2-mercaptobenzothiazole Research Articles

Patch Testing of Mercaptobenzothiazole and Mercapto Mix: The North American Contact Dermatitis Group Experience, 1994-2016.

Mercapto compounds are a category of rubber accelerators that may cause allergic contact dermatitis. This study characterizes patch test reactions to mercaptobenzothiazole (MBT) and mercapto mix (MM) in a large North American population. The 1994-2016 North American Contact Dermatitis Group screening series data were analyzed. Patients with allergic reactions to either MBT or MM (mercapto+) were included. The following characteristics were analyzed: strength of reaction, clinical and occupational relevance, coreactivity with other rubber accelerators, and sources of exposure. A total of 49,795 patients were tested to mercapto compounds from 1994 to 2016; 633 (1.3%) had positive reactions to MBT and/or MM. The frequency to both MBT and MM significantly decreased over time (P < 0.0001). Mercapto+ patients were significantly more likely to be male, have occupationally related skin disease, and report involvement of the hands and/or feet (P < 0.0001). They were significantly less likely to have face, scalp/ears/neck, or trunk involvement (P ≤ 0.0001). There was significant coreactivity with carba mix (23.4%) and thiuram mix (32.5%). Mercaptobenzothiazole and MM reactions were frequently clinically (81.7% and 83.5%, respectively) and occupationally relevant (29.8% and 33.4%, respectively). Gloves were the most common source (31.3% and 30.9%, respectively). Patch test positivity to mercapto compounds significantly decreased from 1994 to 2016 but remains clinically and occupationally relevant.

Thermal and mechanical behavior of SBR/devulcanized waste tire rubber blends using mechano–chemical and microwave methods

Abstract The engagement of waste tires rubber as source of raw materials for different applications can be a partial solution to the great environmental problems caused by these products. In this study, waste tire rubber was devulcanized using both mechano–chemical and microwave methods. This process was achieved using different concentrations of 2-mercapto benzothiazole disulfide (MBTS) and tetramethylthiuram disulfide (TMTD) as a devulcanizing agent and different microwave devulcanizing times. The optimum content of both MBTS, TMTD and suitable microwave treatment time to make continuous film were noted. The devulcanized waste rubber was then added, at different concentrations, to virgin styrene–butadiene rubber (SBR). The thermal properties and dynamic mechanical behaviors were investigated for all blends. The thermal analysis proved that natural and styrene butadiene rubber are the main two constituents of the waste tire rubber utilized in this study. The mechanical behavior of the SBR blends remarkably improved by using 20 phr waste rubber (WR) devulcanized by 2 phr MBTS and by exposure for 2.2 min to microwaves. Storage modulus, tearing strength and tension set behaviors notably improved for all SBR/WR blends by irradiating with gamma ionizing radiation with a dose of 100 kGy and further improvement could be attained by increasing the dose up to 200 kGy.

2-Mercapto Benzothiazole Derivatives: As Potential Leads for the Diabetic Management.

Results of our previous studies on antiglycation activity, and the noncytotoxicity of 2-mercapto benzothiazoles, encouraged us to further widen our investigation towards the identification of leads against diabetes mellitus. 33 derivatives of 2-mercapto benzothiazoles 1-33 were evaluated for in vitro α- glucosidase inhibitory activity. Mode of inhibition was deduced by kinetic studies. To predict the interactions of 2-mercapto benzothiazole derivatives 1-33 with the binding pocket of α-glucosidase enzyme, molecular docking studies were performed on the selected inhibitors. Compounds 2-4, 6-7, 9-26, 28 and 30 showed many folds potent α-glucosidase inhibitory activity in the range of IC50 = 31.21-208.63 μM, as compared to the standard drug acarbose (IC50 = 875.75 ± 2.08 μM). It was important to note that except derivative 28, all other derivatives were also found previously to have antiglycating potential in the range of IC50 = 187.12-707.21 μM. A number of compounds were identified as dual nature as antiglycating agent and α- glucosidase inhibitors. These compounds may serve as potential lead candidates for the management of diabetes mellitus.

