Frosio course hand-out: Section 08 Paints and coatings

Paint technology

Frosio 08 Paints and coatings slide # 1

Paint consists of:

Liquid: Vehicle / Varnish
Binders
Thinners (solvents)
Dry: Powders / Pigments
Colour pigments
Active / Reactive pigments
Extenders
Barrier pigments
Chemicals: Additives
Production enhancers
Storage facilitators
Application aids
Appearance improvers
Service life strengtheners

FROSIO grouping: Binder, Pigments, Extenders, Solvents, Additives

Frosio 08 Paints and coatings slide # 2

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Frosio course hand-out: Section 08 Paints and coatings

Composition of paints
Paints
Binder Pigments Extenders Solvents Additives
Natural Resin Colouring Fillers Hydro carbons Wetting agent
Drying oil
Coal Tar Inhibitive pigm. Stress reducing Ketones Anti-settling
Nitrocellulose
Esters Drier
Synthetic Resin Cathodically
Alkyd protective Ethers Anti-skinner
CR
Epoxy Biocides Alcohols Plasticiser
Polyester
Polyurethane Water
Silicate
Vinyl
Polysiloxane

Frosio 08 Paints and coatings slide # 3

Binders

Frosio 08 Paints and coatings slide # 4

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Frosio course hand-out: Section 08 Paints and coatings

The properties of a paint will be

decided by the binder

Describes the type of

paint/coating
Bind pigments and
extenders to a solid film
Provides the adhesion to the substrate
and cohesion, flexibility in the film
Provides the water, chemical, solvent
and UV resistance

Frosio 08 Paints and coatings slide # 5

Types of binders:
Synthetic resin:
Alkyd
CR
Acrylic Natural resin:
Epoxy Drying oil
Polyurethane Wood rosin
Vinyl Coal Tar
Silicate Bitumen
Polyester Nitro-cellulose

Frosio 08 Paints and coatings slide # 6

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Frosio course hand-out: Section 08 Paints and coatings

Modified binders
A modified paint may
contain more than one
binder, e.g.:
Coal Tar Epoxy
Vinyl Tar
Epoxy Mastic

A binder may be modified

chemically by attaching
new groups to their
molecules, e.g.:
Styrenated Alkyd
Polyurethane-oil Alkyd
Epoxy Ester

Frosio 08 Paints and coatings slide # 7

DRYING / CURING MECHANISM

The properties of a paint film is

closely related to how the
binder dries or cures.

The three most common drying

/ curing mechanisms are:
1. Physically Drying (solvent
evaporation)
2. Oxidatively Curing (reaction with
oxygen in the air)
3. Chemically Curing (chemical reaction
between base and hardener)

Frosio 08 Paints and coatings slide # 8

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Frosio course hand-out: Section 08 Paints and coatings

Physical drying

The solvents
evaporate
Molecules pack and
melt together to
form a paint film
No chemical bonds

Paint technology: Physical_drying1

Frosio 08 Paints and coatings slide # 9

Physical drying Waterborne paints

Water evaporating

= Dispersed droplets
Droplets are packing

Droplets melt together, co-solvents evaporate

Frosio 08 Paints and coatings slide # 10

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Frosio course hand-out: Section 08 Paints and coatings

Curing (drying) by oxidation

The solvents
evaporate
Oxygen enter the
paint and the
reaction starts
The binder
molecules link
together through a
chemical reaction
with oxygen
Paint technology: Oxidation_drying1

Frosio 08 Paints and coatings slide # 11

Chemical curing
The solvents evaporate
Component A and
Component B molecules
moves towards each
other
They link together
through a chemical
reaction
A three dimensional
network is formed which
give the solid paint film Paint technology: Curing_good1

Frosio 08 Paints and coatings slide # 12

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Frosio course hand-out: Section 08 Paints and coatings

Insufficient mixing of
two-pack paint

Proper mixing is a pre-

requisite to obtain proper
curing
Insufficient mixing makes
it impossible for the
molecules to come in
contact with each other
A three dimensional
network will not be
formed Paint technology: Curing_bad1

Frosio 08 Paints and coatings slide # 13

What factors may influence the drying

process ?

Relative humidity, % R.H.

