide-tagged polyacrylate PAA-F1 to serve as an “on line” indicator of polymeric scale inhibitor concentration has been tested in dynamic bench scale tests operating with EMEC facility, and in an industrial-scale in situ experiment run at a “Rosinka 10/20” cooling tower that provides the circulating water cooling of heat exchangers at rectification columns of ECOS-1 Co. site in Staraya Kupavna city, Russia. It has been demonstrated that the static beaker tests and the dynamic bench- and industrial-scale experiments may reveal rather different results. The latter exhibited a much higher sensitivity to the background iron cation concentration. It has been found that PAA-F1 may lose up to 17% of fluorescence intensity, while the losses of indifferent tracer, tetrasodium salt of 1,3,6,8-pyrenetetrasulfonic acid (PTSA) can exceed 80%. The Benсh-scale dynamic experiments on the fluorescence intensity of a fluorescent-tagged scale inhibitor at elevated concentrations of the background cations are recommended as an inevitable step for a proper estimation of fluorescent tracer validity for in situ applications. An industrial-scale 30-day experiment has demonstrated a good agreement of the fluorescent data with the conventional methods of cooling water control, and the feasibility of 1,8-naphthalimide tagged polyacrylate PAA-F1 application for in situ polymer concentration monitoring “on line”.

Int. J. Corros. Scale Inhib., , 3, 418-426 PDF (951 K)
doi: 10.17675/2305-6894-2018-7-3-11

Evaluation of the effectiveness of migrating corrosion inhibitors and hydrophobizers for protection against corrosion of steel reinforcement in concrete using bimetallic batch sensor

Voronezh State University, Universitetskaya pl., 1, 394006 Voronezh, Russian Federation

Abstract: A method is proposed for quantitative evaluation of the effectiveness of the protective action of hydrophobizers and inhibitors in relation to the corrosion process of reinforcement in reinforced concrete. Surface treatment of reinforced concrete structures with hydrophobizers leads to a significant increase in the specific electrical resistance of the protective layer of concrete. This makes it difficult to use electrochemical methods to determine the rate of corrosion of reinforcement, in particular, the method of polarization resistance. In this work, as a sensor for determining the rate of corrosion under a layer of concrete, it is proposed to use a bimetallic batch sensor – a package of galvanic cells (copper/low-carbon steel) capable of generating an electric current upon contact with the electrolyte. In this case, the copper plates of the sensor correspond to passive, steel – active sections on the surface of the steel reinforcement, and the magnitude of the current between the artificial cathode and anode can be considered as a measure of the corrosion rate of the reinforcement. The distance between the sensor plates is comparable to the distance between individual pits. Therefore, using the above described method, the corrosion process is modeled on the “active” sections of steel reinforcement, areas of microcell–pit/passive steel surfaces. The effectiveness of this method is demonstrated by the example of a commercial hydrophobizer based on alkoxysilanes, which also possesses inhibitory properties. Surface treatment of concrete samples contaminated with chlorides (1.00 and 3.25 mass% relative to the dry cement mass), a hydrophobizer, leads to a sharp decrease (up to 90%) of the galvanic current at the sensor. The protective effect persists for twenty cycles of wetting / drying (10 months) and when the water in the humidification cycle is replaced with a 3% solution of sodium chloride (six cycles of wetting / drying). When processing a concrete sample with a hydrophobizer, a sharp increase in the specific electrical resistance of concrete (up to 20 times on samples contaminated with chlorides) is observed and the potential for free corrosion of steel plates shifts to positive values. At the same time, the values of the potential of free corrosion and concrete resistivity of concrete, for the passive and active states determined by the sensor, meet the criteria given in RILEMTC 154-EMC. It is shown in the model calculations that an increase in the specific electrical resistance of the protective layer of concrete up to 10–20 times using a hydrophobizer can not explain the significant reduction in the corrosion rate (galvanic current at the sensor). It is suggested that a consistent change in corrosion rate and resistivity of the protective layer of concrete is due to a similar dependence of these values on the degree of filling of pores in the concrete with water.

Int. J. Corros. Scale Inhib., , 3, 427-442 PDF (633 K)
doi: 10.17675/2305-6894-2018-7-3-12

Macrocyclic compounds as green corrosion inhibitors for aluminium: electrochemical, surface and quantum chemical studies

  • , , , , , and
1 Center of Research Excellence in Corrosion, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia
2 Department of Chemistry, PSGR Krishnammal College for Women, Coimbatore 641004, Tamil Nadu, India
3 Department of Chemistry, Indian Institute of Technology (Banaras HinduUniversity), Varanasi 221005, India

Abstract: In the present work, two macrocyclic compounds namely 5,6,11,12-tetramethyl-1,2,4,7,8,10-hexaazacyclododeca-4,6,10,12-tetraene-3,9-dithione (TMCD) and 5,6,11,12-tetraphenyl-1,2,4,7,8,10-hexaazacyclododeca-4,6,10,12-tetraene-3,9-dithione (TMPD) have been synthesized and for the first time reported as inhibitors against the corrosion of aluminium in 1 M hydrochloric acid. The synthesized compounds were characterized using 1H NMR and 13C NMR. The corrosion inhibition behaviour of TMCD and TMPD was studied using gravimetric measurements, electrochemical impedance spectroscopy and potentiodynamic polarization studies. The surface analysis was carried out using AFM and SEM. Theoretical studies on the adsorption behaviour of inhibitor were carried out using the Density Functional Theory method. A detailed study of the effect of temperature and the influence of immersion time is presented using weight loss technique. Potentiodynamic polarization study proves that the corrosion inhibition efficiencies of TMCD and TMPD at 400 mg L–1 concentration are 97.30% and 89.71% respectively. Both the inhibitors behaved as mixed type but exhibit cathodic predominance. The results of EIS-Nyquist plots show inductive behavior at low frequency characteristic of the electrochemical behaviour of aluminium. The increase in polarization resistance with concentration suggests the adsorption and corrosion inhibition behaviour for both TMCD and TMPD. The AFM studies reveal a considerable decrease in surface roughness in the presence of inhibitors compared to blank sample and the SEM images show a highly smooth surface of the metal sample in the presence of inhibitors. The Fukui functions, global softness and Mulliken charges reveal that the sites for electrophilic attack are the hetero atoms. The frontier molecular orbital energies, the molecular orbital energy gap and the other quantum chemical parameters corroborated the experimental observations and suggested a better performance of TMCD compared to TMPD molecule.

Int. J. Corros. Scale Inhib., , 3, 443-459 PDF (1 695 K)
doi: 10.17675/2305-6894-2018-7-3-13

Prev. issue<- -> Next issue