Patch test results of 276 cases with footwear dermatitis - A retrospective study from a tertiary care centre in South India

Background:Allergic contact dermatitis (ACD) is a major cause for foot wear dermatitis. Patch testing is the standard investigation for diagnosis of ACD. Identification of the causative allergen and avoidance of the same is the most important for patient management.Aims:This study was conducted to find the common allergens in footwear, causing ACD, by retrospective analysis of the data of patients who had undergone patch testing with footwear series (FWS), approved by the Contact and Occupational Dermatoses Forum of India.Materials and Methods:A total of 276 cases with footwear dermatitis who underwent patch test with FWS using Finn chamber method were studied. Statistical analysis was done using statistical package for social sciences (SPSS) version 24. Data was described using frequency and percentages. P value of less than 0.05 was considered significant.Results:In this study 101 (36.5%) patients had positive patch test to at least one allergen. Among this, 43 (15.6%) were positive for single allergen only and 58 (21.01%) patients had positive patch test reactions to multiple allergens. The most common allergens with positive patch test were black rubber mix, mercapto benzo thiazole, and thiuram mix. Patients with either a positive or negative patch test had no statistically significant difference in the history of atopy. The limitations of this study include the lack of patch testing with the patient's own footwears and lack of follow-up after informing patients regarding allergen avoidance.Conclusions:Patch test must be done for all foot eczema cases for early identification of the causative allergen and also to provide suitable alternatives.

Clinico-demographic profile of patients with foot dermatitis: A cross-sectional study with special reference to patch test results

Background:Foot dermatitis is a common debilitating dermatological disorder where the eczematous process predominantly involves the feet.Aims and Objectives:To analyze the clinico-demographic profile, type, clinical pattern, and evaluate the role of patch testing to determine the causative factors of foot dermatitis.Materials and Methods:Fifty-eight new patients clinically diagnosed with foot dermatitis were subjected to detailed history taking and physical examination. The patients were subjected to patch testing using the Indian standard battery and Indian footwear series (Contact and Occupational Dermatoses Forum of India [CODFI]).Results:Among the 58 patients (mean age 31.48 ± 16.4 years, M:F 1:1.2), the majority (39.7%) presented with allergic contact dermatitis (ACD) followed by irritant contact dermatitis (ICD) (19%), while atopic dermatitis was the least (3.45%). However, 48% of our patients reported a history of atopy. About 43.5% of ACD patients showed a positive patch test reactions to at least one allergen of Indian standard battery and footwear series. Mercaptobenzothiazole (MBT) was the commonest allergen (50%), followed by potassium dichromate (40%), thiuram mix (20%) while paraphenylenediamine was the least common (10%). Dorsum of the foot was affected most commonly (55.17%), followed by toe (46.55%) and sole (41.38%). Scaling was observed in almost 80% of patients followed by crusting. Housewives were affected most commonly followed by students and cement workers.Conclusion:Rubber and rubber chemicals were found to be the commonest allergen inciting foot dermatitis. Atopy might be a predisposing factor in these patients. Thus, patch testing is recommended to determine the cause of foot dermatitis and provide suitable treatment.

Environmentally friendly Zn–Al layered double hydroxide (LDH)-based sol–gel corrosion protection coatings on AA 2024-T3

