Royston A-51 & A-51 Low VOC

Thixotropic brush applied coal tar coating


Royston A51 is thixotropic, brush applied coal tar coating for below grade applications. A time proven coating technology for providing corrosion protection to metal fittings, flanges, valves, tanks, mechanical couplings, anode connections and other difficult and irregular configurations. It is also designed to protect concrete surfaces from adverse environments.

The A-51 Low VOC has a VOC content of <327 g/l (2.73 lb/gal) and shares all other properties with the regular A-51.

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Classified by a UN:

•  High electrical resistivity designed to protect underground steel pipes, tanks and other structures against corrosion particularly in soils saturated with gasoline and other contaminants.

•  Excellent above ground coating for protection against severely corrosive atmospheric fumes and against moisture and salt in coastal areas.

•  Bonds firmly to steel surfaces without the use of primer.

•  Endures over a long period of time because of its resistance to soil stress and to attack by alkalis, acids, salts, moisture and gasoline.

Surface Preparation

Surfaces should be dry and cleaned of all rust, scale, soil, mud, oil, grease and other contaminants in the field by wire brushing. Sand blasting or chemical treatment may be more convenient for in-plant surface preparation. No primer is required.

Application Procedure

Royston Roskote A-51 should be stirred thoroughly before using. Thinning is not required except for cold spray at temperatures below 60oF. The heavy mastic is specially formulated to obtain a thick protective coating. If excess thickening occurs because of solvent losses from opened containers, restore to original viscosity with Royston Thinner No. 70 or a mixture of equal parts of toluene and MEK.

Apply cold by brush, glove or booster-pump spray. Apply to cover 65 to 70 square feet per gallon, which will provide a dry film thickness of about 12 mils per coat. When the first coat has dried to the touch, which will usually require less than an hour, apply a second coat at the same thickness.


Brush and Glove Application

Apply liberally with a generous amount at all times. It should never be applied thin. However, a wet film thickness of .040 inches is maximum per coat to reduce the possibility of mud cracking.

Spray Application

Booster type spray equipment is required because of Royston Roskote A-51’s heavy consistency. It may be sprayed with minimal thinning at temperatures above 60 F. It is usually necessary to thin with one quart of thinner to each five gallons of Royston Roskote A-51 in temperatures below 60oF. Use high boiling (250oF) mineral spirits for spray thinning.

Either air type or airless spray equipment commercially available from several manufacturers may be used. The following equipment procedures have provided satisfactory results, but alternates may be equally successful.

Airless Spray

Good spray results can be obtained with an airless high volume 10:1 pump with air cap assisted atomization, e.g., Binks Model 98-792 outfit or equal.



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