Anticorrosive zn free pigments their performance
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Anticorrosive Zn Free Pigments: Their Performance. PNWSCT 2014. Agenda. Historical Evolution of Anticorrosive Pigments Corrosion Protection Zn free pigments Case Study Accelerated cyclic electrochemical test Analytical experiments Additional systems tested Summary.

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Anticorrosive zn free pigments their performance

Anticorrosive Zn Free Pigments: Their Performance

PNWSCT 2014


Agenda

Agenda

  • Historical Evolution of Anticorrosive Pigments

  • Corrosion

  • Protection

  • Zn free pigments

  • Case Study

  • Accelerated cyclic electrochemical test

  • Analytical experiments

  • Additional systems tested

  • Summary


Historical evolution of anticorrosive pigments

Historical evolution of anticorrosive pigments

Anticorrosive Zn Free Pigments: their performance

Dr. Ricard March, Nubiola


Historical evolution of anticorrosive pigments1

ZINC FREE PIGMENT

Calcium strontium phosphosilicate

Un/Modified with organic surface treatment

Historical evolution of anticorrosive pigments

TRADITIONAL ANTICORROSIVE PIGMENTS

Chromate based pigments

ALTERNATIVE NON CLASSIFIED AS HAZARDOUS ANTICORROSIVE PIGMENTS

ZINC BASED PIGMENTS

  • Zinc Phosphate

  • Modified Zinc Phosphates

Zinc Chromate

Zinc Tetraoxychromate

Strontium Chromate

Barium Chromate

Red lead


Corrosion

Corrosion


Corrosion1

CORROSION

What the corrosion is? Corrosion is a gradual spontaneous process as a result of a chemical reaction with the environment that damages the original metal, typically iron.

+ O2 / + H2O

Spontaneous !!

Non spontaneous !!

Entropy: Order  Disorder


Corrosion process description

Corrosion Process: description

1

Anodic reaction:

Fe  Fe2+ + 2 e-

Cathodic reaction:

O2 + 2 H2O + 4 e- 4 OH-

2

e-

3

O2

Fe2+

H2O

Fe(OH)2

4

delamination

5

blistering

OH-

Protective coating

OH-

OH-

e-

e-

Fe

e-

Metallic substrate (Fe)


Corrosion process reactions

Corrosion Process: reactions

  • Redoxreaction:

    • Anodic reaction (oxidation): Fe  Fe2+ + 2 e-

    • Cathodic reaction (reduction): O2 + 2 H2O + 4 e- 4 OH-

  • Globally:

    • 2 Fe + O2 + 2 H2O + 4 e- 2 Fe2+ + 4 OH- + 4 e-

  • Formation of rust:

    • Fe2+ + 2 OH- Fe(OH)2

    • 4 Fe(OH)2 + O2 4 FeOOH+ 2 H2O

    • 2 FeOOH Fe2O3+ H2O


  • Corrosion process

    Corrosion Process

    • Other compounds can accelerate the reaction:

      • H3O+ (or changes in the pH)

      • SO2 (industrial environment)

      • NaCl (marine environment)

      • Other contaminants: NH4+, SO42-, Mg2+, COO-, etc

      • Also: temperature


    Protection

    protection


    How to slow the corrosion process

    How to Slow the Corrosion Process

    1

    e-flowing

    O2

    Fe2+

    H2O

    delamination

    blistering

    OH-

    Protective coating

    OH-

    OH-

    e-

    e-

    Fe

    e-

    Metallic substrate (Fe)

    It is impossible to interrupt the electron flowing (metal)


    How to slow the corrosion process1

    How to Slow the Corrosion Process

    H2O / O2 in the interface

    2

    O2

    Fe2+

    H2O

    delamination

    blistering

    OH-

    Protective coating

    OH-

    OH-

    e-

    e-

    Fe

    e-

    Metallic substrate (Fe)

    It is possible to reduce water and oxygen flow through barrier effect


    How to slow the corrosion process2

    How to Slow the Corrosion Process

    Cathodic reaction:

    O2 + 2 H2O + 4 e- 4 OH-

    High pH (OH-) displaces the reaction to the left and helps hydroxides precipitation

    Cathodic inhibition by metallic hydroxides and oxides precipitation

    OH- generation in the cathode

    3

    O2

    Fe2+

    H2O

    delamination

    blistering

    OH-

    Protective coating

    OH-

    OH-

    e-

    e-

    Fe

    e-

    Metallic substrate (Fe)


