A two-part coating system comprises a first part comprising one or more aliphatic polyisocyanates, optionally blended with one or more “amine reactive” resins and/or non reactive resins, and a second part comprising one or more aromatic polyamines optionally blended with one or more oligomeric polyamines, such that the two parts, when mixed together and applied to the internal surfaces of pipelines, form a rapid setting impervious coating suitable for contact with drinking water.