Zn–Al layered double hydroxide (LDH) intercalated with various corrosion inhibitors namely vanadate (E1), 2-mercapto benzothiazole (E3), molybdate (E7), phytic acid (E8) and 8-hydroxyquinoline (E9) was dispersed in a hybrid sol–gel silica matrix sol. Bilayer coatings with configurations E3|E1, E7|E1, E8|E1 and E9|E1 were generated on aluminum alloy AA 2024-T3 substrates using the inhibitor intercalated LDH modified sols by dip coating technique followed by UV curing and thermal curing at 80°C for 1 h in air. Corrosion resistance of coatings deposited from matrix sol with and without inhibitor intercalated LDH was studied by electrochemical impedance spectroscopy, potentiodynamic polarization after exposure to 3.5% NaCl and salt spray tests, results of which were compared with those of uncoated and chromated substrates. A non-chromated primer was applied on the sol–gel coated substrates. Adhesion of the coatings to the substrate and to the primer was evaluated by peel-off tape test and found to be rank 5. The sol–gel coated substrates did not exhibit corrosion during salt spray tests. Electrochemical tests showed that all the sol–gel coated substrates exhibited superior corrosion resistance when compared to bare and chromated substrates. More specifically, coatings generated using the corrosion inhibitors phytic acid and 8-hydroxy quinoline intercalated Zn–Al LDH were seen to render maximum corrosion protection, exhibiting two orders of magnitude lower corrosion currents than bare substrates and one order lower corrosion current than chromated substrate, after 120-h exposure to 3.5% NaCl solution.

Functionalized Halloysite Nanotubes⁻Silica Hybrid for Enhanced Curing and Mechanical Properties of Elastomers.

Vulcanization and reinforcement are critical factors in governing the ultimate practical applications of elastomer composites. Here we achieved a simultaneous improvement of curing and mechanical properties of elastomer composites by the incorporation of a functionalized halloysite nanotubes–silica hybrid (HS-s-M). Typically, HS-s-M was synthesized by 2-mercapto benzothiazole (M) immobilized on the surface of halloysite nanotubes–silica hybrid (HS). It was found that the HS-s-M uniformly dispersed in the styrene-butadiene rubber (SBR) matrix, offering more opportunity for M molecules to communicate with rubber. In addition, the physical loss of accelerator M from migration and volatilization was efficiently suspended. Therefore, SBR/HS-s-M composites showed a lower curing activation energy and a higher crosslinking density than SBR/HS composites. Moreover, a stronger interfacial interaction between HS-s-M and SBR was formed by the cross-linking reaction, giving a positive contribution to the eventual mechanical properties. The possible vulcanization and reinforcement mechanisms of SBR/HS-s-M composites were also analyzed in detail.

Effect of Ingredient Loading and Temperature on Tensile Properties of Surfactant-Loaded Natural Rubber Vulcanizates

Tensile properties are among the measures that give rubber products value. In this study, the effect of ingredient loading and temperature on the tensile properties of surfactant-loaded natural rubber vulcanizates (NRV) are investigated. Rubber dogbone samples are compounded using an L12 orthogonal array of Taguchi design of experiment, where ingredients are treated as factors varied at low and high loadings. Rubber specimens for each formulation are thermally aged for 20 days in ovens with temperatures of 40, 50, and 60 °C. Results show that zinc oxide (ZnO), paraffin wax, sulfur, mercaptobenzothiazole (MBT), and diphenylguanidine (DPG) significantly have the highest effect on increasing the elastic modulus while decreasing the tensile strength, tensile strain, and tensile set. Used oil has the highest effect on decreasing the elastic modulus but has the highest effect on increasing tensile strength, tensile strain, and tensile set. High loading of cocamide diethanolamide (coca DEA) significantly increases tensile strength at 60 °C. High loading of glycerol monostearate (GMS) significantly decreases tensile strength and strain at 40 °C. Highest elastic modulus, tensile strength, strain, and set are achieved when NRV are thermally aged at 50 °C.

Electrochemistry of corrosion mitigation of brasses by azoles in basic medium

The article describes the corrosion inhibition effects of four metal cations (Al, Sn, Pb, Mn) as dopants and five azoles as outer protective layers on pure copper and four brass alloys in borate buffer at pH 10.4. The electrochemical behavior of the four doped brasses, i.e., CuZnAl, CuZnSn, CuZnPb and CuZnMn was investigated using cyclic voltammetry (CV), potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy. The corrosion rate (CR) of all the brasses was found slower than that of pure Cu (0.132 mm year−1) due to the presence of dopant ions, i.e., CuZnMn had the highest CR, 0.019 mm year−1 and CuZnAl had the lowest 0.009 mm year−1. Five azoles, namely benzotriazole, mercaptobenzothiazole (MBT), benzimidazole, mercaptobenzimidazole and thiadiazole, were successfully employed as efficient corrosion retarders for the brasses. Their concentration-dependent corrosion inhibition was attributed to the spontaneous chemisorption on alloy surface following Langmuir isotherm pattern. Among all the inhibitors, MBT showed maximum corrosion inhibition efficiency between 91 and 96% for different brasses. The impedance modulus markedly increased with inhibitor concentration, revealing a protective effect of these corrosion inhibitors and thus complementing the CV and PDP results.

