Use of seawater to improve the static strength and fatigue life of bonded coated steel joints

Abstract

Shipbuilding industry is demanding adhesive solutions for joining components to painted substrates, as traditional welding technologies require costly and time consuming processing operations. However, this topic is rarely considered in the literature. The aim of the current study is to investigate the influence of sodium chloride solution on the static strength and fatigue performance of adhesively bonded painted steel joints. To achieve this, a brittle two component epoxy adhesive was used to manufacture single lap adhesively bonded painted steels. Static and fatigue tests were performed after ageing the joints by immersion in chloride solutions for different periods of time. The results surprisingly show that both the static and fatigue mechanical properties of the joints increase significantly with ageing during the first month of the exposure. The water diffusion taking place for the first month at the single lap joints improved more than 30% both the static and fatigue strength of joints manufactured with this relatively rigid adhesive. The water absorption rate of the adhesive was also calculated using Fick's law relations. The results were used to numerically simulate the humidity level within the adhesive layer in bonded joints.