1. Delamination of Coating from a Ship’s Hull
Robert B Leggat, phD
JPCL Webinar 18 July 2018

2. Aircraft Carrier in Dry Dock
Freeboard
Deep Load Line (DLL)
Boot Top
Light Load Line (LLL)
Underwater
Hull
U.S. Navy photo by Mass Communication Specialist 1st Class Joshua J. Wahl

3. Coating Application Sequence

4. Field Investigation
U.S. Navy photo by Photographer's Mate 2nd Class Steven King

5. Coating Peeling on Boot Top
Starboard side facing aft
Portside facing aft

6. Coating Peeling on Freeboard
Portside- grey polysiloxane peeling in band within 1 ½ feet of DLL

7. Sampling Locations All samples mechanically chipped to bare metal and
Upper:
Intact Coating
in Freeboard
All samples mechanically
chipped to bare metal and
showed cohesive failure within
red anti-corrosion primer
Middle:
Peeling Coating
in Freeboard
Near DLL
Lower:
Peeling Coating
in Boot Top

8. Laboratory Investigation
1. Why did the gray polysiloxane
coating disbond in the freeboard
just above the DLL?
2. Why did the anti-fouling coating
disbond from the anti-corrosion in
the boot top?

9. Paint Chips from Freeboard
Upper location:
Grey polysiloxane /
Grey anticorrosion /
Red anticorrosion
Middle location:
Grey polysiloxane /
Red antifouling
Grey anticorrosion /
Red anticorrosion
10 mils

10. Paint Chips from Boot Top
Solvent rub test confirmed
that disbonding occurred
between red anti-fouling
and gray anticorrosion layers
Black Antifouling
Coating
10 mils
Red Antifouling
Coating

11. Catalytic Reaction with Copper
Mix Ratio Analysis
Nitrogen Analysis of Gray Anticorrosion Layer
Oxidation
In Furnace
Catalytic Reaction with Copper
NOx
Detection
by IR N2
Hardener component of the gray anticorrosion coating
contained polyamide and polyamidoamine
Compared to properly mixed 1:1 control sample, 2 out of 7
gray anticorrosion coating chips had a proper mix ration of 1:1,
while 5 out of 7 had excess nitrogen with mix ratios ranging
from 1.05 : 1 to 2 : 1.

12. Mix Ratio Analysis FTIR Analysis of Gray Anticorrosion Layer
Band Intensity Comparison
1506 cm-1 (epoxy) vs
1454 cm-1 (hardener).
Confirmed results of
Nitrogen Analysis
Indicating excess hardener
in gray anticorrosion coating

13. Recoat Interval Study
2 Hours
4 Hours 40 Minutes
6 Hours
8+ Hours
Adhesion markedly better for recoat window between
gray anticorrosion coating of 2 hour vs longer times

14. Tack Time Test Ratio of A to B Substrate
Time from AC Application until No Longer Wet
Time from AC Application until No Longer Tacky
1 : 1
Steel Panel-
Same as Recoat Study
1 hour and 45 minutes
4 hours and
15 minutes
1.4 : 1
2 hours
3 hours
Glass Panel -
6 mil WFT Drawdown
1 hour and
45 minutes
1.05 : 1
4 hours
1.1 : 1
30 minutes

15. Conclusions
Disbonding above the deep load line (DLL) was caused by application of the polysiloxane over the antifoulant coating (AF), instead of the anti-corrosion coating (AC).
There was off-ratio mixing of the gray epoxy AC in some cases.
Spontaneous disbonding and poor adhesion of the AF below the DLL resulted from exceeding the tack time of the AC which was aggravated by the off-ratio mixing

16. Recommendations
The shipyard and coating contractor should review QA/QC records to determine in which areas tack time was likely to have been exceeded.
The coating should be removed in the areas where peeling is observed or have been identified as being susceptible.
Coating should be removed by hand or mechanical tool cleaning and/or high pressure/ ultrahigh pressure water blast cleaning.