Coal Tar Epoxy Research Articles

Effect of coal tar pitch modification on the structure and char yield of pyrolysis epoxy resin carbons

Epoxy resin carbons are of high strength, high temperature resistance, and corrosion resistance, which are widely used as the precursor of carbon composite materials. However, the applications of epoxy resin carbons are greatly limited for the characteristic of non-graphitization and low char yield (22 wt%). In this paper, coal tar pitch was used to modify epoxy resin carbons via a simple heating mixing, pyrolysis and high temperature graphitization. The results show that the coal tar pitch content and heat treatment temperature can improve the ordered graphite carbon content. As the coal tar pitch content increase, the ordered graphite carbon content of modified epoxy resin carbon increase after 3000 °C graphitization for 0.5 h. Particularly, the graphitization degree of epoxy resin carbon and 40 wt% coal tar pitch modified epoxy resin carbon are 8.42 % and 44.21 %, respectively. The grain size (Lc = 13.84 nm) and grain stacking height (La = 7.79 nm) of 40 wt% coal tar pitch modified epoxy resin carbon are bigger than epoxy resin carbon (Lc = 3.44 nm, La = 3.45 nm). The ordered coal tar pitch graphite carbon and disordered epoxy resin amorphous carbon are evenly distributed in the modified epoxy resin carbon, indicating a good comparability of coal tar pitch and epoxy resin. Besides, the entangling carbon ribbon are observed in the epoxy resin carbon after graphitization at 3000 °C. With the coal tar pitch content increasing, the carbon element content and aromatic ring number of modified epoxy resin increased. As the coal tar pitch content increase, the char yield and thermal decomposition temperature of modified epoxy resin gradually increase. The char yield of 50 wt% coal tar pitch modified epoxy resin is 42 wt%, almost double that of epoxy resin (22 wt%). The char yield increased values of modified epoxy resin mainly inherited the high char yield of coal tar pitch (50 wt%) and a small portion of char yield increased value is from the chemical crosslinking weight gain. When the coal tar pitch content is 40 wt%, the chemical crosslinking weight gain reaches the maximum value of 15 wt%. Possible chemical crosslinking reaction can be epoxy group and hydroxyl group of epoxy resin and carboxyl group and phenolic hydroxyl group of coal tar pitch. This study provides some theory foundation for the future application of epoxy resin carbon composite materials.

A SUSTAINABLE APPROACH TO IMPROVEMENT OF CORROSION PROTECTION COATINGS FOR STEEL STRUCTURES

Corrosion is a primary factor compromising the safety and service life of steel structures. Corrosion protection coatings are generally employed for protection of the steel structures that are exposed to different aggressive environments. This research evaluated the use of biobased ion exchangers as a sustainable means of improving corrosion protection coatings.
 Two base polymer coatings (vinyl and coal-tar epoxy) were considered. The following types and dosages of biobased ion exchangers were evaluated in these coatings: (i) strong-base ion exchange cellulose in OH, PO4, SiO3, BO3, NO2, SO4 and NO3 forms at 1% by weight of resin; (ii) weak-acid starch citrate ion exchanger in H form at 1 wt.%; and (iii) strong-base ion exchange cellulose in OH form at 2 wt.%. In addition, a strong-base ion exchange resin in OH form was considered at 1 and 2 wt.% as control. Different coating formulations were evaluated based on the outcomes of salt-fog corrosion, moisture resistance, pull-off strength, and abrasion resistance tests. The introduction of certain biobased ion exchangers in protective coatings was found to be an effective means of achieving improved levels of corrosion resistance, adhesion capacity, moisture stability and abrasion resistance.