The synthesis of a new ionic liquid and its use as a multifunctional additive in different rubber composites

A novel functional ionic liquid (ILM) was synthesized using the ion exchange reaction of mercaptobenzothiazole (MBT) and 1-allyl-3-methylimidazolium. ILM was then added into carbon black/rubber, silica/rubber and microcrystalline cellulose (MCC)/rubber compounds, respectively, and its effects on the processing, physico-mechanical, and dynamic properties of the vulcanizates were investigated. For carbon black/rubber and silica/rubber compounds, ILM worked very well as a curing accelerator and surface modifier of carbon black and silica. For MCC/rubber compounds, the improvement was slight for the curing rate but obvious for the tensile properties. And it is noteworthy that the sizes of the MCC were decreased in situ from 20–90 μm to less than 5 μm during the processing of the rubber compounds, and the interfacial bonds between MCC and the rubber matrix were also improved. These results indicate that ILM is a multifunctional additive that can be used in different rubber composites.

Chitosan-based coatings for corrosion protection of copper-based alloys: A promising more sustainable approach for cultural heritage applications

The attractive physicochemical properties of chitosan make its derived materials promising candidates for the reliable and sustainable corrosion protection of metallic substrates. In this work, chitosan-based coatings embedding different corrosion inhibitors, i.e. benzotriazole (BTA) and mercaptobenzothiazole (MBT), were investigated for the protection of copper-based alloys, with the aim to extend their application to the preservation of works of art exposed to indoor atmosphere. The composition of the formulations was optimized paying particular attention to their potential application in the field of cultural heritage. To assess the efficacy of the coatings, tailored accelerated corrosion tests were carried out on bare and coated bronze substrates. Coated and uncoated alloy disks were characterized before and after corrosion treatments by optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. Moreover, an image analysis protocol was defined to evaluate the extent of surface modifications after degradation treatments. The obtained results revealed that the chitosan-based coatings containing BTA and MBT fulfil the aesthetic criteria required in the field of cultural heritage and are able to inhibit the corrosion of bronze alloys. It is worth noting that a synergic effect between the chemical protection provided by the inhibitors and the physical one provided by the polymer matrix was observed. Our findings demonstrate that the developed systems are suitable for a reliable and more sustainable protection of indoor bronze artefacts, thus representing a promising alternative to commercial products and particularly taking advantage from the use of non-harmful solvents for their application and removal.

Self-healing capability of inhibitor-encapsulating polyvinyl alcohol/polyvinylidene fluoride coaxial nanofibers loaded in epoxy resin coatings

The self–healing capability of epoxy coatings modified with coaxial core–shell nanofibers loaded with the corrosion inhibitor 2–mercaptobenzothiazole (MBT) was investigated using electrochemical techniques. The polyvinyl alcohol/polyvinylidene fluoride core–shell nanofibers were prepared by coaxial electrospinning. Electrochemical impedance results showed that the MBT–loaded coaxial nanofibers improved the barrier properties and decreased the corrosion activity of the coatings. Results of the Scanning Kelvin Probe technique revealed that the MBT–loaded coaxial nanofibers healed corrosion over artificial defects exposed to NaCl electrolytes. These results indicate that adding MBT–loaded coaxial nanofibers to epoxy coatings is a promising strategy toward the development of self–healing epoxy coatings.

