API RP 581 - 3rd Ed.2016 - Add.2-2020 - Risk-Based Inspection Methodology

RISK-BASED INSPECTION METHODOLOGY, PART 2, ANNEX 2.B—DETERMINATION OF CORROSION RATES 2.B-101
Temperature
°C °F
Multiplying Factor
<49 <120 1.00
49 to 104 120 to 220 2.00
>104 >220 1.00
Table 2.B.12.5—CP Effectiveness Factors
CP Measurement Practices
No CP on structure (or CP exists but is not regularly tested per NACE RP0169) and CP
on an adjacent structure could cause stray current corrosion
Multiplying Factor
10.0
No CP 1.0
CP exists, but is not tested each year or part of the structure is not in accordance with
any NACE RP0169 criteria
CP is tested annually and is in accordance with NACE RP0169 “on” potential criteria
over entire structure
CP is tested annually and is in accordance with NACE RP0169 polarized or “instant-off”
potential criteria over entire structure
0.8
0.4
0.05
Table 2.B.12.6—Calculating the Total Coating Effectiveness Factor
Coating Type
Base
Factor for
Coating
Type
Age > 20
years
Multiplying Factors
Maximum Rated
Temperature Is
Occasionally Exceeded
Coating
Maintenance Is
Rare or None
Fusion bonded epoxy
Liquid epoxy
Asphalt enamel
Asphalt mastic
Coal tar enamel
1.0
1.0
1.1
1.2
1.5
2.0
1.1
1.5
Extruded polyethylene with mastic or rubber 1.0 1.2 3.0 1.5
Mill applied PE tape with mastic 1.5 1.2 3.0 1.5
Field applied PE tape with mastic 2.0 2.0 3.0 1.5
Three-layer PE or PP 1.0 1.2 2.0 1.2