Ventilation
Temperature
Film thickness
Number of coats
Evaporation rate of the
solvents

Frosio 08 Paints and coatings slide # 14

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Frosio course hand-out: Section 08 Paints and coatings

Curing Mechanism of some Binders

Oxidising
Alkyd
Physically drying
Chlorinated rubber
Vinyl
Acrylic Chemically curing
Latex Epoxy
Bitumen Polyurethane
Tar Polyester
A/F-polymers Vinylester
Silicate
Polysiloxane

Frosio 08 Paints and coatings slide # 15

Mixing of two-pack paints

Visual mixing control
It is difficult to verify
proper mixing when
the base is clear
A dark base makes it
easier to see when the
mixing is complete
Insufficient mixing
results in reduced
protective properties of
the paint system

Application: Mixingcontrol1

Frosio 08 Paints and coatings slide # 16

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Frosio course hand-out: Section 08 Paints and coatings

The dry binder consists of large

molecules

Large molecules gives:

a) Good mechanical strength
b) Good chemical resistance

Physically drying binders:

Molecules are large before drying starts

Chemically curing binders:

Large molecules are formed during curing

Frosio 08 Paints and coatings slide # 17

The surface tolerance depends on the

penetrating properties of the binder
Vinyl
Chlorinated rubber
Epoxy
Polyurethane

Urethane alkyd
Surface tolerant paint: Alkyd
Epoxy Mastic
Boiled linseed oil
Raw linseed oil

Frosio 08 Paints and coatings slide # 18

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Frosio course hand-out: Section 08 Paints and coatings

Surface tolerant paints are

recommended for uneven substrates

Most paints can be applied

to steel blast cleaned to Sa
2
Not all paints possess the
required wetting property
for successful application on
uneven substrates
Surface tolerant paints give
a longer life time on such
substrates Paint technology / Surface tolerant2

Frosio 08 Paints and coatings slide # 19

Epoxy Mastics are

Surface Tolerant and High build

Traditional paints
Low coverage
Steel Poor penetration

Epoxy Mastic
Good penetration
Steel High Build

Frosio 08 Paints and coatings slide # 20

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Frosio course hand-out: Section 08 Paints and coatings

Solvent Test
Can be used to identify drying
mechanism of unknown old coating
Expose the old coating to MEK solvent
for 10 15 minutes
Place paper towel / cloth / rags
soaked in the thinner on the coating
to be tested
Observe how the coating react

Frosio 08 Paints and coatings slide # 21

Solvent test: Three samples

Frosio 08 Paints and coatings slide # 22

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Frosio course hand-out: Section 08 Paints and coatings

Solvent test: Three samples

Use paper towel to keep the solvent in contact with the sample

Frosio 08 Paints and coatings slide # 23

Solvent test: Three samples

Paper-towels wetted by MEK

Frosio 08 Paints and coatings slide # 24

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Frosio course hand-out: Section 08 Paints and coatings

Solvent Test: Acrylic

(physically drying) Paint sample is dissolved

Frosio 08 Paints and coatings slide # 25

Solvent Test: Alkyd

(oxydatively curing)
Alkyd film lifting

Frosio 08 Paints and coatings slide # 26

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Frosio course hand-out: Section 08 Paints and coatings

Lifting and
loss of
adhesion,
solvent act as
paint remover.
Disregard
blue smear
from paper
towel

Frosio 08 Paints and coatings slide # 27

Solvent Test: Epoxy

(chemically curing) No change in paint sample

Frosio 08 Paints and coatings slide # 28

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Frosio course hand-out: Section 08 Paints and coatings

Solvents &
Diluents

Frosio 08 Paints and coatings slide # 29

Solvents / diluents

Dissolve the binder

Give lower viscosity
Give application properties
for brush, roller, spray
Once the paint has been
applied, there is no more
need for the solvent

Frosio 08 Paints and coatings slide # 30

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Frosio course hand-out: Section 08 Paints and coatings

Solvents / diluents , examples

Water
White Spirit
Xylen
Toluen
Ketones
Glycoles
Alcohols
Reactive solvents

Frosio 08 Paints and coatings slide # 31

Solvent / Diluent / Thinner

Solvent
Single or blended
Disolves the binder Thinner
completely Single or
(Forms a solution) blended
Used to lower
Diluent the viscosity
Single or blended Usually a
mixture of
Does not dissolve the
solvents and
binder
diluents
(Forms a mixture)
Used in conjunction
with solvents

