Abstract
This is a joint industry study conducted for 18 suppliers and end-users. The study examined the performance characteristics of thirty-one (31) Tank Lining systems, which included Epoxy (Standard, Phenolic and Novolac) and Vinyl Ester coatings, all applied under the same conditions. Tests focused on performance under immersion conditions and included Soak Adhesion, Cathodic Disbondment, Standard Atlas Cell, Pressurized Atlas Cell, and Autoclave. The different tests were used to examine the effects of temperature, pressure, thermal gradient, cathodic protection, acid gases and different liquid types. The initial phase of the test program used 60ºC for all tests and coatings recommended for higher temperature were examined in further tests at 85°C to 125°C. Electrochemical Impedance Spectroscopy (EIS) was also used to examine the barrier characteristics of the coatings and the feasibility of using this non-destructive test to identify degradation of the coatings.
Detailed analysis of results includes examination of variation between coating types and variations between each coating. In these categories both correlation and variations were observed. Five (5) of the thirty-one (31) coatings had good or better performance in all tests conducted at 60°C including three (3) vinyl esters and two (2) novolac epoxy coatings. Five (5) other coatings performed well in at least three (3) of the four (4) tests conducted at this temperature. There were fewer coatings that performed well at higher temperatures, indicating the need for more care in selecting coatings for use in environments that will see temperatures above 60°C. At all temperatures thermal gradient across the coating (the cold wall effect) was noted to be the most likely to result in coating degradation, especially blistering and/or adhesion loss.
