The development of a marine antifouling system using environmentally acceptable and naturally ...

211 Pages·2010·19.2 MB·English

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U S
NIVERSITY OF OUTHAMPTON

FACULTY OF ENGINEERING, SCIENCE & MATHEMATICS
SCHOOL OF ENGINEERING SCIENCES
SURFACE ENGINEERING AND TRIBOLOGY RESEARCH GROUP

THE DEVELOPMENT OF A MARINE ANTIFOULING SYSTEM USING
ENVIRONMENTALLY ACCEPTABLE AND NATURALLY OCCURRING
PRODUCTS

By
Lily D. Chambers

THESIS SUBMITTED FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

Oct 2008
UNIVERSITY OF SOUTHAMPTON
ABSTRACT
FACULTY OF ENGINEERING, SCIENCE & MATHEMATICS, SCHOOL OF ENGINEERING SCIENCES
Doctor of Philosophy
THE DEVELOPMENT OF A MARINE ANTIFOULING SYSTEM USING ENVIRONMENTALLY
ACCEPTABLE AND NATURALLY OCCURRING PRODUCTS
By Lily D. Chambers

Due to legislative pressures and the recent ban of trybutyl tin, alternative environmentally acceptable ship
hull antifouling systems are required. This thesis uses a multidisciplinary approach to combine two disparate
areas of research namely marine biology and surface engineering, to develop a novel natural product (NP)
based antifouling system. The overall objective of this thesis is to transfer a natural marine biological
defence mechanism into an engineered antifouling coating system. By combining natural product extraction
and incorporation into a trial coating an extensive test programme was able to investigate the antifouling
performance and address the issues of bringing this active area of research to the next technological readiness
level. By using a stepwise approach to the development of the engineered solution, a suite of techniques
were used to fully characterise a NP based system. The biological and surface engineering techniques
adapted and developed are described here and their future use to evaluate a novel NP based antifoulant
system is critically assessed.
After an extensive literature review, an ethanol extract from the red seaweed Chondrus crispus was selected
as the natural product source. NP specimens were harvested locally and also purchased as industrially
processed dried algae. The industrially processed algae showed good antifoulant activity ( ≤ 25 µg mL-1) in
laboratory bioassays and had a greater efficacy than the locally harvested samples highlighting its potential as
an economically viable solution. The direct incorporation of the NP into a commercial control depletion
polymer binder, allowed for the rapid development of characterisation techniques to evaluate the effects this
had on the performance of the NP-binder matrix. The feasibility of a range of electrochemical techniques to
measure corrosion potential, impedance, resistance and water uptake in the NP coating was critically
assessed. A combination of open-circuit potential and electrochemical impedance spectroscopy provided a
unique and rapid means to non-destructively measure the contribution of incorporated NPs to the degradation
and water uptake of the binder film. Studies of biofilm growth were used to successfully measure
community viability and structure using fluorescent staining and differential interference contrast
microscopy. These techniques were found to be very informative on Southampton water marine biofilm
community structure and were cross correlated by fourier transform infrared measurements. Resistance to
biofouling was determined through field trials, an important testing platform for an antifouling system, and
specifically trials which test the entire coated system including any primers and substrate preparation
requirements. An initial NP antifouling performance greater than the booster biocide (Chlorothalonil) control
was documented for one field trial over a period of the first 6 weeks.
A key aspect was to determine the potential efficacy of NPs and their viability in a coating system. To
achieve this, a range of standard and non-standard techniques were used to assess this novel combination of
crude NP extract and commercial binder system. This work has shown that a limited antifoulant activity is
achievable. By evaluating the effect of a NP on both the fouling community and a binder system this unique
approach helps define key techniques to assess future NP antifoulants and identifies the optimisation required
to increase their functionality.