Frosio 08 Paints and coatings slide # 32

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Frosio course hand-out: Section 08 Paints and coatings

The paint is supplied

with the correct viscosity
Usually there is no
reason to thin the
paint
The paint is
supplied at its
optimal viscosity
for being applied
Excessive thinning
may lead to
several problems. Paint technology / Thinning viscosity 1

Frosio 08 Paints and coatings slide # 33

Addition of thinner
Evaporation rate and solubility
of a thinner will influence a
paints:
Drying time
Film-forming properties
Quality of the film

Most paints are ready to be applied as

supplied by the manufacturer.
Never add an unspecified thinner to a paint,
it may lead to disastrous results

Frosio 08 Paints and coatings slide # 34

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Frosio course hand-out: Section 08 Paints and coatings

Addition of wrong type of thinner

A clear binder is poured
into the beaker
Wrong type of thinner is
added
This will change the
properties of the paint
film
The binder separates
The binder will no longer
be clear: Difficult to see
through
The same experiment is
carried out with correct
thinner: Good result Paint technology: Thinner_wrong1

Frosio 08 Paints and coatings slide # 35

Thinning the paint

Thinning is primarily only

recommended in three
situations:
Very cold paint (becomes
thick)
Very warm conditions /
substrate (keep the film open
longer)
Painting very porous
substrates (tie coat or mist
coat technique)

Frosio 08 Paints and coatings slide # 36

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Frosio course hand-out: Section 08 Paints and coatings

Excessive thinning may lead

to entrapped solvents
One thinned and one
unthinned sample of paint is
applied to a structure
To achieve the specified DFT
the thinned paint must be
applied to a higher WFT
After a certain period of time
the unthinned is fully cured
The solvents has not
evaporated from the thinned
paint.
If put into service the paint Paint technology/ Thinning entrapped1
will develop blistering

Frosio 08 Paints and coatings slide # 37

Thinning of the paint may

result in lower DFT
Two samples of the same
paint are applied to a steel
structure.
The WFT is the same for both
samples
One of the samples is thinned
During drying / curing of the
paint the thinners will
evaporate from the wet paint
film
The thinned paint contains a
lower volume solids and will Paint technology/ Thinning low dft1
give a lower DFT.

Frosio 08 Paints and coatings slide # 38

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Frosio course hand-out: Section 08 Paints and coatings

Thinning the paint may result in

the requirement of a longer
drying time
One thinned and one
unthinned sample of paint is
applied to a structure
To achieve the specified DFT
the thinned paint must be
applied to a higher WFT
After a certain period of time
the unthinned is fully cured
The solvents has not
evaporated from the thinned
paint.
Paint technology/ Thinning drying1

Frosio 08 Paints and coatings slide # 39

Volatile / Non-volatile

A paints Solid Content means the

part which does not evaporate,
commonly quoted as %volume.

A paints VOC (Volatile Organic

Compound) tells us how many grams
of solvents there are in one litre of
paint.

Frosio 08 Paints and coatings slide # 40

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Frosio course hand-out: Section 08 Paints and coatings

Solid Content

Solvents, 20%

Solvents, 50% Additives, 8%

Pigments, 24%

Additives, 5%

Pigments, 15%

Binder, 48%
Binder, 30%

Solid content: 50% Solid content: 80%

Frosio 08 Paints and coatings slide # 41

Solid content: WFT vs. DFT

When applied in the same WFT, the paint with the higher solid
content will result in a higher DFT (and thus need fewer coats
or gives better protection)

100 100
80 microns wetfilm
microns dry film
50 microns wetfilm
microns dry film

50% SOLID CONTENT 80% SOLID CONTENT

Frosio 08 Paints and coatings slide # 42

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Frosio course hand-out: Section 08 Paints and coatings

Pigments &
Powders

Frosio 08 Paints and coatings slide # 43

Colour Pigments
Natural or synthetic pigments
Organic or inorganic pigments
Gives colour to the film
Hides the substrate (opacity)
Almost all colours consist of a blend of
pigments
Individual colours can be changed or
adjusted by altering the pigment blend

Frosio 08 Paints and coatings slide # 44

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Frosio course hand-out: Section 08 Paints and coatings

