Novel corrosion inhibiting coating technology for the ... . Corrosion Inhibiting Technology... · Novel corrosion inhibiting coating technology for the protection of aluminum alloys

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  • Novel corrosion inhibiting coating technology for the protection of aluminum alloys

    Peter Visser

    15 June 2011

    AkzoNobel Aerospace Coatings

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

    2

    Introduction

    The Aerospace industry is relying on chromatedtechnologies for many years

    Strong drive for Chromate replacement

    Legislation (REACH)

    Health Safety and environmental concerns

    Sustainability and eco-efficient developments

    Chromated technology is still being used to achieve key performance characteristics.

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

    3

    Are chromates still needed for key performance using chrome free coating technology?

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

    4

    Pitting CorrosionPitting Corrosion

    Fast development of long and highdensity filiform corrosion

    Fast development of long and highdensity filiform corrosion

    Rapid development of corrosion Early formation of blisters along scribesExcessive formation of corrosion products

    Rapid development of corrosion Early formation of blisters along scribesExcessive formation of corrosion products

    The Challenge:Development of total chrome free coating solutions.

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

    5

    The Challenge:Development of total chrome free coating solutions.

    State of the Art corrosion inhibitorsmake it very difficult to comply withthe long term corrosion requirementsof the industry.

    Too low or high Solubility

    Compatibility with coatings system

    Insufficient passivation

    Specific activity

    Inconsistent performance

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

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    New approaches are needed to provide

    total chrome free coating solutions

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

    7

    New Approach total chrome free TechnologyMagnesium Rich Primer Technology

    Technology based on Magnesium metal particles as corrosion inhibitor

    The anti-corrosive propertiesof this coatings is basedon two different mechanisms:

    Cathodic protectionprovided by Mg metal powder

    Barrier protectionprovided by the binder andprecipitated Mg oxides (1)

    Significant departure from traditionalmethods and mechanisms ofcorrosion protection in aerospaceindustry

    100m100m100m

    0 2000 4000 6000T, s

    -1.6

    -1.4

    -1.2

    -1.0

    -0.8

    -0.6

    -0.4

    OCP

    , V

    Extent of Cathodic ProtectionExtent of Cathodic ProtectionDeveloped in MgDeveloped in Mg--rich Primersrich Primers

    AA2024

    AA7075

    0 2000 4000 6000T, s

    -1.6

    -1.4

    -1.2

    -1.0

    -0.8

    -0.6

    -0.4

    OCP

    , V

    Extent of Cathodic ProtectionExtent of Cathodic ProtectionDeveloped in MgDeveloped in Mg--rich Primersrich Primers

    AA2024

    AA7075

    Non-coated Bare

    Coated Bare

    Magnesium

    0 2000 4000 6000T, s

    -1.6

    -1.4

    -1.2

    -1.0

    -0.8

    -0.6

    -0.4

    OCP

    , V

    Extent of Cathodic ProtectionExtent of Cathodic ProtectionDeveloped in MgDeveloped in Mg--rich Primersrich Primers

    AA2024

    AA7075

    0 2000 4000 6000T, s

    -1.6

    -1.4

    -1.2

    -1.0

    -0.8

    -0.6

    -0.4

    OCP

    , V

    Extent of Cathodic ProtectionExtent of Cathodic ProtectionDeveloped in MgDeveloped in Mg--rich Primersrich Primers

    AA2024

    AA7075

    Non-coated Bare

    Coated Bare

    Magnesium

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

    8

    Magnesium Rich Primer technology combined with appropriate chrome free pretreatments and topcoats provide a fully chromate-free system which exceeds the corrosion capabilities of commercial and military standard products.

