NACE CP2 – EXAM QUESTIONS AND ANSWERS Graded A+

NACE CP2 – EXAM QUESTIONS AND ANSWERS Graded A+ oxidation - ANSloss of electrons, positive charge atoms (anode) reduction - ANSgain of electrons, negative charged atoms (cathode) forms of corrosion - ANSuniform, crevice, galvanic (dissimilar metals) if two metals have to be couple then best to couple metals close together in the galvanic series, pitting, intergranular, selective leaching (dezincification, graphitization), velocity phenomena, environmental cracking (corrosion fatigue, hydrogen embrittlement, SCC (Carbonates/bicarbonates) High PH - ANSLow hydrogen, alkaline, easy polarization Low PH - ANShigh hydrogen, acidic, harder to polarize High oxygen/High Hydrogen concentration - ANSharder to polarize, work at the cathode only, called cathodic depolarizers. factors affecting corrosion - ANSA. anything that affects polarization. (temp. etc...) B. concentration cells (oxygen, temp, etc.) In an oxygen concentration cell, what is the anode? (i.e. the area with more or less oxygen?) In a metal ion cell, which area is the anode (i.e. the area with the greater of lower concentration)? C. Anaerobic bacteria (MIC) Absence of oxygen, depolarizer polarization - ANSa. corrosion current reduces with polarization b. polarization increases with CP current applied c. Occurs at surface of both anode and cathode. shielding - ANSa. shorted casings b. proximity of other structures c. reinforced concrete amphoteric materials - ANScorrode at low and high pH on potential - ANSnative + polarization + IR drop polarized potential (off) - ANSnative + polarization kirchoff's laws - ANSa. voltage (series circuits) b. current (parallel circuits) faraday's law - ANSW=KIT relates weight loss of metal in a corrosion cell with time and current flow. rate of corrosion - ANSdirectly proportional to current flow cathodic protection limitations - ANS-shielding issues -attenuation -interference -excessive current density -contact with other metals (shorts) measurement methods - ANStrue voltage reading voltmeter reading % error calculations effect of voltmeter resistance IR correction methods test stations - ANSallow electrical connection to structure for potential measurements and bonds. Spans allow current and direction (IR drop). inistall during construction pH - ANSmeasure of acidity(hydrogen ion concentration) high pH is alkalin