NACE CP 2 Concepts
The potential of a metal surface at a PH of 7 is -500 mV. What would be the potential of the same metal surface in a PH of 8?
-560 mV
Basic units of a rectifier
AC supply, circuit breaker, transformer, rectifying elements, meters, DC output terminals, fuses, surge protection
Metal surfaces in higher metal ion concentrations become more anodic or more cathodic?
Cathodic
Metal surfaces in higher oxygen concentrations become more anodic or more cathodic?
Cathodic
Metal surfaces in higher PH environments become more anodic or more cathodic?
Anodic
Metal surfaces in higher salt concentrations become more anodic or more cathodic?
Anodic
Metal surfaces in higher temperatures become more anodic or more cathodic?
Anodic
Anodic Interference
Current discharge, more negative structure potentials
Cathodic Interference
Current pickup, more positive structure potentials
When polarization increases, current and corrosion rate...
Decrease (when polarization is the control factor)
When movement in the electrodes and the electrolyte increases, polarization...
Decreases (and current increases)
When temperature increases, polarization...
Decreases (and current increases)
When there is an increase in cathodic metal ion concentration, polarization...
Decreases (and current increases)
What is used to prevent a reverse current at bonds
Diodes or reverse-current switches
Kirchoff's Law
E = IR
Nernst Equation
Expresses the exact electromotive force of a cell in terms of activities of products and reactants of the cell
Decrease in the potential difference between the anode and the cathode
Polarization
Faraday's law
Relates weight loss of metal in a corrosion cell with time and current
Corrosion can be expected at AC current densities at or above...
100 A/m^2
Voltages of ___ V AC are considered hazardous
15 V AC
Generally the lower the PH the _______ the CP current requirement
Greater
As oxidizers increase, the CP current requirement...
Increases
As temperature increases, the CP current requirement...
Increases
When there is an increase in anodic metal ion concentration, polarization...
Increases (and current decreases)
When current increases, polarization...
Increases (when current is the control factor)