ii
Abstract ii
Table of Contents iii
Table of Figures vi
Table of Tables xi
Nomenclature xiii
Author’s Declaration xivi
Acknowledgements xv
1 Introduction 1
1.1 Research motivation 2
1.2 Thesis structure 8
1.3 References 10
2 Literature review 11
2.1 Biofouling 12
2.2 Fouling penalties 15
2.3 Historic antifouling methods 17
2.4 Modern antifouling alternatives 20
2.4.1 Heavy metals 22
2.4.2 Booster biocides approach 23
2.4.3 Foul release approach 24
2.4.4 A biomimetics approach 25
2.4.5 Further antifouling coatings 32
2.5 System requirements 33
2.6 Summary and outlook 34
2.7 References 36
3 Experimental techniques 45
3.1 Introduction 46
3.2 Electrochemical techniques 49
3.2.1 Open-circuit potential (OCP) 50
3.2.2 Zero resistance ammeter (ZRA) 51
3.2.3 Electrochemical impedance spectroscopy (EIS) 51
3.3 Biofouling analysis techniques 54
3.3.1 Biofilm analysis 54
3.3.2 Field exposure trials 55
3.3.3 Environmental parameters 57
3.4 Microscopy & FTIR techniques 58
3.4.1 Fourier transform infra-red (FTIR) microspectroscopy 58
3.4.2 Episcopic differential interference contrast (EDIC) microscopy 58
3.4.3 SEM and EDX 59
3.4.4 Optical microscopy 60
3.4.5 Gas chromatography – mass spectroscopy (GC-MS) 60
3.5 References 62
4 Natural product antifoulant 64
4.1 Natural products 66
4.2 Issues with natural products 67
4.3 Natural product source 67
4.4 Natural product antifoulant 68
4.5 Natural product antifoulant characterisation 69
4.5.1 Extraction 70
4.5.2 Bioassay 70
4.5.2.1 Microfouler bioassay 71
4.5.2.2 Macroalgae bioassay 73
4.5.3 Results 75
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4.6 Discussion 77
4.6.1 Extraction 77
4.6.2 Bioassay 77
4.7 Conclusions 79
4.8 References 81
5 Building the antifouling system 84
5.1 Substrate 86
5.2 Coating 87
5.2.1 Primer 87
5.2.2 Top-coat 88
5.2.3 Positive control coatings 89
5.3 Antifouling additives 89
5.3.1 Natural product extract 89
5.3.2 Control biocide 90
5.4 Application 90
5.5 Material characterisation 91
5.6 References 95
6 Electrochemical characterisation 96
6.1 Electrochemical characterisation 99
6.1.1 Open-circuit potential (OCP) 99
6.1.2 Zero resistance ammetry (ZRA) 100
6.1.3 Electrochemical impedance spectroscopy (EIS) 102
6.1.4 Linear polarisation 103
6.2 Results 104
6.2.1 Substrate preparation affects 104
6.2.2 Coating thickness affects 108
6.2.3 The affect of antifoulant additions to coatings on steel 110
6.3 Discussion 126
6.3.1 Substrate preparation affects 126
6.3.2 Coating thickness affects 126
6.3.3 The affect of antifoulant additions to coatings on steel 128
6.4 Conclusions 134
6.5 References 136
7 Biofouling characterisation 138
7.1 Marine biofilm analysis 140
7.1.1 Biofilm analysis methods 141
7.1.2 Staining technique 143
7.2 Field trials 145
7.2.1 Immobilised natural product field trial 145
7.2.2 Experimental antifouling coatings field trials 146
7.3 Results 151
7.3.1 Microbiological biofilm 151
7.3.2 Field trial immobilised extract 156
7.3.2.1 FTIR results 156
7.3.2.2 EDIC results 156
7.3.3 Field trails 158
7.4 Discussion 166
7.4.1 Laboratory biofilms 166
7.4.2 Field trials biofouling 168
7.5 Conclusions 174
7.6 References 175
176
iv
8 Conclusions and Further Work
8.1 Conclusions 177
8.2 Further work 182
8.2.1 Natural products 185
8.2.2 Delivery mechanism 186
8.2.3 Leaching rates 187
8.3 References 188
Appendix I 189
Appendix II 190
Appendix III 191
Appendix IV 192
Glossary 194

v
List of Figures

Figure Description Page
number

Figure 1.1 Thesis in context of world-wide research areas 6

Figure 1.2 Key interactive parameters affecting an antifouling coating system 7

Figure 1.3 Schematic of antifouling system showing the interactive parameters and the 8
coating layers

Figure 1.4 Key tests to optimise an NP-based antifouling system 10

Figure 2.1 Schematic of critical biofouling stages 12

Figure 2.2 Schematic of the boundary layer development along a ship hull 16

Figure 2.3 Microscope image of biofilm on mild steel 17

Figure 2.4 Timeline for key antifouling generations 18

Figure 2.5 Schematic of (a) soluble matrix biocide releasing coating and (b) insoluble 22
biocide releasing coating with antifoulant loaded and depleted antifoulant

Figure 2.6 Phyletic distribution of 160 reviewed marine species from which potential 26
antifouling natural products have been extracted

Figure 2.7 The effective concentrations (EC) of various natural products to inhibit 50% 27
of the tested population of the barnacle B. amphitrite