Focused library design and synthesis of 2-mercapto benzothiazole linked 1,2,4-oxadiazoles as COX-2/5-LOX inhibitors

Mercapto benzothiazole linked 1,2,4-oxadiazole derivatives were designed (4a-u) as new anti-inflammatory agents using bioisosteric approach and docking studies. The docking results clearly indicated that the compounds 4a-u shown good docking interaction towards COX-2 enzyme. In silico drug-like properties were also calculated for compounds (4a-u) and exhibited significant H-bond acceptor ratio. All compounds were synthesized and biologically evaluated using in vitro COX-1, COX-2 and 5-LOX assays. Compound 4k and 4q (IC50 = 6.8 μM and IC50 = 5.0 μM) found to be potent, selective COX-2 inhibitors and display better anti-inflammatory activity than standard Ibuprofen. Compound 4l and 4e found to be potent inhibitors against 5-LOX (IC50 = 5.1 μM and IC50 = 5.5 μM). The in vivo anti-inflammatory activity studies shown that the compounds 4q and 4k effectively reducing the paw edema volume at 3h and 5h than standard drug Ibuprofen. The DPPH radical scavenging activity provided anti-oxidant activity of compound 4e (IC50 = 25.6 μM) than reference standard Ascorbic acid.

The synthesis and application of the SiO2@Fe3O4@MBT nanocomposite as a new magnetic sorbent for the adsorption of arsenate from aqueous solutions: Modeling, optimization, and adsorption studies

This study was conducted for the purpose of showing that the mercaptobenzothiazole (MBT)-functionalized SiO2@Fe3O4 nanocomposite can be applied as a new adsorbent for the adsorption of As (V) ions from aqueous solutions. SiO2@Fe3O4@MBT synthesized via a two-stage process was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), the transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET). The SEM showed good adsorbing capacity for SiO2@ Fe3O4@ MBT due to the average core size 40nm with a vast surface. The appearance of bands attributed to the CH stretch of methylenes of the alkyl chain in FTIR analysis showed SiO2@Fe3O4 was successfully modified by MBT. The XRD spectrum clearly demonstrates the occurrence of two phases of iron oxide/hydroxide and silica oxide, and also the spinal structure of SiO2@ Fe3O4@ MBT reveals the presence of SiO2, by revealing the specific peaks at 2θ=26.62, 39.44, 42.41, 54.83.The TEM micrograph of SiO2@ Fe3O4@ MBT showed the Fe3O4 nanoparticle anchored on SiO2 and formed a large amount of Fe3O4 with different size. Surface area of SiO2@ Fe3O4@ MBT was investigated and determined 58.35m2/g. Response surface methodology (RSM) was employed to model the effects of the operating parameters, such as pH (2–8), adsorbent dosage (10–100mgL−1), initial As (V) concentration (1–10mgL−1), and contact time (2–180min) using the R software. Based on the results obtained from the analysis of variance (ANOVA), the reduced full second-order model demonstrated satisfactory adjustment with the experimental data. The Solver “Add-ins” were applied using the effective parameters to optimize important operating variables. The optimum operating points were established at the initial As (V) concentration of 10mg L−1, the adsorbent dosage of 82.7mg L−1, the time of 169.1min, and the pH of 5.07, corresponding to the maximum predicted As (V) removal percentage of 93.89%. Based on the reported results, the experimental isotherm data best fit the Freundlich model rather than the other isotherms. The maximum adsorption capacities calculated from the Langmuir equation were 10.38, 11.35, and 17.5mg g−1 for 291K, 301K and 311K. The followed kinetic model was the pseudo-first order kinetic model in nature and intraparticle diffusion was the dominant mechanism.

