Coatings coal tar

The maximum protected length 2 L is given in Fig. 10-1 and the required protection current in Fig. 10-2. For pipelines with carefully mill-applied PE and excellent field-applied coating of the girth weld area, the protection current densities lie between 1 and 3 jJ.A m With carefully buried pipelines with bitumen (or coal tar) coating, the protection current densities lie between 10 and 30 jUA mr. ... 

The choice of voltage for use with a holiday detector depends on the thickness and type of coating applied to the structure. As a guide, in the case of pipelines, a voltage equivalent to approximately 5 kV/mm thickness is used in testing a coal-tar coating. 

The AWWA C-203 Standard remains a widely used specification suitable not only for the materials, but also for their associated reinforcing wraps and application procedures. The standard has been regularly updated. Hot-applied asphaltic and coal-tar coatings with their priming systems are now well classified, described and specified in BS 4164 1967 (coal tar) and BS 4147 1967 (asphalt), but no guidance is given in these specifications to application procedures. 

Distribution Systems. A substantial amount of contamination of drinking water can occur while the water is in transit to the consumer after treatment. Pipes are made of copper, galvanized iron, asbestos-cement, lead, or plastic, and often polymeric or coal tar coatings are used. All of these are capable of contributing contaminants to the water, especially if the water is corrosive. Lead, copper, cadmium, and polynuclear aromatic hydrocarbons in finished water are primarily problems of water distribution and not source water contamination. Physical deterioration of the distribution system can also permit biological contamination to occur during transit. 

Asbestos, metals, and vinyl chloride monomers from certain types of poly(vinyl chloride) piping and PAHs from coal-tar coatings. 

They are used mainly as curing agents for solvent-based coatings, epoxy coal tar coatings, putties, adhesives and solvents. Polyamide-cured epoxy coatings have the drawback of being somewhat softer and less chemically resistant than other coatings. 

Triple A. [Zophar Mills] Asphalt and coal tar coatings. 

Epoxy/coal-tar coating, in contact with sea-water... 

A nearly complete recovery of the coating s volume resistivity is measured, if an epoxy coal-tar coating after about fourteen days of contact with seawater is immersed in crude oil (Figure 5.18). This indicates that the seawater absorbed is nearly completely leached out by the crude oil i.e. crude oil absorps seawater considerably stronger than the epoxy coal-tar coating does. 

Equation 5.28 results in a relaxation time of about 50 seconds for the epoxy coal-tar coating as such. This value decreases to about 0.2 seconds after contact of the coating with seawater. The relaxation time of the epoxy coal-tar system remains higher than the relaxation times of 0.018 s. to 0.00018 reported for different crude oils [28], even after prolonged contact with seawater. 

In some cases, coal tar has been used, but these pose health hazards and oily organic residues given off by coal tar coatings limit their use. Steel pipes are used for about 4% of the US transmission water lines. The most common corrosion control methods for external corrosion of steel pipes are coatings or coatings and CP. 

Uses Surfactant additive, rTKrdifier for day-stabilized coal tar and asphalt emulsions (improves adhesion, wear resist., water resist., and speeds dry time of coal tar coatings)... 

Coal tar, or pitch, is the black organic resin left over from the distillation of coal. It is nearly waterproof and has been added to epoxy amine and polymide paints to obtain coatings with very low water permeability. It should be noted that coal tar products contain polynuclear aromatic compounds, which are suspected to be carcinogenic. The use of coal tar coatings is therefore restricted or banned in some countries. 

When coal is heated to 1095°C in the absence of air, it decomposes into gas and coke. Coal tar is formed and gas is condensed. All coal tar coatings are subjected to degradation by ultraviolet radiation and cracking. 

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