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

2.B.12.1.1 Overview ...................................................................................................................... 95
2.B.12.1.2 Soil Corrosivity ........................................................................................................... 95
2.B.12.1.3 Preventing Soil Corrosion ......................................................................................... 96
2.B.12.2 Description of Damage ....................................................................................................... 96
2.B.12.3 Basic Data ............................................................................................................................ 97
2.B.12.4 Determination of Corrosion Rate ....................................................................................... 97
2.B.12.4.1 Corrosion Rate Equation ........................................................................................... 97
2.B.12.4.2 Establishing the Base Corrosion Rate ..................................................................... 97
2.B.12.4.3 Adjustment Factor for Soil Resistivity (Optional) ................................................... 98
2.B.12.4.4 Adjustment Factor for Temperature ......................................................................... 98
2.B.12.4.5 Adjustment Factor for CP and Stray Current Drainage .......................................... 98
2.B.12.4.6 Adjustment Factor for Coating Effectiveness ......................................................... 99
2.B.12.5 Nomenclature ...................................................................................................................... 99
2.B.12.6 References ...……………………………………………………………………………………..100
2.B.12.8 Figures ………………...………………………………………………………………………….102
2.B.13
CO2 CORROSION ...…………………………………………………………………………………...103
2.B.13.1 Description of Damage ...………………………………………………………………………103
2.B.13.2 Basic Data …...…………………………………………………………………………………...103
2.B.13.3 Determination of Corrosion Rate ….…………………………………………………………103
2.B.13.3.1 Calculation of the Corrosion Rate ……………………………………………………..103
2.B.13.3.2 Relative Humidity …………………………………………………………………………103
2.B.13.3.3 Base Corrosion Rate ……………………………………………………………………..104
2.B.13.3.4 Determining the pH ……………………………………………………………………….104
2.B.13.3.5 Determining the CO2 Fugacity .…………………………………………………………105
2.B.13.3.6 Determining the Flow Velocity ………………………………………………………….105
2.B.13.3.7 Adjustment for Inhibitors or Glycol ……………………………………………………106
2.B.13.4 Nomenclature …………………………………………………………………………………….106
2.B.13.5 Tables ……………………………………………………………………………………………...108
2.B.13.6 Figures …………………………………………………………………………………………….110
2.B.14
ATMOSPHERIC STORAGE TANK BOTTOM CORROSION ……………………………………..111
2.B.14.1 Description of Damage …………………………………………………………………………111
2.B.14.2 Basic Data ………………………………………………………………………………………...111
2.B.14.2.1 Soil-Side Corrosion Rate Equation …………………………………………………….111
2.B.14.2.2 Product-Side Corrosion Rate Equation ……………………………………………….111
2.B.14.3 Determination of Corrosion Rate ……………………………………………………………..111
2.B.14.3.1 Soil-Side Corrosion Rate Equation …………………………………………………….111
2.B.14.3.2 Product-Side Corrosion Rate Equation ……………………………………………….112
2.B.14.3.3 Combined Atmospheric Storage Tank Floor Corrosion Rate …………………….113
2.B.14.4 Nomenclature …………………………………………………………………………………….113
2.B.14.5 Tables ……………………………………………………………………………………………...114
2.B.14.6 Figures …………………………………………………………………………………………….117