Corrosion Technician Exam Questions And Answers. Updated

Corrosion Technician Exam Questions And Answers. Updated __________________________ is a method which interferes with the flow of the current in the electrochemical cell - ANSWER -cathodic protection ________________ can be used in underground or emersion situations. - ANSWER -cathodic protection _________________________________ are low-alloy steels formulated specifically to form tightly adherent, dense corrosion products that inhibit corrosion in some atmospheric environments. - ANSWER -weathering steels _______________________, unlike general corrosion, occurs at discrete sites on a metal surface. - ANSWER -localized corrosion _____________________ is a deep, narrow corrosive attack which often cause rapid penetration of the substrate thickness. - ANSWER -pitting _________________________ is characterized by corrosive attack in a localized region surrounded by corrosion free surfaces, or surfaces that are attacked to a much lesser extent. - ANSWER -pitting corrosion Very often, a local cell is set up between the interior of the pit and the external surface. The interior contains ______________________ that are quite corrosive compared with the bulk of the solution. - ANSWER -acidic, hydrolyzed salts An __________ is established within the pit, and the surrounding surfaces act as cathodes. - ANSWER -anode True or false? Pits develop at weak spots in the surface film and at sites where the film is damaged mechanically under conditions where self repair will not occur. - ANSWER -True The importance of pitting depends on the thickness of the metal, thus on ____ sections pitting may be serious, while on _______ pitting is of less importance. - ANSWER -thin, thick List the four stages of pitting. - ANSWER -1. initiation 2. propagation 3. termination 4. reinitiation True or false? Pits develop at weak spots in the surface film and at sites where self repair will occur. - ANSWER -False: Pits develop at weak spots in the surface film and at sites where self repair will NOT occur. In general the rate of penetration ______________ if the number of pits increase. - ANSWER -decreases Movement of the solution over the metal surface often ______________ and may even _______________ pitting that otherwise would occur if the liquid were stagnant (such as with austenitic stainless steels in seawater). - ANSWER reduces, prevent During the initiation step of pitting, where does pit initiation occur? - ANSWER at defects or imperfections in a protective or passive film Defects that cause pit initiation may be _____________________ or are caused by________________. - ANSWER -randomly distributed, mechanial damage to the films Pitting may not initiate for long periods, but once it does it can - ANSWER propagate rapidly In the propagation step, corrosion is driven by - ANSWER -the potential difference between the anodic area inside the pit and the surrounding cathodic area A pit may terminate because of.... - ANSWER -increased internal resistance of the local cell caused by filling with corrosion products, filming of the cathode, etc. Sometime pits are reinitiated when they are ___________ - ANSWER -Rewetted due to re-establishment of the conditions or to the differential aeration between the solution in the main pit cavity and solutions in some of the cracks that emanate from deeper in the metal. True or False? In structural members where strength alone is a concern, pitting alone may not be as important as in a service of containing fluid. - ANSWER True What does PREN stand for? - ANSWER -Pitting Resistance Equivalent Number _________________ removes material from the surface until no further pits are evident. - ANSWER -routing __________________ is the most accurate method for measuring pits. - ANSWER -Routing What variation of the routing method can be used to measure the maximum pit depth on the outside of the pipe? - ANSWER -Placing a sample length in a lathe and machine it until no further corrosion is evident What is pitting frequency? - ANSWER -the number of pits per unit area Why is pitting corrosion more difficult to define than general corrosion? - ANSWER -Because the exact location of the pits cannot be predicted. The introduction of small amount of ions, of metals such as _______________, _______________, and _______________ may cause severe corrosion of aluminum equipment. - ANSWER -copper, lead, mercury Corrosion of upstream copper alloy can cause ... - ANSWER -contamination of cooling water __________ _______________ has been used effectively to control pitting on body exposed surfaces. - ANSWER -Cathodic Protection ___________ _______________ is not recommend where pitting may occur. - ANSWER -Anodic Protection __________________ ___________ is a form of localized attack in which the size of the attack is an area where free access to the surrounding environment is restricted. - ANSWER -Crevice corrosion