Resistance of Anode

8/18/2019 Resistance of Anode

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Anode Resistance to Earth

Single - Multiple - Vertical - Horizontal

Anode Resistance to Earth

Soil Resistivity =ohm-cm

Anode Length =feet

Anode Diameter =inches*

Multiple Anodes

(Leave lan! for single anode configuration"

#umer of Anodes =

Anode Spacing =feet

$ori%ontal &onfiguration

(Leave lan! for vertical anode configuration"

Anode Depth =feet**

Resistance =ohms

This calculator can be used to calculate resistance to coke breeze or resistance of coke column to eartused to calculate resistance of coke column to earthresult may be a reasonable approximation of totalgroundbed resistance; however, factors such as cabresistance and anode to coke resistance are not inc The program converts inches to feet.

** node depth is doubled by the program

Single 'ertical Anode

ormula )sed

Where

R = resistance in ohms

L= anode length in feet

d = anode diameter in feet

= resistivity in ohm-cm

ln is the natural logarithm function

Multiple 'ertical Anodes in +arallel

ormula )sed

Where


L = anode length in feet

N = the number of anodes

S = anode spacing in feet


!eset


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N = the number of anodes = 1 = resistivity in ohm-cm


Multiple $ori%ontal Anodes

ormula )sed

Where


L = anode length in feet

S = twice the depth of anode in feet

N = the number of anodes


= resistivity in ohm-cm


Anode Requirement Calculation

The following material was researched and was submitted as a guideline for calculating the requirements of sacrificial anodes for your

application:

• a) Calculate the AREA to be protected.

• b) The national Association of Corrosion Engineers, NACE standard R!"#!$% states the requirement of a

polari&ation to !".'() *ersus Cu!saturated Cu+-, for protection of a steel structure in a neutralen*ironment. This is nown as the /AR01E2 TENT0A/. The sacrificial anode system design requiresthe current density to achie*e this potential.

• c) The C3RRENT 2E4AN2 is calculated by multiplying the required current density by the area. Note that

it is important to consider the en*ironment that the metal is e5posed to since the 6current demand6 may

*ary with different combinations.

• d) The ne5t step is to determine the total required mass of the sacrificial anodes. The AN2E

CN+34T0N is determined from tabulated consumption rates for the calculated current demand.

• e) 2i*ide the total required mass by an appropriate quantity of anodes that will create a uniform current

distribution o*er the entire area to be protected.

• f) Calculate the AN2E RE+0+TANCE from the distribution and quantity of the sacrificial anodes.

• g) 7rom the anode resistance, R and *oltage, ) from the selected sacrificial anodes, the 2E+08N 3T3T

C3RRENT, 0 is calculated using the following formula: 0 9 )R


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Note that the output current should meet or e5ceed the required current from step C.

+A4/E CA/C3/AT0N

o 1) Assume that the calculated Area of the ship;s hullsteel surface to be protected is: -'"m.

?ewes, Cathodic rotection Theory and ractice, ). Ashworth and C.@./. ooer, eds., >ileyB?orwood, Chichester, >est +usse5, #%'$D 7or this e5ample, we will assume a current density

requirement of (mAm


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luminum "rone /*),+0

.astelloy */active0 nconel )('/active0 2itanium/active0

Lead32in Solder

Lead

2in

nconel )## /active0 Nic4el /active0

)#5 Ni 1'5 *r /active0

,#5 Ni (#5 *r /active0

.astelloy " /active0

Naval "rass /*&)&0$ 6ellow "rass /*(),0

Red "rass /*(%#0$ dmiralty "rass /*&&%0

*opper /*1#(0

Manganese "rone/*)+'0$ 2in "rone/*7#%$ 7#'0

&1#$ &1) Stainless/passive0 8hosphor "rone/*'(1$ '(&0

Silicon "rone /*)'1$ )''0

Nic4el Silver /* +%($ +%'$ +&'$ +'($ +'&$ +'+$ +)'$ ++#$ +7&*upro Nic4el 7#-1#

*upro Nic4el ,#-(#

&%# Stainless /passive0

*upro Nic4el +#-%#

Nic4el luminum "rone /*)%#$ )%(0

Monel #$ 9'##

Silver Solder

Nic4el /passive0

)#5 Ni 1'5 *r /passive0

conel )## /passive0

,#5 Ni (#5 *r /passive0

*hrome ron /passive0

%#($ %#%$ %#&$ %(1$ %&+ Stainless /passive0

%1)$ %1+ Stainless /passive0

*arpenter (#*b-% Stainless /passive0$ ncoloy ,(' /passive0

Silver

2itanium /passive0$ .astelloy * : *(+) /passive0

;raphite

!irconium

;old

8latinum

&A.$,DE E#D (Least Li!ely to &orrode"

Anodic nde! Chart

>hen dissimilar metals come in contact, gal*anic compatibility is managed by the selection of finishes and plating to protect the base

materials from corrosion.

• ?arsh en*ironments: not more than ".#( ) difference


5/6

• Normal en*ironments: not be more than ".


6/6

luminum$ cast alloys other than silicon type$ cadmium$ plated and chromate #

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Resistance of Anode