Development of coal tar-free coatings: Acetylated lignin as a bio-additive for anticorrosive and UV-blocking epoxy resins

Coal tar epoxy (CTE) coatings promote effective protection of steel structures under critical conditions of atmosphere and immersion. However, according to the international guideline, coal tar has been reported as a mutagenic and carcinogenic compound and has been prohibited for use in countries such as the USA and Japan. Aiming to replace the use of CTE coatings, this paper proposes the use of Kraft lignin, a bio-polyphenol considered safe and obtained as waste from the pulp and paper industry, to develop a coal tar free epoxy coating. In order to promote better compatibilization with bisphenol A diglycidyl ether (DGEBA), lignin was subjected to the acetylation process. The epoxy-lignin resin was obtained by incorporating acetylated lignin into DGEBA. Three types of epoxy-lignin resin were prepared, namely: DGEBA/7.5% lignin, DGEBA/15% lignin and DGEBA/30% lignin. The chemical structure of the resin was evaluated by Fourier transform infrared spectroscopy (FTIR). For the coating preparation, the resin was cured using isophorone diamine (IPDA). The resultant thermosetting were analyzed regarding their chemical, thermal, anticorrosive and UV-blocking properties using the DGEBA and CTE coatings as reference. The anticorrosive properties of the coatings were evaluated by electrochemical impedance spectroscopy (EIS). The adhesion of the coatings was evaluated by the pull-off method (ASTM D4541). A complete absorption of UV light in the UV-A and UV-B regions was observed in the coatings add with acetylated lignin, a property very valuable in order to prevent the UV damage and the durability reduction of epoxy coatings. EIS results showed that the epoxy-lignin coatings (with 7.5 and 15% lignin content) presented modulus of impedance values comparable to the commercial coating and superior to the CTE coating, indicating the potential use of this coating as a corrosion protector.

Surface Modification of a Graphite Fiber Fabric Anode for Enhanced Bioelectrochemical Methane Production

The graphite fiber fabric (GFF), modified using different methods, was studied as an anode for enhanced bioelectrochemical methane production. The electrical conductivity of the GFF was significantly improved by loading the multiwall carbon nanotube (MWCNT) on the GFF surface via electrophoretic deposition (EPD) or the sonication method. The surface-modified GFF anodes were obtained by further processing to form a scaffold layer of exfoliated graphite (EG) and the MWCNT mixture using coal tar pitch or epoxy as the binder. In the batch bioelectrochemical reactor, the lag time for the GFF control anode was about 15.5 days in the methane production during the enrichment of electrochemically active bacteria (EAB). Interestingly, the lag time for the modified anode was increased more by the EPD treatment (20.8–23.3 days) than by the sonication (17.1–18.4 days) and was increased more by the epoxy binder (EB) (18.4–23.3 days) than by the coal tar pitch binder (CB) (17.1–20.8 days). However, the accumulated metha...

Evaluation of microbial corrosion of epoxy coating by using sulphate reducing bacteria

Abstract The deterioration of coatings by microbiological attack takes place directly or indirectly as a result of metabolic activity of microorganisms. The most severe bacterial corrosion occurs due to presence of sulphate reducing bacteria (SRB), as these produce hydrogen sulphide, leading to formation of metal sulphides and sulphates. Such type of microbiological corrosion can be controlled by incorporating suitable biocide in the coating. The objective of this study was to simulate such microbiological corrosion phenomena in the laboratory and observe its effect on the coating performance. In the present work, experiments were conducted to assess the antibacterial property of epoxy based anticorrosive coatings, with and without of biocide, by exposing them to SRB culture under anaerobic condition. Coal tar epoxy (CTE)-polyamide coating system which is known for superior antibacterial properties was selected as benchmark. The SRB effectiveness was evaluated by the formation of zone of inhibition in nutrient agar and visual observation. The surface morphology of coatings before and after exposure was analysed by scanning electron microscopy (SEM). The anticorrosive property of these coatings under SRB exposure was also monitored by measuring impedance of the coating by electrochemical impedance spectroscopy (EIS). The loss in adhesion after exposure was also measured for all the coatings.

