Multiple Choice Questions on

Cathodic Protection

Questions 6 - 10

Page 2 of 4

6.

In cathodic protection by impressed current system, a backfill known as coke breeze, is used.  This backfill has which one of the following functions?

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It increases the anode-to-earth resistance

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It decreases the effective size of anode

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It extends the life of the anode

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It increases the rate of consumption which is beneficial

7.

As a rule, for the cathodic protection system to work, the circuit resistance, Rc = Rs + Rlw + Rgb  (Rs = resistance of structure to electrolyte, Rlw  = lead wire resistance, (Rgb = ground-bed resistance) must be

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greater than the maximum allowable circuit resistance, Rmax=Emax/Imax

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must not be greater than Rmax

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must be equal to Rmax

8.

The driving potential of an impressive current anode is determined by

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ED = (VoltON - VoltOFF)/ION

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ED = EA (solution potential of anode material) - EP (potential of the structure)

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an electrical connection is made between the two half cells

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oxygen at 1 atmosphere is introduced in the two half cells

9.

Which one of the following conditions is most appropriate for a practical galvanic anode requirement?

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The potential between the anode and cathode must be equal to the difference of potential between the anodes and cathodes on the structure

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The potential of anode-cathode cells must be significantly lower than the potential between the anode and the corroding structure

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The anode-cathode potential difference on the corroding structure must be larger than the anode-structure potential

10.

Which of the following indicates that the structure to be protected is receiving current?

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 A potential change of -0.85 volts vs Cu-CuSO4

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 A potential change of -0.3 volt in the negative direction

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 A potential change of -1.2 volt in any direction

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 A potential change of -0.90 volt in the anodic direction