1. Corrosion Management on Pipeline with Cathodic Protection
Ilmu Bahan dan Korosi

2. Outline Pipeline Risks and Corrosion
Cp Technique : Galvanic Sacrificial Anode (Principle, Installation)
Cp Technique : Impressed Current (Principle, Installation)
Case Study : Sacrificial Anode
Case Study : Impressed Current

3. Risks on Pipeline RISK = PROBABILITY x SEVERITY
The product of the frequency with which an event is anticipated to occur and the consequence of the event outcome.
RISK = PROBABILITY x SEVERITY

4. Risks on Pipeline
PRESSURE
DROP
LEAKAGE
CORROSION

5. Corrosion Control Coating : insulation
Cathodic Protection: DC current injection towards pipeline, result: pipeline is “shifted” as cathode.
Sacrificial anode
Impressed current

6. Galvanic Sacrificial Anode - Principle
Metal Driving voltage (Vd)
Negative Vd = active metal =tendency to corrode
Pipeline: connected with active metal
Anode: Mg, Zn Cathode: pipeline
Corrosion on Mg, Zn hence “sacrificial”

7. Galvanic Sacrificial Anode-Principle
Material
Driving Voltage (V)
Silver (Ag/Ag+)
(cathodic)
Copper (Cu/Cu2+)
+0.34
Water (O2+H20+4e- = 4OH-)
+0.401
Hydrogen (H2)
(reference)
Iron (Fe/Fe2+)
-0.44
Zinc (Zn/Zn2+)
-0.76
Magnesium (Mg2+)
(anodic)

8. Galvanic Sacrificial Anode-Installation
(Source: Peabody’s Control of Pipeline Corrosion)

9. Galvanic Sacrificial Anode-Installation
(Source: Peabody’s Control of Pipeline Corrosion)

10. (Source: Peabody’s Control of Pipeline Corrosion)
Impressed Current
(Source: Peabody’s Control of Pipeline Corrosion)
Minimum potential: -0.85V
Reference electrode: Copper Sulfate

11. Galvanic Sacrificial Anode-Design
Calculate total area to be protected (Ap)
Determine the current density (ρ)
Calculate total protection current (Itot = ρ .Ap)
Calculate R per anode : R = f(d,l,ρ)
Calculate Ia per anode : (Vd-0.85/R)
Calculate total anode needed :
Initial : N=Itot/In
Lifetime: N = f(mass,lifetime,A/poundyear)

12. Impressed Current-Principle
Rectifier
Variable voltage, variable current
Higher current density (> 1 A)
Higher soil resistivity (> 104 Ωcm)

13. Impressed Current-Installation
Types of anode:
Graphite : big CR (pound/A/year)
High Silicon Cast Iron : medium CR
Platinum & niobium : small CR
Rectifier rating:
Voltage, Amperes, Watt, Freq.
Cooling System : Air, Oil
Efficiency
CR: Consumption Rate

14. Impressed Current - Installation
(Source: Peabody’s Control of Pipeline Corrosion)

15. Impressed Current - Design
Calculate total area to be protected (Ap)
Determine curent density (ρ)
Calculate total protection current (Ip)
Calculate total anode needed (N)
Initial
Lifetime
Calculate total anode resistance (Rtot = f(N,ρ,d,L,spacing))
Calculate rectifier specification (Vdc, Idc, Pdc = f(Rtot,Ip)

16. Pipeline Cathodic Protection– Case Study

17. Galvanic Sacrificial Anode – Case Study
Variabel
Nilai
Pipe Diameter (d)
a. 2 inch = m
b. 1 inch = m
Pipe Length (l)
a. 2 inch pipe: 300m
b. 1 inch pipe: 1300m
Soil Resistivity (average)
4500 Ωcm
Current Density (ρ)
9mA/sqmm
Type of Anode
Magnesium, weight 9 pon, r = 8.89cm, l = 53.54cm
Coating efficiency (n)
50%
Lifetime
20 years

18. Galvanic Sacrificial Anode – Case Study
Step 1: surface area of pipeline
Step 2: total protection area
Step 3: total protection current

19. Galvanic Sacrificial Anode – Case Study
Step 4: Anode resistance (Dwight’s Equation)
Step 5: Current per Anode

20. Galvanic Sacrificial Anode – Case Study
Step 6: Total Number of Anode
Initial
Lifetime
Selected number of anodes: 31.

21. Galvanic Sacrificial Anode – Case Study
Step 7: Distribution and Layout
Distribution
Layout
Type of Pipe
Effective Surface (Ac)
Number of Anode (Ac/A)
Diameter 2inch (0.0508m)
Diameter 1inch (0.0254m)
Total 31

22. Impressed Current Case Study
Variabel
Value
Pipe Diameter (d)
6 inch = 0,1524 m
Pipe Lengyth (l)
6800 feet = 2072 m = 2,072 km
Soil Resistivity (average)
2000 Ωcm
Current Density (ρ)
30mA/sqmm
Type of Anode
Stated in next section
Coating Efficiency (n)
50%
Coating Impedance
25000Ω/m2
Maximum Groundbed Resistance 2Ω
Lifetime
15years

23. Impressed Current Case Study
Step 1: surface area of pipeline
Step 2: total protection area
Step 3: total protection current
Step 4: determine type of anodes
Iron Silicon Chromium. Weight: 110 pon, cross section 4 sqft (0,371m2),
diameter 10 inch (0,833 feet = 2,54cm), length 84 inchi (7 feet = 20,32cm)

24. Impressed Current Case Study
Step 5: total number of anodes
Current limit (silicon: A/m2)
Lifetime
Total anodes: 4.

25. Impressed Current –Case Study
Step 6: groundbed resistance calculation
Resistance limit: 2Ω (to limit rectifier’s spec)
Spacing: S = 30 feet , Anode Length: L = 7 feet
Anode Diameter: D = feet
Groundbed resistance is below limit.
If not, choose longer spacing.

26. Impressed Current - Principle
Step 7: rectifier specification
Specification: 21VDC, 302W .
Final Results:
Anodes : Iron Silicon Chromium, 4 anodes.
Rectifier : 21VDC, 302W.