Spatial Evaluation of Preservability of Mild Steel by Coal Tar Epoxy Coatings Via Spectroscopic and Microscopic Techniques

Generally film coatings are formulated by accounting average weather conditions, corrosivity level and any metal substrate, while accelerated (salt spray) test usually considered adequate to predict performance of a coating system. This established a need to evaluate compatibility of a coating system to a particular operational conditions for preservation of underlaying substrate metal. In this communication, epoxy-polyamide primer and coal tar epoxy topcoat system were tested for preservation of mild steel under various natural exposures including marine, industrial and urban test sites of Karachi city, while accelerated test was also conducted for comparison. Condition of coating was assessed by visual morphological inspection, gloss measurements, scanning electron microscopy (SEM), energy-dispersive X-ray analysis and by oxygen/carbon ratios. Resulted data were statistically analyzed through principal component analysis and explained a variance of 99.82 % when two components were considered. Severe blistering, acute loss of gloss and high degradation in the surface characteristics of coal tar epoxy coating systems were noticed after natural exposure testing at marine and industrial sites as compared to accelerated (salt spray) testing. However, comparison of performance of coal tar epoxy coating systems applied on mild steel with our previous study on electrogalvanized mild steel has shown faintly better preservability of mild steel samples by coal tar epoxy coating systems. This was also proved by relatively lower oxygen/carbon ratios for the coating systems applied on mild steel which correspond to lower coating degradation products.

Quantification of protective properties of the coating/corrosion product/steel interface by integration of transmission line model with EIS results

An experimental set up was designed to characterize and quantify the protective properties of coated steel samples over time. A porous layer of corrosion products (FexOy) was formed on the metal surface prior to coating application to simulate the coating disbondment condition. The detailed sample system configuration is as follows: coal tar epoxy coating/corrosion product/steel substrate. A continu- ous damage evolution mechanism was proposed which contains the following three stages: (I) mass transport within the coating and the corrosion porous layer, (II) mass transport and charge transfer mechanism mixture due to the formation of active sites beneath the coating layer, and (III) charge transfer dominant mechanism due to adsorption and electrochemical reaction. This damage evolution concept was supported by the experimental results in this work. Based on the electrochemical impedance spectroscopy (EIS) tech- nique, we observed that the sample system underwent stage I when initially immersed in an electrolyte solution. By evaluating the induced disbondment conditions, transitions from stage I to stages II and III were observed during the experimental period. After 55 days of exposure, stage III was identified in the EIS spectra. A transmission line model and EIS analysis was applied to each experimental condition. The simulated impedance magnitude has a good agreement with the experimental results.

Pipeline Anticorrosion Materials and Development Trend

Introduced the current situation at home and abroad pipeline anticorrosion technology, commonly used in the melting epoxy powder, adhesive tape, anticorrosion, multilayer structure coal tar epoxy, polyurethane extruded polyethylene anticorrosion technology. High performance synthetic resin, filler, pigment, anticorrosion material will have greater development, along with the application of pipeline anticorrosion technology in construction, chemical, oil and other industries, the pipeline anticorrosion technology will have larger development space.

Synergistic Corrosion Mitigation Appraisal of Coal Tar Epoxy Duplex Coating System by Spectroscopic and Microscopic Techniques

Epoxy-polyamide primer and coal tar epoxy topcoat system were tested to evaluate preservation of electrogalvanized mild steel (EGMS) under various naturally stimulated exposures including marine, industrial and urban test sites of Karachi city, while salt spray test was also conducted for comparison. Condition of coating was assessed by visual morphological inspection, gloss measurements, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis and oxygen–carbon ratio techniques. Results indicated that the natural exposure testing (particularly at marine and industrial test sites) caused extremely high degradation of coal tar epoxy duplex coating systems as compared to accelerated testing. SEM has also revealed high degradation in the surface characteristics of the coating applied on EGMS after natural exposure testing. This is most likely due to the presence of several corrosive components of environment, emerging from the mist of salt spray in the atmosphere and pollution due to industry and automobiles. In addition to this, it was also found that the major modes of degradation were completely different in accelerated and natural exposure testing. Comparison of the results of coal tar epoxy coating systems applied on EGMS with our previous study on mild steel revealed high photodegradation of the coating systems applied on EGMS in natural exposure testing, i.e., oxygen/carbon ratios as determined by (EDX) analysis were higher for the coating systems applied on EGMS.

