The problems of early coating failure, mechanical damages, and the subsequent corrosion at and around edge areas, are a major concern of the ship’s ballast tank. These problems result directly from: exposure to very corrosive conditions, the deficient edge retention caused by surface tension, surface tension gradient, gravity-driven gradients, and coating’s shrinkage during application and the curing. During recent years, there has been an industrial trend towards the development of edge retention ability such as, using high solid or solvent-free coating materials and applying stripe coatings to protect against the corrosion of ballast tanks. Among these methods, stripe coating is particularly promising because of its various unique advantages over other methods, such as ease of work conditions, sufficient film build, and decrease of substrate irregularities after application of the primer. Relative technical literature and Specifications note that stripe coating is advantageous in preventing coating breakdown on edges, etc., and is often considered the most cost effective measure in heavy corrosive environments. Therefore, stripe coatings are often specified for a project to reduce hull structural failure and enhance the performance of coating system.

According to several reports from tank inspection, it is quite common to measure 500 μm DFT of paint or more on a surface, near edges where a typical two-coat system of 300 μm DFT was specified with two layer stripe coatings. In this study, therefore, edge retention properties were investigated according to coating systems (considering stripe coatings-high DFT and multiple-pass), solid contents and edge grinding conditions (sharp edge, 1C, 2C, 2R, 3R). Furthermore, numerical analysis (CFD, Computational Fluid Dynamics) was carried out with the goal of understanding the effect, if any, in terms of the geometrical discontinuity of steel members in ship’s ballast tanks, on the possibility of coating thickness loss generated by fluid movements during ship’s operation.

Subject
Ballast, Stripe coats, Sharp edges, Water, Coatings, Grinding, Coating thickness, Mechanical failure, Dry film thickness, Coating defects, Epoxies, Paints, Coating systems
Keywords:
edge retention, stripe coating, surface tension, computational fluid dynamics
© 2005 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2005
Association for Materials Protection and Performance (AMPP)
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