Failure Analysis of Novolac Epoxy Lining System over Amine-Cured Epoxy Primer in Primary Clarifier Launder Trough

Abstract The covered launder troughs in three (3) primary clarifiers were lined to prevent biogenic sulfide corrosion in 2019-2021. In one of the three (3) clarifier troughs, widespread delamination of the lining system occurred within one year of service. The lining remained well-adhered in the other two (2) clarifier troughs. Various parties blamed this failure on different reasons. This inconsistency led to an independent failure analysis investigation. That investigation included review of the inspection reports and weather and site conditions when the lining work was performed. In addition, samples of the disbonded lining were analyzed in the laboratory using microscopy and FT-IR. The field investigation revealed distinct inter-coat delamination of the Novolac epoxy, surfacer, and surface crack filler from the concrete primer/sealer. The field investigation included assessment of the recoat timeframes during construction as well as testing for the presence of amine blush formation. This paper presents the problem, demonstrates the extent of the failure, and clearly shows the lining failure was the result of amine blush formation due to application during condensing conditions in the contained work area.