Polypropylene (PP)
Polyethylene (PE)
Tetrafluoroethylene (PTFE)
Fluorinated ethylene propylene (FEP)
Perfluoralkoxy (PEA)
Ethylene-tetrafluoroethylene (ETFE)
Ethylene-chlorotrifluorethylene (ECTFE)
These materials are capable of providing aw ide range of corrosion
resistance. Table 6.17 lists the general area of corrosion resistance for eachof
the thermoplasts, but it is only ag eneral guide.T he resistance of al ining
material to as pecificcorrodentshould be checked.
These materials areused to line vessels as well as pipes and fittings. When
vesselsa re lined, the linings, with the exception of plasticizedP VC,a re
fabricated from sheets tock that must be cut, shaped, andj oined. Joining is
usually accomplished by hot-gasw elding. Several problems exist when a
thermoplastic lining is bonded to ametal shell, primarily the large differences
in the coefficiento ft hermal expansion and the difficulty of adhesion. If the
vessel is to be used under ambient temperature, such as as torage vessel,
the problems of thermalexpansiondifferences are eliminated. However,the
problem of adhesion is still present. Because of this, many linings are
installed as loose liningsinthe vessel.
Techniques have been developed to overcome the problem of adhesion that
make use of an intermediate bond. Oneapproach is to heat the thermoplastic
sheett hen impress it into ones urface afi ber cloth or nonwoven web. This
provides half of the bond.Bonding to the metal surface is accomplished by
the use of an epoxy adhesive that will bond to both the fiber and the metal.
Welding techniques for joiningt he thermoplastic sheets are very critical.
Each weld must be continuous, leak-tight, and mechanicallys trong. It is
TABLE 6.17
General Corrosion Resistance of Thermoplastic Lining Materials
Material
Strong
Acids
Strong
Bases
Chlorinated
Solvents
Esters and
Ketones
Strong
Oxidants
PVC (type 1)
FF
PP
P
CPVC
FF
FP
P
PVDF
EP
EP
E
PP
GE
PF
P
PE
FG
PP
E
PTFE
EE
EE
E
FEP
EE
EE
E
PFAE
EE
EE
ETFE
EE
EE
E
ECTFE
EE
EE
E
E, excellent; G, good; F, fair,P ,poor.
Corrosion of Linings and Coatings
344
CAT8247—CHAPTER 6—6/10/2006—12:30—SRIDHAR—XML MODEL B–pp. 287–402
Polyethylene (PE)
Tetrafluoroethylene (PTFE)
Fluorinated ethylene propylene (FEP)
Perfluoralkoxy (PEA)
Ethylene-tetrafluoroethylene (ETFE)
Ethylene-chlorotrifluorethylene (ECTFE)
These materials are capable of providing aw ide range of corrosion
resistance. Table 6.17 lists the general area of corrosion resistance for eachof
the thermoplasts, but it is only ag eneral guide.T he resistance of al ining
material to as pecificcorrodentshould be checked.
These materials areused to line vessels as well as pipes and fittings. When
vesselsa re lined, the linings, with the exception of plasticizedP VC,a re
fabricated from sheets tock that must be cut, shaped, andj oined. Joining is
usually accomplished by hot-gasw elding. Several problems exist when a
thermoplastic lining is bonded to ametal shell, primarily the large differences
in the coefficiento ft hermal expansion and the difficulty of adhesion. If the
vessel is to be used under ambient temperature, such as as torage vessel,
the problems of thermalexpansiondifferences are eliminated. However,the
problem of adhesion is still present. Because of this, many linings are
installed as loose liningsinthe vessel.
Techniques have been developed to overcome the problem of adhesion that
make use of an intermediate bond. Oneapproach is to heat the thermoplastic
sheett hen impress it into ones urface afi ber cloth or nonwoven web. This
provides half of the bond.Bonding to the metal surface is accomplished by
the use of an epoxy adhesive that will bond to both the fiber and the metal.
Welding techniques for joiningt he thermoplastic sheets are very critical.
Each weld must be continuous, leak-tight, and mechanicallys trong. It is
TABLE 6.17
General Corrosion Resistance of Thermoplastic Lining Materials
Material
Strong
Acids
Strong
Bases
Chlorinated
Solvents
Esters and
Ketones
Strong
Oxidants
PVC (type 1)
FF
PP
P
CPVC
FF
FP
P
PVDF
EP
EP
E
PP
GE
PF
P
PE
FG
PP
E
PTFE
EE
EE
E
FEP
EE
EE
E
PFAE
EE
EE
ETFE
EE
EE
E
ECTFE
EE
EE
E
E, excellent; G, good; F, fair,P ,poor.
Corrosion of Linings and Coatings
344
CAT8247—CHAPTER 6—6/10/2006—12:30—SRIDHAR—XML MODEL B–pp. 287–402