Figure 3.1 Schematic cross-section of an antifouling system showing environmental 47
interactions

Figure 3.2 Equivalent circuit of (a) an organic coating on a metal substrate and (b) a 52
coated metal with a defect

Figure 3.3 Theoretical magnitude plots based on the intact and damaged coating 53
equivalent circuits

Figure 3.4 Solent water environmental parameters at 1 m depth 2007 55

Figure 3.5 Field trial testing protocol 57

Figure 3.6 Diagram of the optical light path in an EDIC microscope 59

Figure 3.7 Scanning electron microscope electron gun spot size sampling area 60

Figure 3.8 Experimental testing programme and designated chapters 61

Figure 4.1 Chemical structure of the natural product furanone where R = Br or R=H 66

Figure 4.2 Schematic of a 96-well plate and concentration regime used for bioassays 71

Figure 4.3 Flow chart for the process of 96-well plate treatment with extracts and 74
bioassay, adapted from (Fletcher 1989)

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Figure 4.4 Diagram of inverted individual well illustrating the settlement assay of 75
macroalgae zoospores

Figure 4.5 Extract A germination resistance against (a) Undaria and (b) Ulva spores. 76
Means of n=30 plotted with standard deviation error bars

Figure 4.6 Extract B germination resistance vs. (a) Undaria and (b) Ulva spores. Means 77
of n=30 plotted with standard deviation error bars

Figure 4.7 GC-EIMS - Electron Ionisation mass spectrometry of algal NP 79

Figure 5.1 Average roughness (R ) and total roughness (R) measurements for different 91
a t
steel substrate preparations (n=3)

Figure 5.2 Optical micrographs of the transverse section of blank AF coating system on 92
(a) 600 grit steel surface (b) abrasive grit steel surface and SEM
micrographs of (c) 600 grit steel surface (d) abrasive grit steel surface

Figure 5.3 Average and total roughness of algal NP and blank topcoat surface (n=3) 93

Figure 5.4 Optical micrographs of un-wetted coatings on steel 93

Figure 6.1 Galvanic couple arrangement for ZRA experiments 100

Figure 6.2 Flow chart of the procedure of each experiment for EIS boxed in orange and 101
ZRA boxed in blue

Figure 6.3 Apparatus of three electrode electrochemical cell with 7 cm2 working area 102
for EIS and OCP laboratory experiments

Figure 6.4 OCP of varying steel surface preparation methods of mill scale, as well as 104
600 and 1200 SiC wet/dry polish

Figure 6.5 Characterisation of steel in 3.5 % NaCl solution at 0.5,1,1.5 and 2 h using 106
(a) open-circuit potential and (b) electrochemical impedance spectroscopy as
a Bode plot

Figure 6.6 A twenty-four hour characterisation of steel in 3.5 % NaCl solution using (a) 108
open-circuit potential and (b) electrochemical impedance spectroscopy as a
Bode plot

Figure 6.7 OCP for blank topcoat with increase in thickness after 10 minute 109
immersions in 3.5 % NaCl

Figure 6.8 Impedance at 1 Hz for varying coating thickness in 3.5 % NaCl after 2 hrs 110
vs. Ag/AgCl

Figure 6.9 OCP of coupled 12 ± 2 µm coatings in seawater (all in same beaker) 111

Figure 6.10 OCP of coupled 15 µm dft coatings in seawater (all in separate beakers) 111

Figure 6.11 ZRA mixed potentials and decoupled potentials of (a) Blank topcoat (12 ± 2 112
dft) (b) Biocide (15 ± 2 dft) and (c) Algal NP extract (13 ± 2 dft) topcoats
coupled to uncoated steel

Figure 6.12 Top-coat (30 µm) of blank, biocide and algal NP OCPs in 3.5 % NaCl over 113
two weeks (day mean with standard deviation error bars)
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Figure 6.13 Blank topcoat, Algal NP topcoat, Biocide topcoat (30 µm dft) OCPs in 3.5 114
% NaCl over five days

Figure 6.14 EIS Bode plot for 30 µm blank topcoat in 3.5 % NaCl for two weeks 115

Figure 6.15 EIS Bode plot for 30 µm algal NP topcoat in 3.5 % NaCl for two weeks 116

Figure 6.16 EIS Bode plot for 30 µm biocide topcoat in 3.5 % NaCl for two weeks 117

Figure 6.17 100 day aged top-coat (30 µm) OCPs in 3.5 % NaCl over two weeks 118

Figure 6.18 OCP of 80 µm thick coatings with primer in seawater at laboratory (nutrient 119
limiting)

