A spray lining is a polyurethane or polyurea based coating that is applied to to the inner walls of a host pipe via a rotating spray head. This technique is commonly used in trenchless construction to rehabilitate pipes in-situ without the need for excavation. A spray lining is typically applied when a pipeline has become compromised by corrosion to prolong the service life of a pipe. Spray lining is also known as spray-in-place pipe (SIPP) lining.