This document discusses special effect pigments used in aerospace coatings. It provides a history of special effect pigments dating back to 1655 and describes the different types including metallic and mica flake pigments. It explains how these pigments produce effects like interference and iridescence through their layered structures and interactions with light. Evaluation criteria for these pigments include durability, sprayability, reparability, price, and weight. Examples are given of airlines that have selected mica pigments for use on their aircraft fleets.

1. AEROSPACE COATINGS
Ana Ricardo
Especialista de Pintura de Aviões
TAP Manutenção & Engenharia
Pigmentos com Efeitos Especiais

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2003 – Celebrando 1 século de voo…
Desde…
… até.
Em 100 anos.

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Introdução
• História
• Pigmentos com efeitos especiais
• Critérios utilizados na avaliação de um efeito pigmento / cor particular
• Exemplos

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História
Abr 1655
1917
1920
1940
1942
1970
1984
Presente
• Isolamento de substância brilhante prateada proveniente das
escamas de peixe e início da produção industrial na Europa de
lustrinas perladas
• Descoberta de que o efeito das lustrinas perladas é um
fenómeno óptico, tendo por base a disposição horizontal de
camadas finas, umas sobre as outras
• Primeira síntese da suspensão de lustrinas perladas
• Primeira produção de PbHPO4 em forma de plaquetas
• F.C. Atwood descreve a combinação de mica e TiO2 para o efeito
das lustrinas perladas
• Produção de pigmentos de mica - TiO2
• Aplicação de pigmentos de óxidos metálicos para Revestimentos
em OEM. Aceitação desta classe de pigmentos por todas as
indústrias de pigmentos e de tintas.
• Todos os anos mais pigmentos com efeitos especiais, ficam
disponíveis

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Pigmentos com efeitos especiais
• Tipos de pigmentos com efeitos especiais
• Química destes pigmentos
• Como avaliar uma cor
• Critérios utilizados para avaliar um efeito cor / pigmento particular

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Tipos de pigmentos com efeitos especiais
Sólidos
• revestimentos homogéneos (particles < 1 µm)
Effect pigments
• presença de flocos (partículas de > 5 µm)
• 1ª classe / tipo (cintilante / efeito metálico)
• 2ª classe / tipo (cores com interferência)

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Efeito dos pigmentos
• Efeito cintilante
• Efeito interferente

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Effect pigments - types
Roughly categorised effect pigments:
• Metallic pigments consist of very thin metallic flakes or wafers that
act as miniature mirrors. Their intensity changes according to the
angle from which they are viewed. Maximum light intensity is achieved
near the gloss, the angle at which the incident light is reflected.
Minimum light intensity is experienced at an angle far away from the
gloss.
• Mica flake effect pigments with single or multiple thin layers of metal
oxide. The interplay of colours produced by these pigments is due to
the layered structure of the metal oxide, which is also responsible for
the rich deep glossy effect.

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Chemistry special effect pigment
Mica
Cross-section through a silica flake
coated with a-Fe2O3 (Hematite)
Electron micrograph of Al2O3 flakes
Mica – raw material

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SEM picture (top view) showing an
Industrially produced iron oxide mica pigment
Transmission electron microscopic picture (TEM) showing a cross-section
of an industrially produced iron oxide on α-Al2O3 substrate
SEM photo of a cross-section through an anatase/mica pigment particle.
The anatase layers are precipitated to yield an average thickness of
140 nm on each side of the mica substrate for a blue interference colour

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Interference explained
d
glimmerplate
TiO2-layer
R2R1
reflection
I0
Light
α
normal
transmision
β
B
D
CA
2 2
2 2
δ n(AB BC) AD
δ 2d n s
d n
inα
λ
Δ 2 i αs n
2
= + −
= −
= − +
The resulting color depends on:
• Layer thickness of the TiO2
• Refraction index
• Angle of incidence of the light.

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Influence subject
1thin coat Several thin coats

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Influence of layer thickness
0
100
200
300
330nm 420nm 510nm 600nm 690nm
R [%]
golflengte λ
45° belichting/120° waarneming
9103
9205
9215
9235
9225
Increasing the layer thickness
of TiO2 results in color shifts
Towards larger wavelengths.

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Influence of layer thickness
Branco prateado
Dourado Interferente
Encarnado Interferente
Azul Interferente
Verde Interferente

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Overview mica special effect colors

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Interference color
Sample 18: Chromaflair 230M M13
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80
a
b
40/-10
10/-10
20/-10 30/-10
60/-10
50/-10
45/-10
70/-10

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Perception special effect colors
Color is the perception which is formed in the brain of
the observer via the eye, brought about by rays
of light which are reflected or transmitted by
homogeneous objects
Texture is the visible surface structure depending on the
size and organization of small constituent parts of a
material.

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How to evaluate a special effect color
• at large distance only color!
• at microscopic level no match is required!
– orange pigment can be imitated by a combination of a red
and yellow
5 m 5 cm 50 µm

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Evaluation color
Model defined in 1976 by CIE
CIE = Commission Internationale de l’Eclairage

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How to evaluate special effect color
• Classical: tilting simply simulates changes from a fixed light
source and does not take any account of colour shifts produced
through interference
• Modern: To allow interference shifts to be observed, the panel
must be moved so as to allow the angle to the light source to be
made steeper or flatter

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Criteria used for evaluation to a particular pigment / color
effect
• Durability pigment
– Chemical resistance
– Light fastness
• Sprayability – uniform film
• Reparability (spot repair)
• Price
• Weight

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Gulf Air – Selected Aviox Mica for whole fleet

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Germanwings- Mica success in maintenance

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Gulf Traveller- Mica success in maintenance

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Airbus Customer Aeroflot

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Airbus Customer- North West

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