Session: 02-05-01 Reliability of Marine Structures

Paper Number: 87377

87377 - Degradation and Testing of Marine Heavy Duty Protective Coatings 

Steel constructions are protected from the corrosive marine atmosphere by heavy duty paint coatings, typically based on epoxy binders. This paper presents a statistical analysis of root cause for coating failure on offshore installations, and a correlation study between accelerated lab tests and a field test. The results showed that the dominating initiation mechanism is low film thickness over edges and welds. Liquids tend to retract from sharp edges due to their surface tension. Rounding of edges and stripe coating is supposed to mitigate this, but evidently this is not entirely successful. Subsequent expansion of the damaged area by corrosion creep was found to be small. Coatings with zinc rich primers showed very little creep around the initial damage. Hence, coating lifetime and decisions about coating maintenance will then depend more on corrosion depth and less on degraded area. The most used accelerated coating test methods are discussed with respect to correlation to field performance and relevance with respect observed coating failure mechanisms. The test methods focus on corrosion creep around damages, which both field testing and statistical analysis of field data show are not important to coating lifetime. Given that coating failures were mainly found at edges and welds, it is reasonable to assume that the degradation was caused by barrier failure due to low film thickness. This property is rarely investigated or tested in coating selection programs.

Presenting Author: Ole Knudsen SINTEF

Authors:

Ole Knudsen SINTEF
Catalina Hagen SINTEF
Anders w.b. Skilbred Jotun
Andreas Løken Jotun
Daniel Höche Helmholtz-Zentrum Hereon
Bahman Daneshian Helmholtz-Zentrum Hereon