Mechanical and anticorrosive properties of non toxic coal-tar epoxy alternative coating

Coal tar epoxy (CTE) coating system has been widely used for protection of steel structures under atmospheric, buried and immersion conditions because of their low water vapour permeability, high electrolyte resistance and good antibacterial properties. However, coal tar has been classified as carcinogen, mutagen and toxic for reproduction (CMR) as per International guideline (REACH, IARC and GS 11). It is now banned in the developed nations like US, Europe, Japan, etc. As the use of coal tar is being restricted, there is an urgent need to formulate a coal tar free epoxy product for corrosion protection of structures. In the present study, alternative approaches have been proposed to replace coal tar such as bitumen (BIT), hydrocarbon resin (HR), flexibilizer (FL) and curing agents like polyamide (PAD) or polyamine (PAM). Four different coal tar free formulations were formulated separately by using these approaches. The standard CTE and coal tar free epoxy compositions were evaluated for mechanical properties such as elongation at break, tensile strength, adhesion strength and resistance to abrasion, impact and flexibility. The resistance to corrosion of optimized composition (epoxy-HR-FL-PAD-PAM) and coal tar epoxy coating was evaluated by exposing to different environments. The corrosion resistance property was also evaluated by cathodic disbondment and electrochemical impedance spectroscopy (EIS) technique. Results indicate that epoxy-hydrocarbon resin-flexibilizer composition cured with blend of polyamide and polyamine has comparable mechanical and corrosion protection properties to that of standard CTE.

Effect of curing methods on strength and durability of concrete under hot weather conditions

This paper reports the results of a research study conducted to evaluate the effect of curing methods on the mechanical properties of ordinary Portland cement (OPC) and Silica Fume Cement (SFC) concretes. Slab and beam specimens were prepared and cured by covering them with wet burlap or applying a curing compound under field conditions. Four types of curing compounds, namely water-, acrylic-, and bitumen-based and coal tar epoxy, were applied on the concrete specimens. The curing compounds were applied immediately after casting or after an initial period of burlap curing. The effect of the selected curing regime on the properties of OPC and SFC concrete specimens was evaluated by measuring compressive strength, water-absorption and chloride permeability. The strength and durability characteristics of both OPC and SFC concrete specimens cured by applying the selected curing compounds were similar or better than that of concrete specimens cured by covering with wet burlap. Though no significant change in strength could be noted due to the curing methodology; however, its effect was noticeable on the durability. The best performance was shown by concrete specimens cured by applying the bitumen-based curing compound followed by those cured by applying coal tar epoxy, acrylic-based or water-based curing compound. The initial period of water curing, prior to the application of the curing compound, was also noted to be beneficial in increasing the durability of concrete.

Effect of curing methods on shrinkage and corrosion resistance of concrete

Abstract This paper reports the results of a study conducted to assess the effect of curing on shrinkage and corrosion resistance of OPC and silica fume cement concretes. The concrete specimens were cured by covering with wet burlap or applying one of the following curing compounds, water-, acrylic-, bitumen-based, or coal tar epoxy. The results indicated that the selected curing compounds were effective in decreasing the shrinkage strain and enhancing the corrosion resistance of both OPC and silica fume cement concretes. It was also noted that 3 days of wet burlap curing prior to the application of a curing compound was necessary for the OPC concrete while 7 days of wet burlap curing is required for the silica fume cement concrete.

