When coating to be used as anode for CP for concrete, how can we measure resistaivity or conductivity of only coating??
Eddy current can be used to measure conductivity of non-magnetic coatings.
https://www.nde-ed.org/EducationResources/CommunityCollege/EddyCurrents/Applications/conductivitymeasurements.htm
Dear Arpit
Refer to the followings:
1-K.Habib,"Surface Resistivity/Conductivity of Different Organic-Thin Films by a Combination of Optical Shearography and Electrochemical Impedance Spectroscopy",OPTICAL REVIEW Vol. 20, No. 1 (2013) 59–64.
2-Khaled HABIB,” Measurement of Surface Resistivity/Conductivity of Different Organic Thin Films by a Combination of Optical Shearography and Electrochemical Impedance Spectroscopy”, OPTICAL REVIEW Vol. 20, No. 6 (2013) 500–503.
To measure the conductivity/resistivity, you need to use Wener 4 pin method by AC current. There a couple of different techniques available. ASTM B193–02 Standard Test Method for Resistivity of Electrical Conductor Materials is one of the methods.
Thank you everyone for answers.
Dear Miki,
When using wener 4 probe method, what should be the spacing between the electrodes and its depth, as it will possibly affect the resistance value. Moreover for measuring coating resistance, the applied surface should be plastic or cardboard.
Arpit, The pin spacing is based on the sample thickness. Because your sample is thin, I do not think the spacing is not big factor. I do no understand your question what is "applied surface"? You mean the base material to apply the conductive material? If so, the plastic is better because it is not influenced by any moisture.
I should tell you that when you test the conductive material as anode for cathodic protection, you need to consider many other factor, such as the resistivity based on the environment, time factor with amount of current discharging, the bonding to the substrate concrete with time, the anode-concrete interface with the current transfer, etc. If yo test without current, the test result is meaningless. The static resistivity measurement is only a small factor or the initial condition as the anode. The anode for CP system requires a minimum 30 to 40 years life with continuous operation (discharging CP current to the concrete electrolyte). If you use carbon based anode, you cannot accelerate the anode life test.
Miki, Thank you for clearing the doubt. I meant base layer only.
Yes I know all the above mentioned factors and I am testing my anode for them as well.
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