Active / Reactive Pigments

Takes an active role in ensuring that
the paint perform as expected:
Anticorrosive
Red Lead
Zinc-chromate
Zinc-phosphate
Zinc-dust
Antifouling
Cuprous oxide
Rheology (Anti-sagging)
Bentonite clay

Frosio 08 Paints and coatings slide # 45

Extenders
Naturally occurring minerals, e.g.:
Dolomite
Talc (Talcum powder)
Chalk (Calcium Carbonate)
Clay (China Clay)

Reinforce and give body to the film

Varying hardness
White / grey in colour
Very little influence on colour of
the film (poor opacity)

Frosio 08 Paints and coatings slide # 46

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Frosio course hand-out: Section 08 Paints and coatings

The Gloss of a Paint Depends on the PVC

(Pigment - Volume - Concentration)

Binder Glossy
Colour PVC 15 -25
pigments
Extenders
Semigloss
PVC 30 - 40

Flat
PVC 35 - 50

Frosio 08 Paints and coatings slide # 47

Barrier pigments
Flake-shaped pigments
Tend to align themselves
parallel to the substrate
Reinforce the film
Increase the barrier effect of the
film
Often made from aluminium,
glass, micaceous iron oxide
(MIO or mica)

Frosio 08 Paints and coatings slide # 48

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Frosio course hand-out: Section 08 Paints and coatings

Barrier effect
Why are some paints pigmented
with aluminium or glass flakes ?

Water

Paint with glass or

aluminium flakes
Steel

Flake-shaped pigments make it more difficult for moisture

to reach the steel as the distance becomes longer.

Frosio 08 Paints and coatings slide # 49

Additives
Examples:
Wetting agent Many types:
Anti-foam Production enhancers
Improve manufacturing
Anti-settling
Anti-skin Storage facilitators
Storage stability
Anti sagging
Application aids
Catalysts Easier application
UV-absorbers Appearance improvers
Etc. Better gloss
Service life strengtheners
Resist fouling

Frosio 08 Paints and coatings slide # 50

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Frosio course hand-out: Section 08 Paints and coatings

Corrosion protection by paints

For corrosion prevention with paints, three main

principles are employed:

Barrier effect
Inhibitor effect
Galvanic effect

Frosio 08 Paints and coatings slide # 51

Corrosion protection by paints.

The barrier effect
When paint is applied to
a structure a barrier is
created between the
substrate material and
the surrounding
environment
A thick paint film will give
a better barrier than a
thin film
The barrier effect can be
further improved by
adding flake formed
pigments to the paint.
Paint technology/ Paint barrier effect1

Frosio 08 Paints and coatings slide # 52

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Frosio course hand-out: Section 08 Paints and coatings

Corrosion protection by paints.

The inhibition effect
The inhibition type of paints is
not an inert paint film as the
barrier coatings
The paints contain chemicals or
inhibitors
The inhibitors react with moisture
and the steel and forms a passive
layer close to the steel substrate.
The layer passivates the steel
and thereby reduce the corrosion
rate.
Examples:
Red Lead Primer
Zinc Chromate Primer Paint technology/ Paint inhibition effect1
Zinc Phosphate Primer

Frosio 08 Paints and coatings slide # 53

Corrosion protection by paints.

The cathodic protection effect
Some paints offer the same
cathodic protection effect as
sacrificial anodes
The CP type of paints is not
an inert paint film as the
barrier coatings
The paints contain active,
metallic pigments
The pigments react with
moisture and the steel and
creates a calcareous deposit
on bare spots of the the steel
substrate.
Paint technology/ Paint CP effect2

Frosio 08 Paints and coatings slide # 54

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Frosio course hand-out: Section 08 Paints and coatings

Water absorption.
Different types of paint

Coating type Thickness Grams/m/24 hours

Epoxy Polyamide 125 m 1.71

Amine Catalysed Epoxy 125 m 3.10
Vinyl Chloride-Acetate 125 m 11.94
Vinyl Acrylic 125 m 12.87
Alkyd (Short Oil) 125 m 57.36

This is why alkyd paints are not suitable for submerged service
(they adsorb too much in water, leading to swelling of the film)

Frosio 08 Paints and coatings slide # 55

What is a shopprimer?

Frosio 08 Paints and coatings slide # 56

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Frosio course hand-out: Section 08 Paints and coatings

Shopprimers
Definition:
A quick drying material applied as a thin film to a
metal surface after cleaning, e.g. by a blast
cleaning process, to give protection during the
period before and during fabrication.