Metallic Under-Layer Coating as Third Line of Protection of Underground Oil and Gas Pipelines from External Corrosion

This paper presents the concept of introducing a third line of defense in the form of a metallic under-layer coating—in addition to the traditional polymeric coating and applied cathodic protection (CP)—to protect the external surface of oil and gas pipelines. The three levels of protection would be the metallic under-layer coating, the polymeric top-layer coating, and the applied CP. This three-level system would be beneficial when the applied CP current is shielded from the pipeline by a dis-bonded polymeric coating, thermal insulator, or highly resistive soil. Two different combinations of metallic under-layer and polymeric top-layer coatings are presented to demonstrate this concept: 48%Zn and 52%Al under-layer with four different top-layer coatings: fusion-bonded epoxy (FBE), composite, urethane, and coal tar epoxy. Urethane top-layer coating with four different metallic under-layers: 48%Zn-52%Al, 85%Zn-15%Al, Al, and Zn. The criteria for the successful application of this concept also have been described.

A comparison between electrochemical noise and electrochemical impedance measurements performed on a coal tar epoxy coated steel in 3% NaCl

The protective performance of epoxy coatings on mild steel immersed in 3.5% NaCl solutions was evaluated by means of electrochemical noise analysis and electrochemical impedance spectroscopy (EIS). Current and voltage noise were recorded and the standard deviations of the potential, current and noise resistance were calculated. Additionally, the spectral noise resistance (RSN) was obtained from the harmonic analysis of the noise data. Finally, EIS measurements were carried out and the data fitted with an equivalent circuit from which the polarization resistance was obtained. Resistance parameters obtained by both techniques were found to be in good agreement. A set of parameters obtained from electrochemical noise measurement is proposed to be used for the assessment of the performance of protective coatings.

Laboratory Studies on Pipeline Coating Materials under Accelerated Weathering Condition

Laboratory test has been carried out to assess the rate of degradation of dielectric strength of different pipeline coating materials viz coal tar enamel, hot applied coal tar tape, cold applied polyolefin tape, coal tar epoxy, high build epoxy, polyurethane & 3LPE coating after accelerated weathering in QUV using 313 UVB lamp maintaining a cycle of 4 hour UV and 4 hrs. condensation and after 500 hours salt spray as per ASTM B117. This test is important since the corrosion control systems of most pipelines consist of the combination of coating and cathodic protections. It is desirable that the dielectric properties of the coating deteriorate at the minimum rate possible. Deteriorations of coating with time would lead to a constant requirement of additional cathodic protection current which would be both a technical & economic burden on the pipeline operator. This paper highlights to establish the suitability of proper coating material with respect to cathodic protection.

Ask Joe Powder: Suitability of powder coatings for military applications

Coal tar epoxy (CTE) coating system has been widely used for protection of steel structures under atmospheric, buried and immersion conditions because of their low water vapour permeability, high electrolyte resistance and good antibacterial properties. However, coal tar has been classified as carcinogen, mutagen and toxic for reproduction (CMR) as per International guideline (REACH, IARC and GS 11). It is now banned in the developed nations like US, Europe, Japan, etc. As the use of coal tar is being restricted, there is an urgent need to formulate a coal tar free epoxy product for corrosion protection of structures. In the present study, alternative approaches have been proposed to replace coal tar such as bitumen (BIT), hydrocarbon resin (HR), flexibilizer (FL) and curing agents like polyamide (PAD) or polyamine (PAM). Four different coal tar free formulations were formulated separately by using these approaches. The standard CTE and coal tar free epoxy compositions were evaluated for mechanical properties such as elongation at break, tensile strength, adhesion strength and resistance to abrasion, impact and flexibility. The resistance to corrosion of optimized composition (epoxy-HR-FL-PAD-PAM) and coal tar epoxy coating was evaluated by exposing to different environments. The corrosion resistance property was also evaluated by cathodic disbondment and electrochemical impedance spectroscopy (EIS) technique. Results indicate that epoxy-hydrocarbon resin-flexibilizer composition cured with blend of polyamide and polyamine has comparable mechanical and corrosion protection properties to that of standard CTE.

