Estimation of anti-fouling paint thickness and its use in extending the lifetime of a ship's underwater hull coating system

Abstract

The underwater hull paint system on an aircraft carrier is comprised of anti-corrosive (AC) and anti-fouling (AF) paint. The AF paint is designed to continuously ablate during the ship's operational cycle, releasing toxins that inhibit marine growth on the hull's surface. In 1997, Whitaker, Wimmer, and Bohlander performed a least squares regression to develop a model that predicts the total coating system wear using dry film thickness (DFT) measurements taken in drydock. The model is derived without use of data taken by remotely operated vehicles (ROV), which measure paint thickness underwater with the potential for variations due to paint swell. An analysis of data taken by ROV is performed here with an attempt made to modify the existing model to include its use. Also, the model has no mechanism to account for the application of additional layers of AF paint at an interim drydock, making it unreasonable to use the model to predict the distribution of paint thickness following two operational cycles with an interim painting. To allow for this prediction, an estimate for the mean thickness of one coat of AF paint is determined. Using this determined estimate and the mean of the predicted distribution for the interim drydock, a simple method is derived for estimating the mean thickness of a hull's total coating system following two operational cycles. This method provides enough information to facilitate deciding in advance how many coats of AF paint to apply at that interim drydock to ensure hull integrity is maintained until the second drydocking evolution.