Mercaptobenzoheterocyclic compounds functionalized silver nanoparticle, an ultrasensitive colorimetric probe for Hg(II) detection in water with picomolar precision: A correlation between sensitivity and binding affinity

Toxic heavy metal ions, specially Hg(II) pose lethal threat to the environment and human beings. To this end, there is a strong need to establish a simple, inexpensive method for the detection of Hg(II) ions with high selectivity and sensitivity in aqueous medium. Herein, we report an ultra-sensitive colorimetric detection of Hg(II) ions following a simple protocol by synthesizing silver nanoparticles functionalized with mercaptobenzoheterocyclic compounds (viz. mercaptobenzooxazole (MBO), mercaptobenzoimidazole (MBI) and mercaptobenzothiazole (MBT). These nanoparticles are found to show a limit of detection (LOD) of 1.8ppt (9.2pM), 9.2ppt (46pM) and 18.4ppt (92pM) for MBO, MBI and MBT respectively). In addition, the binding affinity trend of the mercaptobenzoheterocyclic ligands seems to be in tune with the observed sensitivity trait of Hg2+ sensing.

CURE CHARACTERISTICS OF DEVULCANIZED RUBBER:THE ISSUE OF LOW SCORCH

ABSTRACT We investigate the reasons behind the observed low scorch during the revulcanization of devulcanized rubber. Mechanically devulcanized carbon black filled natural rubber vulcanizates originally cured by conventional vulcanization (CV), semiefficient vulcanization (semi EV), efficient vulcanization (EV), and peroxide systems as well as buffing dust obtained from pre-cured tread with known formulation were used. Revulcanization of these devulcanized samples using sulfur/sulfonamide system led to the following observations; irrespective of the type of sulfur cure system used for the initial vulcanization of the rubber, (i) the devulcanized samples cured without pre-vulcanization induction time and (ii) devulcanized samples prepared from peroxide vulcanized rubber cured with scorch safety. Based on the earlier reports that solvent extraction of devulcanized rubber did not improve the scorch time during revulcanization, the role of zinc bound non-extractable moieties was investigated using devulcanized rubber prepared from activator-free vulcanizates, which disproved the role of such moieties. This confirmed that the scorch reducing moieties should be attached to the rubber main chain, which can be unreacted crosslink precursors and cyclic sulfides left after the initial accelerated sulfur vulcanization of the original sample. The ability of pre-vulcanization inhibitor to induce scorch safety when devulcanized rubber is revulcanized as such, without adding any virgin rubber, proved that mercaptobenzothiazole (MBT) generated from crosslink precursors is the cause of low scorch. Acetone extracted devulcanized rubber samples prepared from tetramethyl thiuramdisulfide (TMTD) cured natural rubber, which does not follow the MBT pathway when revulcanized, cured with scorch safety, which further proved the role of MBT. Based on the previous reports and our results, it is obvious that powdering of rubber vulcanizate and devulcanization processes have no role on the low process safety of these materials, but it is inherent to the initial accelerated sulfur vulcanization chemistry undergone by these materials.

Nickel(II) Determination by Anodic Stripping Voltammetry

This study was aims to develop the new electrochemical method for the determination of Ni (II) using glassy carbon electrode. Three supporting electrolytes were used to find the peak of Ni (II), they were sodium chloride, acetic buffer solution, and ammonium choride. The peak of nickel was found in the condition of 0.1 M ammonium chloride solution (pH 4.5) as supporting electrolyte, deposition potential of -1.0 V (vs. Ag/AgCl) and a deposition time of 180 s, 10 s equilibration time, and the potential step, amplitude, and frequency were 25 mV, 5 mV, and 25 Hz , respectively. The anodic peak of Nickel was found at around -0.325 V. Then, the GCE was modified with 2-MBT and Bi (III) to increase the current. Both of chemicals were done in both in-situ and ex-situ techniques. The presence of Bi (III) in the electrochemical system can increase the current. It needs further experiment to get the best response of Ni (II) determination by ASV methods.

