Abstract
The cracking and subsequent corrosion in water ballast tanks has long been a problem for the maritime industry. The potential damage to ships’ hulls from this type of corrosion can be devastating and catastrophic. Consequently, there has been much study into the root causes of coatings cracking over the years. These studies have primarily centered on the mechanical considerations of crack initiation and propagation. It has generally been agreed that cracking is due to stress in the film of various causes.
One facet of the cracking problem which has not been studied, to any great degree, is what happens after the crack has formed and corrosion commences. Worth considering is the extent corrosion and cathodic delamination progresses under the film at the crack point. Although corrosion is inevitable at the crack point, limiting its progress can provide valuable savings in the repair of any corrosion damage.
This study will look at the mechanisms of corrosion and cathodic delamination resulting from the cracking of paint in a water ballast tank environment and what may be expected in the corrosive environment. This will be based on the concept of a thermodynamic barrier existing at the coating/steel interface resulting from Lewis acid-base interactions between polymer and substrate. It has not escaped the authors’ notice that these same Lewis acid-base interaction that govern adhesion are also applicable to interaction between the polymer and filler/pigment components of the coating which may provide reinforcement to the coating allowing for improved crack resistance.