Requirement:
Must not interfere with the speed or quality of
cutting and welding of the steel during fabrication,
so DFT must be limited to:
Iron oxide: 15 20 micr.
Zinc-rich: 10 15 micr.

Frosio 08 Paints and coatings slide # 57

Activities involved in shop priming

Cleaning
Blasting
Application
Handling

Shopprimer/Shopplant1

Frosio 08 Paints and coatings slide # 58

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Frosio course hand-out: Section 08 Paints and coatings

Shop primers - history

Iron oxide PVB

Iron oxide two pack epoxy
PVB
Zinc epoxy Not suitable for
1st. generation Zinc silicate submerged service

2nd. generation Zinc silicate Iron oxide

Lower corrosion classes
3rd. generation Zinc silicate
Zinc
High temperature Zinc silicate
Higher corrosion
Water borne shopprimer classes
Water borne Zinc silicate

Frosio 08 Paints and coatings slide # 59

Shopprimer history
Initially:
Only temporary protection
Removed by blast cleaning before painting
Later:
Improved quality
Blast cleaning only of welds and damages
Todays technology
UHPWJ before painting

Shopprimer may now be a part of

the long term protection paint system

Frosio 08 Paints and coatings slide # 60

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Frosio course hand-out: Section 08 Paints and coatings

Antifoulings

Frosio 08 Paints and coatings slide # 61

What is fouling ? (1 of 2)

Fouling is the settlement and

growth of marine plants
and animals on surfaces
(including man-made
structures) in the sea

Frosio 08 Paints and coatings slide # 62

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Frosio course hand-out: Section 08 Paints and coatings

What is fouling ? (2 of 2)
There are an estimated 4 - 5000
fouling species and these can be
classified into:

Microfouling
generally referred to as slime, a complex viscous
mixture of bacteria and microscopic organisms

Macrofouling
which includes animals and plants

Frosio 08 Paints and coatings slide # 63

How does fouling happen?

Free floating or free swimming spores
and larvaes follow the currents, tides
and waves.
They have the opportunity to contact
suitable surface when the time comes.
Fouling happens when these larvaes or
spores settle and develop into an adult,
small at first but steadily growing.

Frosio 08 Paints and coatings slide # 64

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Frosio course hand-out: Section 08 Paints and coatings

Micro-fouling
Micro photo of Cypris stage of
Diatoms barnacles life cycle

CD 1545 nr. 6 CD 1545 nr. 8

Frosio 08 Paints and coatings slide # 65

Macro-fouling
Hydroids Barnacles

CD 1545 nr. 12 CD 1545 nr. 5

Frosio 08 Paints and coatings slide # 66

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Frosio course hand-out: Section 08 Paints and coatings

Macro-fouling
Cristalea, found in Norway

CD 1545 nr. 14

Frosio 08 Paints and coatings slide # 67

Fouling on flatbottom
Goose neck barnacles

CD 1545 nr. 15

Frosio 08 Paints and coatings slide # 68

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Frosio course hand-out: Section 08 Paints and coatings

The Purpose of Antifoulings

9 To prevent or reduce growth
9 To provide better fuel economy over the
sailing period
9 To avoid growth penetrating the coating and
thereby extend corrosion protection

Frosio 08 Paints and coatings slide # 69

The consequences of fouling

On a ships hull
Increased fuel consumption
On a marine structure
Increased drag Heavier
load on the structure
Structural failures
Seawater pipe systems
Increased corrosion
Reduced pipe diametres
Pump failures

Frosio 08 Paints and coatings slide # 70

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Frosio course hand-out: Section 08 Paints and coatings

Why do ships need

anti-fouling systems?

Fouling leads to an increase in fuel consumption

of up to 40%, due to the increase in drag resistance

A clean ship sails faster and with less energy

Fouling will eventually damage the primer system

Frosio 08 Paints and coatings slide # 71

The composition of Antifoulings

Binder
Biocide ?
Extenders
Pigments
Solvents
Additives

Frosio 08 Paints and coatings slide # 72

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Frosio course hand-out: Section 08 Paints and coatings

Conventional Antifoulings
Soluble matrix paints
Rosin as a binder
Approximately 12 months protection
Binders dissolves in water and biocide is
released
Examples: A/F Tropic, A/F Super Tropic etc.

