It has been believed for years by corrosion engineers
that ductile iron pipe does not corrode at the same rate
as steel pipe. This belief is primarily based on the assumption
that ductile iron pipe corrodes slower than steel pipe
because steel pipe generally contains less carbon than
While it may be true that ductile pipe usually corrodes
slower than steel pipe, this is assuming that the carbon
is uniformly distributed and that potential corrosive
hot spots do not exist. Recently, this assumption has
been found to be untrue. In fact, several recent pipeline
failures of ductile iron have indicated that corrosive
hot spots can exist which corrode at the same rate if
not faster than steel pipe.
Earlier arguments against conventional coatings being
used to coat ductile iron pipe was due to the dimple peened
surface of D.I. pipe. The adhesive of conventional coatings
did not contact the pipe surface, leaving air pockets
or voids under the coating which subsequently could corrode.
Earlier tapes were constructed of adhesives which were
hard and did not extrude or migrate into these surface
dimples. The TEK-RAP System allows the Inner Layer, which
is in contact with the entire pipe surface, to extrude
or mold into these surface irregularities and completely
bond to the pipe surface. The TEK-RAP Co-Extruded Ductile
Iron Coating System is designed to obtain 100% surface
adhesion and corrosion protection.
The TEK-RAP System contains stabilizers and inhibitors
designed to resist destructive effects of ultraviolet
light and soil oxidation to the polyethylene backing.
Ultraviolet light deterioration to the polyethylene backing
can begin if the coated D.l. pipe is left in a coating
plant storage yard or uncovered in an open burial. This
can cause unstabilized polyethylene to deteriorate and
lose its effective strength attributes within just a few
years service. TEK-RAP products are so reliable that we
offer them with the industry's only 40 year guarantee
when installed under TEK-RAP supervision, resulting in
drastically reduced maintenance costs.