Coating performance and longevity is highly dependent on the quality of substrate surface preparation. The effect of profile height, profile type (e.g., type of tool used to perform the prep, angularity of profile, etc.), extent of cleanliness, and amount of chloride contamination on coating performance were all studied to determine the correlation between these factors in an attempt to identify the primary factor in coating failure due to improper surface preparation.

This paper describes experimental work investigating the influence of steel surface roughness on the adhesion performance of fusion bonded epoxy (FBE) pipeline coatings. The paper begins with a summary of the standards and methods that can be used to measure surface roughness. Several parameters are used to characterize the roughness of a blast cleaned steel including profile peak height and peak count. Tortuosity and rugosity indicate the proportional increase in steel surface area developed by roughening the surface. Normal pipeline coating industry practice is to specify and control a single roughness parameter termed “surface profile”. It is measured with replica tape and corresponds to the maximum peak-to-valley height.In the experimental work steel panels were abrasive blast cleaned with various steel shot and grit abrasives and the roughness characteristics of the blast cleaned surface were measured with stylus profilometers conventional replica tape and 3D imaging of replica tape.A FBE pipeline coating was applied to the prepared steel panels. The adhesion performance of the FBE coating was evaluated using the following test methods.<ul><li>Hot water immersion adhesion rating per CSA Z245.20 section 12.14 </li><li>Pull-off adhesion strength after hot water soak exposure per ASTM 4541 </li><li>Cathodic disbondment radius at 65 and 80 °C per CSA Z245.20 section 12.8 </li><li>Time before blisters were observed in Atlas Cell per NACE TM0174 modified </li><li>Average blister diameter in Atlas Cell </li><li>Pull-off adhesion strength after Atlas Cell exposure per ASTM 4541 </li></ul>The experimental data were analyzed using statistical techniques to investigate the relationship between the measured surface roughness and the adhesion test results. The adhesion results were found to be positively and linearly correlated with substrate tortuosity and rugosity. Profile peak height and peak count were found to contribute to tortuosity.

Coating application on the exterior of ocean-going vessels and offshore platforms is normally very time sensitive, and frequently must be performed during times of high humidity, sweating hulls and daily rain showers. This paper will describe the use of solvent free, surface tolerant epoxies that can be applied to wet surfaces during times of very high relative humidity. Both the positive and negative aspects will be covered.