| Résumé : |
For industrial, marine, and offshore facility owners, the cost consequences of corrosion under insulation (CUI) can be intolerable in terms of lost production, chemical spills, environmental cleanup, and health and safety implications. Hence, it is very important to implement carefully designed CUI mitigation strategies.
Specialty coatings can be excellent tools for CUI mitigation strategies. The authors showed in previous laboratory investigations using a CUI cyclic test, that coated carbon steel pipe insulated with Cal-Sil (calcium silicate) saturated with a 1% NaCI (sodium chloride) salt solution performed best with either thermal spray aluminum (ISA) or a spray-applied titanium modified inorganic copolymer (TMIC). The raison d'etre for the use of calcium silicate as an insulation material was because it readily absorbs and wicks moisture and can bold about 20-40 times its weight in water,4 thus representing a worst-case scenario.
The cyclic temperature range used in the earlier work was 95 C to 445 C.2, 3 The temperature span was intended to ensure that the coated pipe test pieces were exposed to the NACE RP01985 critical corrosion temperature range (4 C to 175 C for carbon steel; 50 C to 175 C for stainless steel) and higher. Interestingly, an anomalous finding from the earlier work was that corrosion on wet and insulated bare steel pipe appeared to occur at temperatures higher than those known for the corrosion of dry carbon steel 1.5, 6 This suggested that temperatures, measured by thermocouples on bare steel pipe encased in dry insulation, which were used to indicate temperatures of coated steel pipe encased in wet insulation, were incorrect and needed to be checked to provide greater accuracy. These new temperature measurements were carried out as part of this new CUI study.
The primary aim of the current investigation was to evaluate coating performance on both carbon steel and stainless steel pipes in the temperature range for CUI and at elevated temperatures approaching 600 C. Utilizing the Cyclic Pipe test, the cyclic temperature resistance of a new member of the TMIC class of coatings was compared and contrasted with one of the other specialty coatings studied in the previous work, an inorganic coating containing micaceous iron oxide (hereinafter Coating A and designated Coating #2 in the former study). Both the original TMIC coating tested and the new TMIC coating evaluated in this study were aluminum filled. They were formulated to provide similar flexibility, be unaffected by intra-film stresses during high temperature cycling in the typical CUI temperature range, and withstand cycling and continuous operation between ambient and elevated temperatures. In the present investigation, the new TMIC coating was touted to perform up to 600 C, much greater than the 450 C limit for the earlier version. |
Aller sur edunet
Accueil
Biological aging and the neutral swelling of insoluble collagen in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. LXI (Année 1966)
