NACE 2 CBT Study Guide Questions with Verified Solutions Latest Update

NACE 2 CBT Study Guide Questions with Verified Solutions Latest Update Corrosion is established as a what kind of current? - Answer -Direct Current All corrosion of iron at normal ambient conditions is ________________ ____________ - Answer -an electrochemical process Define, E=IR - Answer -E is driving voltage, I is current magnitude, R is circuit resistance. The less noble part of a corrosion cell - negatively charged - dissolves metallic iron then converts it to positively charged ions - generates electrons - where oxidation occurs. - Answer -Anode The more noble region on the electrode - where electrons are consumed - positively charged - where reduction occurs - Answer -Cathode The difference in potentials between the anode and the cathode create what? - Answer -Voltage difference, which is the driving force for corrosion. Allows for electrons generated at the anode to transport to the cathode. - Answer -Return path (metallic pathway) Conducts ionic current - water-based - contains ions - pathway to transport ions - carries corrosion current - Answer -Electrolyte Negatively charged ions - Answer -Anions Positively charged ions - Answer -Cations Four parts to a corrosion cell - Answer -Anode, Cathode, Return Path, Electrolyte Oxygen ____________ the rate of corrosion - Answer -Increases Corrosion proceeds ____________ in warmer environments than in cooler ones - Answer -Faster Chemical Salts like Sodium Chloride, act as a hygroscopic material (draws moisture from the air), which _____________ corrosivity in non immersed areas. - Answer -Increases The wetter the environment, the ____________ corrosion is likely to occur - Answer -more What are the two types of corrosion? - Answer -Localized and General Corrosion that occurs in discrete sites on the metal surface - often occurs in areas difficult to inspect - Answer -LocalizedCorrosion that occurs relatively uniform over the entire surface - Answer -General What type of corrosion can initiate at an open, freely exposed surface or at imperfections in the coating? - Answer -Pitting Corrosion The type of corrosion that occurs on a metal surface that is shielded from full exposure to the environment because of the close proximity of another material: (ex. common on support straps, or pipe flanges) - Answer -Crevice Corrosion The type of corrosion that occurs through the electrochemical action of two dissimilar metals in contact in the presence of an electrolyte and an electron conductive path (Return Path): - Answer -Galvanic Corrosion The less effectively the coating insulates the structure, the __________ electric current is required to provide catholic protection. - Answer -more Two types of Cathothic Protection Systems - Answer -Impressed; Galvanic A device that uses power from electric utility lines to convert the alternating current to a lower voltage direct current by means of a step down transformer - Answer -Rectifier What is the minimum requirement for a cathodic protection potential? - Answer --0.85V What occurs when potential in a cathodic protection system increases (more negative) - Answer - Hydroxyl formation; Cathodic disbondment Note: if the potential continues to increase(more negative) disbondment occurs through the hy