API 571 Damage Mechanisms (as per API 570) Study Guide Review Questions And Answers Well Defined

Highest corrosion rate for atmospheric corrosion? - correct answers Marine and industrial, 20 mpy Up to what temp does atmospheric corrosion increase? - correct answers 250F How to inspect for atmospheric corrosion? (Three) - correct answers VT, UT thickness, profile RT What materials does atmospheric corrosion affect? (Three) - correct answers Low alloy, carbon steel, Cu alloyed Al What materials does boiler water and steam condensate affect? (Two) - correct answers Low alloy, carbon steel What does BWSC corrosion stem from? - correct answers CO2 and O2 (pitting) corrosion What can increase resistance to BWSC corrosion? (Three elements) - correct answers Cr, Cu, Mo In BWSC corrosion, flow assisted corrosion is affected by which temp and pH - correct answers 300F, low pH What NDE used in BWSC? (Two) - correct answers UT and RT to monitor wall thickness What materials does caustic corrosion affect? - correct answers 300 SS, 400 SS How does caustic corrosion come about? - correct answers Caustic added to BFW to neutralize acids, or remove S or Cl- What does caustic corrosion look like? (general + temp, local) - correct answers General thinning at high temps (above 175F) and localized corrosion as gouging How to prevent caustic corrosion? - correct answers Material selection What materials are affected by CUI? - correct answers Low alloy steel, carbon steel, all SS What materials are affected by erosion and erosion/corrosion? - correct answers All What happens in erosion/corrosion when wall thickness is reduced? - correct answers Smaller ID, increased flow velocity, more corrosion What happens in erosion/corrosion when pH is increased and temperature decreases? - correct answers More corrosion How to detect galvanic corrosion? (Three) - correct answers VT and UT thickness gauge, permanent monitors What materials are affected by hydrochloric acid corrosion? - correct answers All How does hydrochloric acid corrosion present? - correct answers Localized and general corrosion What pH causes excessive corrosion of low alloy and carbon steels in hydrochloric acid corrosion? - correct answers 4.5 What kind of attack does hydrochloric acid corrosion do to 300 and 400 SS? - correct answers Pitting How to mitigate hydrochloric acid corrosion? (which material upgrades, three) - correct answers Alloy 400, Ti, Ni NDE for hydrochloric acid corrosion? (Three) - correct answers VT for orange scale, UT/RT for thinning, corrosion probes What is soil corrosion controlled by? (Seven) - correct answers Moisture, temp, resistivity, drainage, cathodic protection, stray current, coating type What are the main factors in soil corrosion? (Three) - correct answers Moisture, dissolved salts, acidity How does soil corrosion present? (Two) - correct answers Deep external thinning and localized pitting How to detect soil corrosion? (Four) - correct answers Above ground VT, pigging, GWT, holiday survey How does sour water corrosion present? (generally, in 300 SS, and under sulfide deposits? - correct answers General thinning, pitting/crevice corrosion/Cl-SCC, pitting What causes sour water corrosion? (corrodents (three), pH) - correct answers H2S/CO2/organic acids, 4.5 to 7 What three factors increase sour water corrosion? (Five) - correct answers H2S concentration, oxygen concentration, pH, temp, velocity How to prevent sour water corrosion? (Two) - correct answers Keep 300 SS under 140F where Cl-SCC not likely Keep pH above 4.5 so that protective scale forms How to detect sour water corrosion? (Two) - correct answers UT scanning and RT for local thinning What materials affected by amine stress corrosion cracking? - correct answers Low alloy and carbon steels What is amine stress corrosion cracking a form of? - correct answers Alkaline SCC What are the factors in amine stress corrosion cracking? (Two) - correct answers Tensile stress and exposure to alkanolamine solution used to remove H2S and/or CO2 What increases amine stress corrosion cracking? (Two) - correct answers Stress and temperature How to mitigate amine stress corrosion cracking? (Three) - correct answers PWHT at and above 635F Use solid or clad SS, other alloys Water wash non PWHT metal prior to welding NDE for amine stress corrosion cracking? (Four) - correct answers WFMT, ACFM, ECT to detect cracking at surface SWUT and PAUT to detect subsurface cracks PT and RT for fine cracks AET to monitor crack growth What materials are affected by caustic stress corrosion cracking? (Three) - correct answers Low alloy, carbon steel, 300 SS What materials can resist caustic stress corrosion cracking? (Two) - correct answers Duplex SS, Ni alloys What causes caustic stress corrosion cracking? - correct answers Caustics (i.e., NaOH) at elevated temps and stress How does caustic stress corrosion cracking present? - correct answers Spider web of small cracks How to mitigate caustic stress corrosion cracking? - correct answers PWHT NDE for caustic stress corrosion cracking? - correct answers WFMT, ACFM, ECT to detect cracking at surface SWUT and PAUT to detect subsurface cracks PT and RT for fine cracks AET to monitor crack growth What materials affected by chloride stress corrosion cracking? - correct answers 300 SS (worst for 8 - 12 % Ni) and some Ni alloys What material is more resistant to chloride stress corrosion cracking? - correct answers Duplex SS How does chloride stress corrosion cracking present? - correct answers Surface initiated spider web like cracking Above what temp does chloride stress corrosion cracking usually occur? - correct answers 140F What are the major factors in chloride stress corrosion cracking? (Five) - correct answers Cl-, increased stress, increased temp, increased O2, low pH How to mitigate chloride stress corrosion cracking? (Three) - correct answers Use Ni alloys above 35 to 45% Use low Cl- water in hydrotest and dry out vessel How to detect chloride stress corrosion cracking? - correct answers Pt and ECT for surface breaking cracks SWUT and PAUT for subsurface cracks