NACE CP3 - Chpt 1. Mechanisms of Corrosion Questions & Answers Solved 100% Correct!!

Nerst Equation - CORRECT ANSWER-A metal electrode potential is a function of the metal ion activity, which is related to metal ion concentration. As metal ion concentration increases (M^n+) the potential becomes more electropositive. At 1 molar solution of metal ions. Em = ....... ln(a^Mn+/a^Mo) Cathode Reaction - CORRECT ANSWER-Reduction Reaction Anode Reaction - CORRECT ANSWER-Oxidation Reaction SHE to CSE - CORRECT ANSWER-+316 mV SHE to SSC (SJ) - CORRECT ANSWER-+256 mV SHE to ZRE - CORRECT ANSWER--800 mV SSC to CSE - CORRECT ANSWER-+60 mV Corrosion Zone - CORRECT ANSWER-Fe0 -> Fe++ + 2e- (soluble - reaction can keep occuring) Immunity to Passive - CORRECT ANSWER-Fe0 + 2H2O -> Fe(OH)3 + 2H+ + 2e- (insoluble - builds up at the interface) Corrosion to Passive - CORRECT ANSWER-Fe++ + 3H2O -> Fe(OH)3 +3H+ + 1eMore Active (+ or -) - CORRECT ANSWER-Electronegative - Less Noble Less Active (+ or -) - CORRECT ANSWER-Electropositive - More Noble In non-aerated soils and waters the typical reduction reaction is ... - CORRECT ANSWER-Reduction of Hydrogen H+ + e- -> Ho In aerated soils and waters the typical reduction reaction is ... - CORRECT ANSWERReduction of Oxygen O2 + 2H2O + 4e- -> 4OHCorrosion Current in a Corrosion Cell - CORRECT ANSWER-Direction of positive charges flow. Anode to Cathode through the electrolyte and from cathode to anode in the metalic path. Define Polarization - CORRECT ANSWER-The electrical energy used up in the transfer of charge across the respective metal/electrolyte interfaces. Build up of product. Increase in polarization is a slowing down of the charge transfer reaction. Faraday's Law - CORRECT ANSWER-Material lost at the anode or deposited at the cathode is a function of atomic weight of the metal number of charges transferred corrosion current