Corrosion Protection Mechanism of Polyaniline Blended Organic Coating on Steel

Epoxy–coal tar coatings are widely used to protect steel structures exposed to marine atmosphere due to their good barrier property. However, the presence of micropores and microcracks formed during the coating formation leads to failure of the coating due to permeation of corrosive ions. In recent years, it has been established that the coatings containing polyaniline (PANI) is able to protect pinholes and defects due to its passivating ability. Hence, a study has been made on the effect of polyaniline content (1 and 3%) in epoxy–coal tar coating on the corrosion protection of steel in 3% NaCl solution by electrochemical impedance spectroscopy (EIS) studies. Both phosphate- and chloride-doped polyanilines were prepared by a chemical oxidative polymerization method. From EIS studies, it has been found that the resistance value of the coatings containing 1 and 3% phosphate-doped polyaniline and 3% chloride-doped polyaniline pigmented coatings are even after exposure to NaCl solution, which are two orders high in comparison to that of conventional coal tar epoxy coatings. Besides, the conducting state of polyaniline has been found to be decreased after exposure to NaCl solution due to redox property of PANI. X-ray photoelectron spectroscopy studies have shown that polyaniline forms a complex layer with iron beneath the coating along with iron oxide.

Protective performance of epoxy resin modified with coal tar coating studied by electrochemical impedance spectroscopy

The effect of different amounts of titanium powder, used as additive, on the protective performance in aqueous 3.5 wt.% sodium chloride solution of coal tar epoxy resin cured with polyamine has been studied by electrochemical impedance spectroscopy (EIS). In this paper, the electrochemical impedance spectra and breakpoint frequency ( f b) of the coating as a function of titanium content and immersion time, and the electrical resistance of the coating by calculating permittivity of the coating were analyzed and discussed. It is shown that EIS performance of the coating can be explained by change of the permittivity of the coating with time, and the protective performance (the protective life) is determined by the breakpoint frequency of the coating in given system.

Investigation of marine environmental related deterioration of coal tar epoxy paint on tubular steel pilings

In the Arabian Gulf region, port and waterway authorities are becoming increasingly concerned about accelerated tidal and splash zone concentrated corrosion on marine tubular steel piles. The coating protection and maintenance of tubular steel pilings located in a marine environment can be difficult. The arid environment of Kuwait of the salt water and salt laden moisture and high temperature fluctuation with the marine growth on the marine structure creates a challenging maintenance problem. This premature failure investigation dealt with the delamination and peeling of coal tar epoxy coating system. The new pier project is around 2.5 km long with topside facilities supported by 2000 tubular steel pilings in two types 914 mm and 1016 mm in diameters. Prior to installation, the piles at vendor's premises in another country received a protective coal tar epoxy coating with a minimum dry film thickness of 450 microns. However, almost all of the coated steel pilings severely deteriorated after 4–8 weeks causing an estimated cost of maintenance work of $4 million. The failure case investigation was carried out to ascertain the cause of the aforementioned coating defect and to propose a possible solution to the coating failure. An accepted method of repair has been proposed, and therefore to create a barrier system in the form of jacket material with anti corrosion wraps, protecting the underwater or splash zone pilings and other structural elements from further deterioration. The failure analysis results along with laboratory evaluation of the effectiveness of four different types of jacket materials will be addressed.

In-situ surface potential characterization of a cathodically polarized coating

The relevance of this study pertains to coating material performance in desalination and power plants and particularly during cathodic protection (CP) of coated steel piping network. Organic coatings find various uses in many industries and such coatings are used extensively in conjunction with CP by the petroleum and water industry for corrosion protection. One of the most common technical problems encountered by the inspector or engineers is that of micro-defects (pinholes) in coating and optimization of material selection. The nature of the surface electrochemical reactions associated with defects in these protective coatings and the ability of the Scanning Potential Mapping (SCM) to detect them is the concern of this investigation. The results indicate that this method can monitor the qualitative effectiveness of the cathodic depolarization CP. A demonstration problem is elaborated which gives information on the surface potential distribution on the exterior surface of the coal tar epoxy coated steel substrate with predefined defects. The results demonstrate the evolution with time of the SCM for the coated specimen, which shows initial increase of the surface potential. As the polarization potentials are concerned, the cathodic potential affected mainly their cathodic regions.