API RP 571 3.8 Atmospheric Corrosion Final Exam Version 1 Questions And Accurate Answers.

3.8.1 Description of Damage - correct answers Corrosion that occurs from moisture associated with atmospheric conditions. Marine environments and moist, polluted industrial environments with airborne contaminants are the most severe. Dry rural environments cause very little corrosion. 3.8.2 Affected Materials - correct answers Carbon steel, low-alloy steels, and copper alloyed aluminum. 3.8.3 Critical Factors - correct answers a) The physical location of the plant (industrial, marine, urban, rural). b) The amount of moisture (humidity, rainfall) typically present or the presence of cooling tower mist. c) The presence of salts, sulfur compounds, dirt, or other contaminants in the air. d) Chlorides, H2S, fly ash, and other airborne contaminants from cooling tower and wet gas scrubber drift, furnace stacks, and other equipment accelerate corrosion. e) Orientation to the prevailing wind and rain. f) Corrosion rates increase with temperature up to about 250°F (120°C). Above 250°F (120°C), surfaces are usually too dry for corrosion to occur except under insulation. (See 3.22) g) Designs that trap water or moisture in crevices or other configurations are more prone to attack. h) Marine environments can be very corrosive (about 20 mpy) as are industrial environments that contain acids or sulfur compounds that can form acids (about 5mpy to 10mpy). i) Inland locations exposed to a moderate amount of precipitation or humidity are considered moderately corrosive environments (about 1mpy to 3mpy). j) Dry rural environments usually have verylow corrosion rates (1mpy). k) Bird droppings can also cause accelerated corrosion and unsightly stains. 3.8.4 Affected Units or Equipment - correct answers a) Unpainted, uninsulated carbon steel and low-alloy steel piping and equipment operating below 250°F (120°C) where moisture can contact the surface. b) Uninsulated carbon and low-alloy steel equipment with deteriorated paint/coating. c) Equipment downwind of cooling towers and wet gas scrubbers. d) Equipment may be susceptible if cycled between ambient and higher or lower operating temperatures. e) Equipment shut down or idled for prolonged periods unless properly mothballed. f) Tanks and piping are particularly susceptible. Piping that rests on pipe supports is very prone to attack due to water entrapment between the pipe and the support. g) Piers and docks are very prone to attack from the marine environment. h) Bimetallic connections such as copper to aluminum electrical connections. 3.8.5 Appearance or Morphology of Damage - correct answers a) The attack will be general or localized, depending upon the condition of the coating, if any, and whether or not the moisture is trapped. b) If there is no coating, corrosion or loss in thickness can be more general and widespread. c) Localized coating failures will promote localized corrosion. d) Metal loss may not be visually evident, although normally a distinctive iron oxide (red rust) scale forms as shown in Figure 3-8-1. 3.8.6 Prevention/Mitigation - correct answers Paints or coatings are normally applied to otherwise unprotected equipment to prevent atmospheric corrosion. Surface preparation and proper coating application are critical for long-term protection in corrosive environments. 3.8.7 Inspection and Monitoring - correct answers a) VT includes direct/ling-of-sight and indirect methods using a camera, mirror, laser scanning, and/or structured white light imaging with pit gages. b) UT can include techniques like straight beam or angle beam (SWUT or PAUT) to directly measure remaining wall thickness or screening techniques using EMAT or GWT. c) RT may include traditional (film based), digital, or computed radiography media and may incorporate techniques such as contact or profile RT as well as open system imaging. d) ECT may include a screening technique such as pulsed eddy current (PEC). 3.8.8 Related Mechanisms - correct answers Corrosion under insulation (CUI) (3.22) and concentration cell (touch point) corrosion (3.19)