    Filiform corrosion development (EN3665) (2024 T3 Unclad, Scotch Brite solvent cleaned)

    012345678

    0 500 1000 1500 2000Hours

    max

    . len

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    (mm

    )

    chromate inhibitor MGRP

    2000h NSS (ASTM B-117)-Full chromate stack-up Total Chrome free System MgRP

    New Approach total chrome free TechnologyMagnesium Rich Primer Technology

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

    9

    New Chrome free coating technology

    A new patented chrome free coatings technology has been developed providing:

    Active inhibition of filiform corrosion

    Fast and effective passivation mechanism in Neutral Salt Spray

    Robust performance over clad and unclad substrates.

    Total chrome free coating systems meeting Aerospace requirements

    Universal Use

    Independent from resin technology

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

    10

    Meeting the Challenge

    Long term corrosion protection

    in

    Neutral Salt Spray and Filiform corrosion

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

    11

    Meeting the challenge:Resistance to Filiform Corrosion.Focus of new chrome free developments:

    Low corrosion rate

    Reduced distribution of corrosion (morphology & area)

    Process of Filiform corrosion

    Filiform corrosion development (EN3665) (2024 T3 Unclad TSA)

    0

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    Time (h)

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    inhibitor 1inhibitor 2inhibitor 3inhibitor 4New technologychromate

    Initiation/activation Nucleation Growth /Propagation

    Nucleation Growth

    Growth

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

    12

    Meeting the challenge:Neutral Salt Spray (ASTM B-117)

    Development strategy to meet the challenge of long term Neutral Salt Spray exposure:

    Corrosion inhibitor with leaching properties

    Fast and effective passivation mechanism in the scribe

    Irreversible nature passivation layer.

    Maintain coating integrity

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

    13

    The corrosion performance of the new chrome free coatingtechnology has been studied in a High Solids coatingsystem suitable for Aerospace applications

    Comparison against chrome free inhibitors and Chromates Primer / top coat systems Currently used chrome free pretreatments

    Meeting the challenge with chrome free coating technology

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

    14

    Active inhibition of Filiform corrosion (EN3665)

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

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    Example 1: Filiform performance on 2024 T3 UncladPretreatment: Scotch Brited / solvent cleaned

    The New Technology provides:

    Lower corrosion rate

    Shorter filamentsNew Technology ChromateNew Technology ChromateTechnology Chromate

    2000 h Filiform2024 T3 Unclad SB/SC

    Filiform corrosion development (EN3665) (2024 T3 Unclad Scotch Brited/ Solvent cleaned)

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    0 500 1000 1500 2000Exposure time (h)

    max

    . len

    gth

    filam

    ent (

    mm

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    inhibitor 1

    inhibitor 2

    inhibitor 3

    inhibitor 4

    New technology

    chromate

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

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    New Technology provides:

    Low corrosion rate

    Shorter filaments

    Example 2: Development Filiform Corrosion(EN 3665) 2024 T3 Clad- Solgel

    Filiform corrosion development (EN3665)(2024 T3 Clad- Solgel)

    0

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    0 500 1000 1500 2000

    Exposure Time (h)

    Max

    . len

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    filifo

    rm (m

    m)

    Inhibitor 1

    Inhibitor 2

    Inhibitor 3

    Inhibitor 4

    New Technology

    Chromate

    2000 h Filiform 2024 T3 Clad Sol gel

    Chromate New Technology

    2000 h Filiform 2024 T3 Clad Sol gel

    Chromate New Technology

    2000 h Filiform 2024 T3 Clad Sol gel

    Chromate New Technology

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

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    Example 3: Development Filiform Corrosion(EN 3665) 2024 T3 UnClad-TSA

    New Technology: Lower Corrosion rate and shorter filaments

    Filiform corrosion development (EN3665) (2024 T3 Unclad TSA)

    0

    1

    2

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    4

    5

    6

    0 500 1000 1500 2000

    Time (h)

    max

    . len

    gth

    filam

    ent (

    mm

    )

    inhibitor 1inhibitor 2inhibitor 3inhibitor 4New technologychromate

  • Novel corrosion inhibiting coating technology for the protection of aluminum alloysCopyright AkzoNobel 2011

    18

    Using Imaging

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