Figure 6.19 Dry film thickness increase of the 80 µm coating system after immersion in 119
aerated seawater in laboratory for 60 days on either side of the coated
sample

Figure 6.20 Before and after images of the coated samples (50 x 50 mm) immersed for 120
60 days in aerated seawater in laboratory

Figure 6.21 OCP of 100 µm thick coatings with primer in Solent seawater summer field 121
trial (nutrient rich)

Figure 6.22 Bode plots of the samples in 3.5 % NaCl, 18 ºC ± 2 after 105 days in field 122
trial

Figure 6.23 Images of the field trial samples of the online OCP data set at 42 days and 124
on removal at 105 days (Nov 2007)

Figure 6.24 Proposed equivalent circuit for an antifouling coating on steel 125

Figure 6.25 Exposed surface of blank topcoat in a blank to blank topcoat couple 127
measured using ZRA in laboratory aerated seawater for 5 days

Figure 6.26 SEM micrograph of blank topcoat after 5 day ZRA experiment, with optical 127
microscope images of the exposed (top) and unexposed (bottom) and
element percentages from EDX spot analysis in yellow

Figure 6.27 (a) OCP data and (b) water uptake measurements for 30 µm dft blank and 131
algal coating on steel in 3.5 % NaCl solution

Figure 6.28 Schematic of pathway (1) through pores and voids and (2) through the 132
controlled depletion layer

Figure 6.28 Decoupled OCP measurements of 12 µm dft in aerated seawater 136

Figure 7.1 Plan view of experimental immersion set up (trial 1) of the biofilm viability 141
experiment on 1% algal NP topcoat, blank topcoat and uncoated glass slides

Figure 7.2 Plan view of experimental immersion set up (trial 2) of the biofilm viability 142
experiment on 1, 5 and 10 % algal NP and blank topcoat

Figure 7.3 Glass slide immersion positions for laboratory trial 1 (a) parallel to the base, 142
viii
and trial 2 (b) at an angle to the base of the beaker in aerated seawater

Figure 7.4 Live/dead bacteria staining protocol 144

Figure 7.5 Immersion board for the immobilised natural product field trial 146

Figure 7.6 Biofilm staining of steel after 1 week immersion in aerated seawater in the 151
laboratory at room temperature (≈ 18 ºC)

Figure 7.7 Marine biofilm after 3 weeks of glass slide in laboratory trial 2 151

Figure 7.8 Live/dead bacterial viability in laboratory aerated seawater (nutrient limited 152
environment) for comparison of Blank topcoat (a) and 1 % Algae (b) on
glass slides

Figure 7.9 Environmental parameters of immersion tanks for laboratory aerated 153
seawater sampled 26th April 2006 for comparison of 1 % Algae and Blank
topcoat on glass slides

Figure 7.10 Figure 7.10 Individual (a) temperature (b) dissolved oxygen (c) pH and (d) 154
conductivity data for 1 %, 5 %, 10%, blank and control seawater in beakers

Figure 7.11 Live bacterial percentage coverage on 1, 5 and 10 % algal NP topcoat, glass 155
slide and blank topcoat

Figure 7.12 FTIR baseline corrected spectra of 25 µg mL-1 (red), 50 µg mL-1(green), 156
1100 µg mL-1 (purple) algal NP chemically immobilised on glass slides and
immersed in seawater for 1 week

Figure 7.13 Live (a) and dead (b) viability of seawater biofilm on 25, 50 and 1100 µg 157
mL-1 algal NP immobilised onto glass slides, error bars are standard
deviation

Figure 7.14 Images of the marine biofouling on 25, 50 and 1100 µg mL-1 algal extract 158
concentrations

Figure 7.15 Field trial 1 environmental parameters May – Aug 2006, Empress Dock, 159
Southampton

Figure 7.16 Field trial 2 and 3, environmental parameters Feb – Nov 2007, Empress 159
Dock, Southampton

Figure 7.17 Field trial 1 after 2.5 months immersion (June 2006) 160

Figure 7.18 End of field trial 1 after 4 months immersion (August 2006) 160

Figure 7.19 Field trial 2 after 2.5 months immersion (June 2007) 161

Figure 7.20 End of field trial 2 after 6 months immersion (September 2007) 161

Figure 7.21 Field trial 3 after 1.5 months immersion (September 2007) 162

Figure 7.22 End of field trial 3 after 3 months immersion (November 2007) 162

Figure 7.23 Field trial 1 ranking of biofouling growth with respect to time, 2007 163
Empress Dock, Southampton
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