Evaluation of the mercaptobenzothiazole degradation by combined adsorption process and Fenton reaction using iron mining residue

ABSTRACT The present study investigated the degradation of mercaptobenzothiazole (MBT), evaluating homogeneous and heterogeneous systems. An iron mineral residue from the desliming step of iron mining was used as a source in the Fenton-like reaction (advanced oxidation process). A granulometric analysis of the residue was performed and yielded fractions with high hematite (Fe2O3) and low quartz content in sieves from 74 to below 44 mm. In this particle size range, the hematite content from 58.9% to 67.4% and the Brunauer-Emmett-Teller area from 0.1345 to 1.3137 m2 g−1 were obtained. The zeta potential curves as a function of pH were obtained for the residue, the MBT solution and mixtures thereof. The adsorption of MBT in the residue and its degradation through the Fenton-like reaction were investigated. Adsorption tests and the Fenton-like reaction were carried out, where the MBT species and the residue are oppositely charged, yielding, respectively, 10% MBT adsorption on the surface of the residue and 100% MBT degradation by the Fenton-like reaction at pH 3, hydrogen peroxide concentration of 25 mg L−1, residue concentration of 3 g L−1, 200 rpm and 25°C, from a 100 mg L−1 MBT solution. MBT degradation was found to occur mainly by the heterogeneous Fenton-like process.

Aqueous Dispersions of Latex Compounding Ingredients by Wet Ball Milling: Effect of Ball Size and Milling Time on Dispersion Quality

Preparation of nanomaterials, their functionalization, evaluation and usage for potential applications are the main objectives in materials science research. Preparation of ultra-fine/nano-sized particle dispersions and their stabilization is a great challenge among researchers where the high surface area and energy impedes the effective usage of nanomaterials. This study presents the effect of ball milling on size and stability of aqueous dispersions of latex compounding ingredients such as china clay, zinc diethyldithiocarbamate, zinc 2-mercapto benzothiazole and butylated reaction product of p-cresol and dicyclopentadiene (wingstay L). The particle size and stability have been assessed through dynamic light scattering technique and sedimentation test. By using lower sized balls for milling, the particle size of latex compounding ingredients can be reduced to a great extent.

(Keynote) Local Electrochemical Impedance Spectroscopy: A Powerful Tool for Studying Corrosion Inhibition Mechanisms on 2024 Aluminum Alloy

Corrosion phenomena on aluminum alloy such as AA2024 are mainly linked to the local galvanic coupling between the intermetallic particles and the surrounding matrix [1]. To have a better understanding of the corrosion associated with copper-rich intermetallics, a simple system consisting of pure aluminum/pure copper (Al/Cu couple) has been previously considered [2]. From the beginning of immersion, increased cathodic activity related to oxygen reduction was observed at the Al/Cu interface. It was underlined that the local alkalinization of the electrolyte at the Al/Cu interface plays a key role in the degradation of the system. In a recent work devoted to the corrosion inhibition of the 2024 aluminum alloy, it was shown that mixing 8-hydroxyquinoline (8-HQ) and benzotriazole (BTA) led to a synergistic effect for the corrosion protection of the alloy [3]. This synergy was observed by conventional electrochemical measurements (current-voltage curves and global impedance spectroscopy). However, the electrode response corresponds to a surface-averaged measurement ascribable to the behavior of the whole electrode surface. Thus, local impedance measurements were performed on the model Al/Cu couple to analyze the role of the inhibitors on the galvanic coupling. It was shown that the galvanic coupling responsible for the corrosion process is strongly limited by mixing the two compounds which is not the case when the inhibitors are used separately. The synergistic effect was explained by the two different mechanisms by which BTA or 8-HQ inhibit corrosion: the action of BTA is mainly limited to the copper-rich intermetallic particles; 8-HQ acts on the aluminum matrix due to its chelating properties. In the present work, the same methodology was proposed to evaluate and to compare different compounds known for their effectiveness as corrosion inhibitors for the 2024 aluminum alloy [4-11]. The electrochemical measurements were carried out in a neutral NaCl solution, in presence of 8-hydroxyquinoline (8-HQ), benzotriazole (BTA), mercaptobenzothiazole (MBT) and a cerium salt. The compounds were used alone or as inhibitive mixtures and for various concentrations. Current-voltage curves and impedance measurements confirmed that the compounds are effective inhibitors for the aluminum alloy. Performing local electrochemical impedance measurements on the Al/Cu model allow to better understand the action of each compound on the galvanic coupling. The protective properties of the corrosion inhibitors were compared and discussed.