Coal tar epoxy

Asphalt, unmodified Coal tar Coal tar— epoxy Coal tar— nretlianes Epoxy phenolic- baked Epoxy amine- cnred Epoxy ester Fnrfnryl alcohol Phenolics, baked Polyesters (nnsati i-rated) Polyvinyl cliloracetates Vinyl ester Urethanes Vinylidene cliloride Clilorinated rubber... 

Vinyl tars These are a combination of vinyl resins and selected coal tars. They are claimed to be similar to the two-pack coal tar epoxies but with the advantages that they are a single pack, not dependent on temperature for curing, and are easy to re-coat at any stage. 

Their disadvantages, particularly in comparison with coal tar epoxies, include the fact that they are limited in film thickness per coat and therefore require multi-coated application. They have a higher solvent content and therefore there is an increasing risk of solvent entrapment, and the slower cure may limit their use in a tidal zone. The best use is for immersed conditions. 

Two-pack epoxies Coal tar epoxies Two-pack urethanes Moisture-cured urethanes... 

Coal tar epoxies These are a combination of epoxy resins and selected coal tars. Properties can vary, depending on the coal tar-to-epoxy ratio. The ideal compromise appears to be approximately 50/50. Coal tar epoxies are only available in black or dark brown. They cost less than straight epoxies and generally have better wetting properties, so they can be used on slightly less than perfect surface preparation. There are similar re-coating problems as for the two-pack epoxies. 

Two-pack epoxy Section 12.3.3. These are widely used to give the maximum protection to concrete surfaces, floors and walls. They can be applied as relatively thin coatings by spray or as thick epoxy surfaces applied by trowel. In all cases, the application must be preceded by adequate surface preparation (see Section 12.6.1). To allow maximum penetration into the concrete the first coat must have a low viscosity. Coal tar epoxies are used where protection is the main requirement. 

Suitable paints for use underwater include vinyl resin systems, coal tar paints over inorganic zinc-rich primers, and some coal-tar epoxy primers have also proved themselves Special paints are available for application under water, e.g. epoxy modifications with polyamides. 

The zinc silicate, epoxy and coal tar/epoxy coatings are still used. Coal tar epoxies are used for crude oil tanks, sometimes on all the interior surfaces but more often for a) the bottom of the tank and about 2 m up the sides, b) the top of the tank and about 2 m down the sides, and (c) other horizontal surfaces where seawater ballast may lie. These partly coated tanks are frequently also fitted with cathodic protection to prevent corrosion of the uncoated areas when seawater ballast is carried. The pure epoxy or coal tar epoxy coatings applied in bulk cargo tanks used for the carriage of grain must be approved by the North of England Industrial Health Service, or by similar independent authorities in other countries. 

The thickness and water resistance of the normal air-cured film can now be much improved by the incorporation of suitable coal-tar pitch material. A typical coal tar/epoxy coating material would be constituted as follows ... 

Unless some external shock source was employed, it was found that molten aluminum had to reach the vessel bottom before an explosion could occur. In these cases, oiganic coatings and paints (except silicones) prevented explosions. Many coatings were studied (see, in particular, Hess et al., 1980) and, when evaluated on many tests of applicability, durability, and nonexplosive characteristics, it was recommended that epoxy, coal-tar epoxy, and bituminous paints be used. Silicone, graphite, and inorganic coatings, in general, did not prevent explosions. 

Coal tar epoxy and plasticized chlorinated rubber laquer coated on mild steel were studied by Scantlebury et al (28). Impedance plots show a gradual decrease in the value of R t and the onset of Warburg-type behavior with increasing Immersion time in 3 weight percent sodium chloride solution. Appearance of an inductive loop when the coal-tar epoxy had a pin-hole was clearly demonstrated. 

The best generic coatings for carbon steel that may be surrounded by wet insulation in the 140° to 250° F (60° to 120° C) range are the epoxy phenolic and the amine-cured coal tar epoxy formulations. 

Tank bottom corrosion is a function of the water layer that exists on the bottom of most tanks. The presence of sulfate-reducing bacteria, characterized by shiny pits, is more of a problem in heavy stocks because oxygen cannot reach the bottom. The most common way to control tank bottom corrosion is to drain the water from the tank bottom periodically. Both epoxy and polyester coatings reinforced with chopped glass fiber have been used successfully in places where severe corrosion has occurred. For new tanks in which corrosion is expected, coal-tar epoxy is usually specified for the bottom. Corrosion of the underside of the tank bottom does not usually occur if a proper oH and sand base is used. Cathodic protection is used when water cannot be prevented from contacting the underside of the tank bottom. 

Solid adducts Isolated amine products, in particular, offer advantages such as low colour, low free amine content and low irritation potential they also provide non-yellowing, bloom-free films with good chemical and solvent resistance Amine adducts solvent-based, two-pack coatings, e.g. primers, finishes and coal tar epoxy coatings... 

Coal tar epoxy coatings are formulated by using liquid or solid epoxy resins. A variety of curing agents can be used for instance amines, amine... 

Coal tar-epoxy coatings are resistant to a wide range of chemicals and chemical solutions, including freshwater, seawater, distilled water, sewage, detergents, dilute mineral adds and alkalis, barnacle growth, exhaust... 

Particular applications of coal tar-epoxy coatings related to concrete and metal protection include tank linings, pipes, foundations in aggressive soils, manholes, sewage works, effluent plants, chemical processing plants and dock and harbour installations. 

Coal tar-epoxy coatings are not suitable for use as a tank lining material for gasoline and other hydrocarbon fuels as they tend to discolour clean fuel by a leaching process (Sherman et ai, 1982). 

General properties of coal tar-epoxy coatings are listed in Table 3.4. Legislation in many countries is leading towards the search for suitable alternatives to coal tar, which is considered to be carcinogenic. Albino coal tar modifiers appear to be suitable for the job (Hunt and Ashcroft, 1994). 

Cementitious Chlorinated Rubber Coal Tar Epoxy Epoxy... 

Table IX gives a typical formulation for coal tar epoxy. It contains approximately 30% epoxy and 25% coal tar. This type of coating will perform better than either the pure coal tar or the pure epoxy coatings in several applications. Because of the relatively low cost of coal tar pitch, the raw material cost is significantly less than for a pure epoxy.

Table IX. Typical Formulation (Coal Tar-Epoxy Coating)...

Mono-Card. [XymaX] Single-conqx)-nent coal tar epoxy teplacemott... 

Construction Materials. Carbon steel is used for most of the plants in some areas it is protected against rusting by a coal tar epoxy coating. The water outlet fine of the sulfur melter is stainless steel. No notable corrosion has occurred. 

If heavy fuel oil is fired, alloy studs with washers are provided and protected with ceramic fiber putty to prevent corrosion by metal slags. When high sulfur fuels are fired, the shell interior walls should be protected with a high temperature coating of sodium silicate or coal tar epoxy. Another method is to apply a thin layer of insulation to the exterior of the vessel to maintain the vessel s wall temperature safely above the dewpoint. A third approach is to impale a thin sheet of aluminum or alloy sheet steel on the studs at the midpoint of the ceramic insulation to reduce th flow of sulfur containing gases to the vessel s I.D. 

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