Abstract
Corrosion protection of ballast water tanks is very precarious because of the aggressiveness of the environment and the difficult accessibility of the areas. Numerous accidents have led to regulation by the International Maritime Organization (IMO). Practical circumstances in yards are often not ideal; therefore it is of interest to investigate if the limits for the parameters, which determine the coating performance, as fixed by IMO are necessary and realistic.
The objective of this study was to verify these limits, in particular concerning the presence of shop primer and presence of (in) soluble salts and dust on the shop primer.
To simulate the possible circumstances in ballast water tanks different exposure methods have been used: exposure of coated samples to seawater at room temperature, cyclic exposure by immersion, drying and temperature change. During exposure (up to four weeks) open circuit potential and impedance measurements were performed. Moreover current was measured during anodic and cathodic polarization of samples with a holiday; this is to assess respectively the corrosion propagation and the susceptibility to cathodic delamination.
Results show that presence of intact shop primer and insoluble salts are beneficial; limits for soluble salt and dust as determined by the regulations are realistic.