NOTE:
Danger of cracking and flaking
Needs to be quickly immersed in water

Frosio 08 Paints and coatings slide # 73

Long-life Antifouling
Insoluble matrix paints
Only biocides are released
Effective protection is up to 24
months
Leaves weak substrate for
subsequent coat (leach layer)
Sealer coat normally required
Binder: CR, Vinyl (possible to add
small amount of colophonium)
Example: A/F Sargasso

Frosio 08 Paints and coatings slide # 74

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Frosio course hand-out: Section 08 Paints and coatings

Long-life Antifouling
Binder:
CR, Vinyl
(Possible to add small amount
colophonium)

Biocide:
Cuprous oxide, Organotin (TBTO), etc

Life time
12 - 24 months

Often called:
Sargasso etc.

Frosio 08 Paints and coatings slide # 75

Self polishing Antifoulings

Predictable performance
Extended dry docking period
Control of roughness and
smoothing
No sandwich coatings
problems
Fouling control due to linear
biocide release
Lifetime directly proportioned
with dry film thickness

Frosio 08 Paints and coatings slide # 76

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Frosio course hand-out: Section 08 Paints and coatings

Self-polishing Antifoulings
Types of self-polishing antifoulings:

Hydrating
Polishes through erosion, no smoothing effect

Hydrolysing
Chemical reaction in seawater, self-smoothing effect

Hybride
Combination of hydrating and hydrolysing binders,
giving limited self-smoothing effect

Frosio 08 Paints and coatings slide # 77

Hydrating Antifouling

Water sensitive and

water soluble
binders
Non constant
erosion rate
Builds up a soft
leach layer
No improvement of
smoothness on hull Antifouling \ Hydrating1

Frosio 08 Paints and coatings slide # 78

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Frosio course hand-out: Section 08 Paints and coatings

Cross section of hydrating

antifouling

Polishing
(erosion) Epoxy seal

Soft leach layer Antifouling

Primer

Frosio 08 Paints and coatings slide # 79

Hydrolysing Antifouling

Chemical reaction
between antifouling
and seawater
Surface peaks
erode faster
Improves
smoothness of hull

Antifouling \ Hydrolysable1

Frosio 08 Paints and coatings slide # 80

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Frosio course hand-out: Section 08 Paints and coatings

Cross section of hydrolysing

antifouling

Epoxy seal

Reduction
in
thickness CD 1118 nr. 44 Antifouling
after
polishing

Primer

Frosio 08 Paints and coatings slide # 81

Why is hydrolysis so important ?

Because:
Linear erosion rate assures long term
antifouling property
No porous leach-layer means good
adhesion after over-coating
Continuous smoothing of the surface
ensures good fuel efficiency
Hard film maintains its good appearance

Frosio 08 Paints and coatings slide # 82

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Frosio course hand-out: Section 08 Paints and coatings

Cross section of hybride antifouling

Epoxy seal Polishing

Antifouling Leach layer

Primer

Frosio 08 Paints and coatings slide # 83

Release rate for Antifoulings

Comparison of release rate of biocide for different A/F-types
Release rate (g/cm2 / day)

40
Conventional A/F

30
Minimum release
Long life A/F level for
fouling protection
30 Self polishing A/F

10

1 2 3 Time, years

Frosio 08 Paints and coatings slide # 84

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Frosio course hand-out: Section 08 Paints and coatings

Anti-fouling for Aluminium hulls

Special requirements:
Must be free from Copper
Metallic Copper in contact with
aluminium will cause bi-metallic
corrosion, perforating the hull plates
in very short time

Must perform at speeds up to 50

knots (e.g. for catamarans)
Preferably self-polishing type (best
performance)

Frosio 08 Paints and coatings slide # 85

A paint system may be

compared to a house

First: Second:
The basement - Primer coat One or several stories - Midcoats

They all have a special function

Finally: In the house
The roof - Top coat In the paint system
Frosio 08 Paints and coatings slide # 86

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Frosio course hand-out: Section 08 Paints and coatings

Primers

Primers are universal for most anticorrosive coating

systems and are considered the most important
component of the system. The most important
properties of primers are listed as follows:

1. Adhesion (strong bonding to substrate).

2. Cohesion (high internal strength in the film).
3. Inertness (strong resistance to corrosion and chemicals).
4. Intercoat bond (high bonding to intermediate coat).
5. Appropriate flexibility.

