Coating composition exhibiting reduced block, rapid dry rate an related methods

#Ductile iron pipe is commonly used for water distribution including potable water and sewage transport. The predominate raw material of pipe substrate is ductile iron, a spheroidized graphite cast iron. Like most ferrous or ferrite materials, ductile iron is susceptible to corrosion including galvanic, electrolytic corrosion, and/or microbiologically influenced corrosion. Thus, in the context of a ductile pipe application, it is advantageous to coat or line either the inner surface or outer surface or both of the pipe to mitigate corrosion concerns and extend life expectancy of the iron pipe insitu.

#Prior art attempts at lining and/or coating the pipe include polyethylene sleeving by wrapping the pipe in a loose sleeve of polyethylene. Sleeving inhibits the corrosion by physically separating the pipe from soil particles, and preventing direct galvanic corrosion, and provides a barrier that is impermeable to ground water and inhibits the diffusion of oxygen to the ductile iron surface, thereby limiting the availability of electrolytes that would accelerate corrosion. However, use of polyethylene sleeves or encasements has several drawbacks.

#Encasings can detach from iron pipes or develop holes or tears. Use of polyethylene sleeving is limited to certain soils or conditions including low moisture conditions, low soil contaminates and low soil resistivity. In addition, polyethylene is vulnerable to degradation by ultraviolet light, so storage, transport and transfer of the pipes requires cost intensive covered trucks and storage facilities.

#The aforementioned drawbacks are addressed by the invention, which encompasses emulsion compositions, coating layers formed from the emulsion compositions, and substrates, particularly metal substrates, that are coated with the coating layer. Also included within the scope of the invention are methods of reducing the rate of drying of the composition and methods of forming a coating that exhibits increased adherence to the substrate and/or a reduced incidence of blocking or “pull-off” during production. Once dried and formed, the coating layer provides to the substrate corrosion resistance, protection from physical damage, and/or reduction or prevention of contact of the substrate with materials adjacent to the substrate, for example, to prevent potable water from coming in contact with a metal surface of a metal pipe, vessel, or conduit. In addition, the rapid drying rate and increased adherence of the coating layer to the substrate provides a lessened incidence of blocking or “pull-off” during production, when the coated substrate is, for example, ductile pipe.

#The emulsion composition of the invention includes a barrier-forming material. Such material may be any known or developed in the art that can be emulsified and, when dried or cured, forms a barrier that is substantially impermeable to water and/or chemical liquids (aqueous or nonaqueous). In some instances it may be preferred that the barrier-forming material is a polymer, copolymer or polymer blend (hereinafter, referred to collectively as “polymer” or “polymers”). For example, it may be a thermosetting polymer or thermoplastic polymer, such as, for example, acrylic polymers, polyurethane polymers, and styrenated-acrylic polymers.

#As another alternative, the barrier-forming material may be an asphalt material, added to the composition in the form of a water-asphalt emulsion or as neat asphalt. Any asphalt may be selected; it may be preferred that the asphalt has a low oil content. For example, the water-asphalt emulsion composition of the invention composition of the invention may include a de-asphaltized “DA” grade asphalt. As is understood in the art, DA grade asphalt originates from “straight-run” asphalt that is formed from the distillation bottoms in crude oil refining. The DA asphalt is produced by solvent extracting remaining oil from straight-run asphalt.