ANTI-ICING COATINGS1 Icing chamber developed at

Fraunhofer IFAM.

2 Analysis of the frost layer using

a measuring comb.

Ice formation on surfaces –

A major challenge

The icing of surfaces is a major and recur-

rent problem which impairs the function of

those surfaces and incurs costs. Consider,

for example, the surfaces of aircraft, ships,

rail vehicles, cars, roller shutters, refrige-

rators, and wind turbines. The effects of

icing include increased weight, impaired

function of equipment, longer maintenance

times and downtimes, and even damage to

persons.

Iced up rotor blades on wind turbines, for

example, result in significantly reduced

energy output. Ice falling off surfaces is

also a danger to people. One strategy to

reduce icing is to use so-called rotor blade

heating systems (hot air or hot wires). Here

the rotor blades of the stationary turbine

are heated so that adherent ice falls off.

During this de-icing period the wind tur-

bine actually consumes power rather than

produces power.

An optimal solution would be a coating on

the rotor blades which prevents ice formati-

on from the outset. The currently available

commercial anti-icing coatings cannot

effectively prevent ice formation on rotor

blades. The latest research strategies are,

however, showing great promise for solving

this problem.

Expertise of Fraunhofer IFAM –

Development and testing of

anti-icing coatings

Development of coatings

New techniques for the nano-struc-

turing of surfaces and their anti-icing

effect

Biomimetic anti-icing coatings based

on anti-freeze proteins

Temporary anti-icing coatings

Hydrophobic coatings

Fraunhofer Institute for

Manufacturing Technology

and Advanced Materials IFAM

- Adhesive Bonding Technology

and Surfaces -

Wiener Straße 12

28359 Bremen, Germany

Institute director

Prof. Dr. rer. nat. Bernd Mayer

Contact

Paint/Lacquer Technology

Dr. Volkmar Stenzel

Phone +49 421 2246-407

volkmar.stenzel@ifam.fraunhofer.de

www.ifam.fraunhofer.de

© Fraunhofer IFAM

F r A u n h o F E r - I n S T I T u T F ü r F E rT I g u n g S T E c h n I k u n D A n g E wA n D T E M AT E r I A l F o r S c h u n g I FA M

1 2

3 Evaluation of frost adhesion using the frost

adhesion test developed at Fraunhofer IFAM.

4 Test device developed at Fraunhofer IFAM

for carrying out the runback ice test on wing

sections.

3 4

Ice formation – current research

Three different icing scenarios are being

researched:

Frost adhesion test for simulating fros-

ting (Fig. 2 + 3)

Ice-rain test which simulates ice forma-

tion from rainwater

Runback ice test on wing sections (Fig. 4)

All the tests are carried out in the icing

chamber of Fraunhofer IFAM.

Frost adhesion test

Innovative testing technology is supporting

the development of novel anti-frosting coa-

tings. The frost layer that forms is analyzed

using a measuring comb (Fig. 2). The frost

adhesion is then evaluated in the so-called

frost adhesion test, a force test developed

at Fraunhofer IFAM (Fig. 3). It measures the

force required to detach the frost layer.

Ice-rain test

Extensive systematic studies at Fraunhofer

IFAM have shown that superhydrophobic

coatings give ice-free surfaces in the ice-

rain test. This anti-icing effect is, amongst

other things, due to the water-repelling

nature of the surface which hinders the

adhesion of water. The hydrophobicity of

a coating is hence a suitable, albeit not the

sole, parameter for an anti-icing surface.

runback ice test

Runback ice is a phenomenon that occurs

on wing sections of aircraft when thermal

de-icing systems are used. These systems

only de-ice the front edges of the wings.

The melted ice is forced backwards by the

flow of air, where some of this refreezes.

A test device has been developed at

Fraunhofer IFAM which allows this pheno-

menon to be studied (Fig. 4).

new r&D strategies

The Paint/Lacquer Technology section at

Fraunhofer IFAM is currently working on

a variety of strategies for minimizing ice

formation. The extensive knowledge of

surface pre-treatment, coating develop-

ment, and testing is being utilized for

this, as is other internal Fraunhofer IFAM

expertise in the area of plasma technology

for modifying surfaces. Complementing

the aforementioned tests, computer-aided

simulation methods are also being used

to evaluate the adhesion and detachment

mechanisms of ice and frost on coating

surfaces. The findings are allowing accele-

ration of the development work.

Anti-icing tests for coatings

Icing chamber at Fraunhofer IFAM

The novel icing chamber that has been

developed at Fraunhofer IFAM (Fig. 1)

can mimic almost any icing scenario on

surfaces and coatings.

It allows:

Air temperatures down to -20 °C

Substrate temperatures down

to -40 °C

Relative air humidities up to 40 %

Rain simulation via a nozzle system

Maximum wind speeds up to 70 m/s

Visual monitoring via a webcam

Icing test stand –

Testing under real conditions

Coating systems that have been suc-

cessfully tested in the icing chamber are

exposed to the outside weather in an

endurance test. This icing test stand is

on the Brocken in the Harz Mountains

at a height of 1141 meters. The results

attained in the icing chamber in the

laboratory have been found to agree

with the tests under real conditions.