Frosio 08 Paints and coatings slide # 87

Intermediate
or Body coats

The principal purposes of an

intermediate coat is to provide:

1. Thickness for total coating.

2. Strong chemical resistance.
3. Resistance to moisture vapour transfer.
4. Increase electrical resistance for the coating
system.
5. Strong cohesion.
6. Strong bonding to primer and topcoat.

Frosio 08 Paints and coatings slide # 88

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Frosio course hand-out: Section 08 Paints and coatings

Topcoats

Topcoats also perform several

important functions as they:

1. Provide a resistant seal for the coating system.

2. Form the initial barrier towards the environment.
3. Provide resistance towards chemicals, water, and
weather.
4. Provide a tough and wear-resistant surface.
5. Provide a pleasing appearance.

Frosio 08 Paints and coatings slide # 89

What film-thickness should

corrosion protecting paint systems have ?

Deciding factor is the environment:

In a dry inland atmosphere and indoor 120 microns will be
sufficient. In an aggressive industrial environment and along
the coast and at sea, 250 - 300 microns will be necessary.
Number of coats is also of importance and not only
the film thickness
100 microns in 2 coats (50 + 50 microns) are giving better
protection than 100 microns in 1 coat. Special coatings may
be applied in thick coats.

Frosio 08 Paints and coatings slide # 90

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Frosio course hand-out: Section 08 Paints and coatings

Generic types of paint

Frosio 08 Paints and coatings slide # 91

Alkyd Paints
Advantages Limitations
Good application properties Poor chemical resistance
(especially against alkaline)
1-component
Limited water resistance
Good weather durability
(submerged)
Good wetting properties
Limited solvent resistance
Good recoatability
Limited film thickness per
Good levelling properties coat
Good gloss retention Poor adhesion to CR
Dry heat resistant up to 120 Never to be used on Zinc
C.

Frosio 08 Paints and coatings slide # 92

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Frosio course hand-out: Section 08 Paints and coatings

Modified Alkyd paint

Styrene alkyds - Quicker drying, need
stronger solvent

Silicone alkyds - better gloss retention

Urethane alkyds - Quicker drying, better water

and chemical resistance. Can
be applied in thicker coats
(60-100 microns DFT)

Frosio 08 Paints and coatings slide # 93

Chlorinated Rubber Paints

Advantages Limitations
Physically drying Poor solvent resistance
Not temperature Low solid content
dependent Relatively poor wetting
Easy to recoat properties
One component Thermoplastic
Very good water Dry heat resistant up to
resistance approx. 70 C
Relatively good
chemical resistance

Frosio 08 Paints and coatings slide # 94

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Frosio course hand-out: Section 08 Paints and coatings

Vinyl paints
Advantages Limitations
Physically drying Low solid content
High chemical resistance Poor resistance against
Good water resistance strong solvents
Quick drying Dry heat resistant up to
Not temperature dependent approximately 80 C
One-component

Used for:
Exterior objects above water
Offshore on top of Zinc-ethylsilicate

Frosio 08 Paints and coatings slide # 95

Pure Epoxy Paints

Advantages Limitations
Chemical curing Chalking
Very good chemical Temp. dependent
resistance 2 - component
High alkali resistance Requires blast cleaning
Moderate resistance to acids Overcoating time
Good adhesion
Very low permeability
High mechanical strength
Dry heat resistant up to 120

Frosio 08 Paints and coatings slide # 96

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Frosio course hand-out: Section 08 Paints and coatings

Vinyl Tar - Modified type

Advantages Disadvantages
Higher content of Bleeding
solids Dark colours
Higher water Tar on cancer list
resistance
Better wetting
properties
Cost advantages
Used for:
Under water areas

Frosio 08 Paints and coatings slide # 97

Acrylic Paints
Advantages Limitations
Physically drying High VOC
Not temperature Poor solvent resistance
dependent Low solid content
Easy to recoat Relatively poor wetting
One component properties
Good water resistance Thermoplastic
Relatively good chemical
resistance
Good weather resistance
Replaces CR & Vinyls

Frosio 08 Paints and coatings slide # 98

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Frosio course hand-out: Section 08 Paints and coatings

Curing agents for Epoxy Paints

Polyamides:
Normal epoxy paints

Amine and amine adduct:

Solvent free coatings
Tankcoating

Isocyanates:
Low temperature curing
Reaction with -OH

Frosio 08 Paints and coatings slide # 99

Epoxy Paints- General

Curing Diagram
Temperature, C
40

30

20

10

0
2 4 7 14 28
Curing time, days

Frosio 08 Paints and coatings slide # 100

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Frosio course hand-out: Section 08 Paints and coatings

Epoxy Coal Tar

Advantages: Limitations:
Chemically curing Dark colour
More flexible Temp. dependent
Excellent water resistance 2-component
Better wetting properties Recoating interval
Dry heat resistant up to Bleeding when recoated
90 C
Coal Tar is carcinogenic

Frosio 08 Paints and coatings slide # 101

Epoxy Mastic Paints

Advantages: Limitations:
Surface tolerant. Chalking. Not UV -
High solids. resistant
High build. Temperature
Reduced application dependent for curing
time (less cost). Do not apply on thick
Environmentally friendly. layers of physically
drying paints
Minimum DFT 150
microns by airless
spray

Frosio 08 Paints and coatings slide # 102

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Frosio course hand-out: Section 08 Paints and coatings

Epoksy Acrylic (Two-Pack Acrylic)

Advantages Limitations
Very good weather 2-pack
resistance
Very good gloss retention Recoating:
Very good chemical Early versions:
resistance before 12 hours or
Very good solvent after 5 days at 23 C
resistance
New versions: no
Cures down to 0 C
particular restrictions
Potlife (24 timer)
Performance comparable
to Polyurethane, but
without using Isocyanate

Frosio 08 Paints and coatings slide # 103

Polyurethane Paints

Advantages Limitations
Very good weather 2-pack
resistance May cause skin irritation
Excellent gloss Overcoating time
durability
Very good chemical
resistance
Very good solvent
resistance
Cures down to 0 C

Frosio 08 Paints and coatings slide # 104

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Frosio course hand-out: Section 08 Paints and coatings

Zinc Epoxy
Advantages Limitations
Chemically curing Temperature dependent
Good corrosion protection 2-component
Good adhesion Film thickness: 25 - 50 Pm
Require min. Sa 2 Not acid- and alkaline
Good mechanical strength resistant
May be recoated with all (Resistant between pH 5-9)
types of paint, except Alkyd
Dry heat resistant up to
120 C

Frosio 08 Paints and coatings slide # 105

Zinc Ethyl-silicate Paints

Advantages Limitations
Very good solvent resistance Requires humidity for
curing
Very high heath resistance
2-pack
(max 400 oC)
Max. DFT: 100 m
Very high mechanical
strength At higher DFT tendency
of mud-cracking or
Very good adhesion to blast
checking
cleaned steel
Relatively good recoatability

Frosio 08 Paints and coatings slide # 106

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Frosio course hand-out: Section 08 Paints and coatings

Glass-flake Reinforced Polyester

Advantages Limitations
Quick curing Temperature dependent
Variable curing time Short potlife
Application with airless Recoating interval
Excellent mechanical strength 2 - 12 hours
Glass-flakes reduce shrinkage, Bad curing may be
increases mechanical strength experienced on Zinc
and water resistance. primers and galvanised
surfaces.
Very good chemical resistance

Frosio 08 Paints and coatings slide # 107

Vinyl ester coatings

Advantage Limitation
Very fast curing Short potlife (approximately
Very good adhesion 45 minutes)
Very good abrasion Overcoating interval:
resistance - Min. 2 hours, max. 24
Very good chemical hours.
resistance Limited shelf-life
Very good solvent - Approximately 6 months
resistance at 23 C
Can be applied by normal
Dependent on temperature
airless spray
during application
Glassflakes improve
abrasion resistance Only to be applied on blast-
cleaned steel (Sa 2 )

Frosio 08 Paints and coatings slide # 108

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Frosio course hand-out: Section 08 Paints and coatings

Heat Resistant Paints:

Aluminium silicone:
Resistant up to approximately 600C
Zinc silicone:
Resistant up to approximately 400C

Remember:
To be applied on Sa 2
To be applied in thin coats only (20 m)
Heavier coats may give blistering
Zinc silicate must be fully cured before overcoating

Frosio 08 Paints and coatings slide # 109

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