When it comes to corrosion protection, what is the major difference between concrete pressure pipe and ductile iron pipe?
Concrete pressure pipe is protected by mortar coating which provides a high alkaline environment that passivates all steel components. The 1-inch thick mortar coating not only provides a rugged physical barrier but also provides the chemical protection necessary to resist corrosion in aggressive soils. Ductile iron pipe is a metallic product that comes with no reliable exterior coating. As such, ductile iron pipe lacks the chemical and physical protection necessary to effectively protect the pipe. Baggies (i.e., polyethylene encasement) which are occasionally specified on ductile iron projects to provide corrosion protection, have been found to be ineffective in protecting ductile iron pipe. This is due to two reasons: a) difficulty of installing the baggies without damage making ductile iron with baggies more susceptible to corrosion in areas around the torn encasement; b) difficulty of monitoring or applying an effective cathodic protection system to protect areas of damaged ductile