    How to slow the corrosion process3

    How to Slow the Corrosion Process

    Anodic reaction:

    Fe  Fe2+ + 2 e-

    Anodic passivation by metal and iron complexes (phosphates, silicates, …) precipitation

    O2

    Fe2+

    H2O

    Fe2+ generation in the anode

    4

    delamination

    blistering

    OH-

    Protective coating

    OH-

    OH-

    e-

    e-

    Fe

    e-

    Metallic substrate (Fe)


    How to slow the corrosion process4

    How to Slow the Corrosion Process

    Anodic reaction:

    Fe  Fe2+ + 2 e-

    Cathodic reaction:

    O2 + 2 H2O + 4 e- 4 OH-

    Compounds precipitated in the cathode and the anode also avoid the ionic mobility

    O2

    Fe2+

    H2O

    Fe(OH)2

    Ionic mobility

    delamination

    5

    blistering

    OH-

    Protective coating

    OH-

    OH-

    e-

    e-

    Fe

    e-

    Metallic substrate (Fe)


    Z n free pigments

    Zn free pigments


    Zn free pigments

    Zn free pigments

    Calcium Strontium Phosphosilicates: aM*. bP2O5 . cSiO2 . xH2O, for M = Ca, Sr

    • Lowparticlesize

    • Specialparticleshapecombination(acicular + spherical)

      • Elemental particles <1µ forming aggregates and agglomerates up to <10µ

    D(v,0.5)=1.15µ


    Zn free pigments1

    Zn free pigments

    • Higherspecificsurfacearea

    • 21 m2/g vs1 m2/g(std zinc phosphate)

    • Minimizes moisture, oxygen and ionic species diffusion.

    • Microscopical reinforcing action

    • Better adhesion to the metal surface

    • Better dispersion capability

    • More active surface (allows lower pigment dosage)

    • Better performance in thin film systems

    • Low effect on gloss


    Zn free pigments calcium strontium phosphosilicates

    Zn free pigments: Calcium Strontium Phosphosilicates

    O2 + 2 H2O + 4 e- 4 OH-

    Cathodic reaction displacement

    Barrier effect

    SEM (scanning electron microscopy) 10000X

    Cathodic inhibition: Ca/Sr hydroxides

    aM*.bP2O5.cSiO2.xH2O

    M= Ca, Sr

    Anodic passivation: Ca/Sr/Fe phosphates&silicates complexes

    Metallic substrate (Fe)


    Case study

    case study


    Anticorrosive zn free pigments their performance

    DOE

    • WB Styrene Acrylic

    • Substrate: CRS, S-46

    • 60 - 90 

    • 240 - 1170 h Neutral Salt Spray ASTM B117

    • Formulated at same:

      • Anticorrosive Pigment Volume Content (3% - 6%)

      • PVC/CPVC ratio (same free binder volume, 0,47)

    • DOE: Full factorial experiment 24(16 runs of 1 replica in one block):

      • Pigment (qualitative): zinc phosphate – zinc free

      • Dose (quantitative): 3% - 6%

      • Thickness (quantitative): 60  - 90 

      • Exposure time (quantitative): 240 h – 1170 h

    • Exit parameters:

      • Oxidation at scribe

      • Oxidation on the panel

      • Adhesion at the scribe


    Panel evaluation

    Panel Evaluation

    BlisteringISO 4628-2

    “Cross cut” adhesionASTM D3359

    Adhesion at thescribeASTM D1654 B

    Oxidation at thescribeASTM D1654 A

    Oxidationonthe panel ASTM D610


    Doe pareto plots

    DOE: ParetoPlots

    Exposure time

    Exposure time

    Thickness

    PIGMENT

    Dose

    Exposure time


    Doe interaction plot for oxidation at scribe

    DOE: interaction plot for oxidation at scribe


    Doe interaction plot for oxidation on the panel

    DOE: interaction plot for oxidation on the panel


    Faster activity and higher efficiency of zn free

    Faster activity and higher efficiency of Zn free

    Zn free

    3%

    60 

    240 h

    Zn phosphate

    6%

    60 

    240 h

    Zn free

    6%

    90 

    1170 h

    Zn phosphate

    6%

    90 

    1170 h


    Anticorrosive zn free pigments their performance

    acet


    Acet the need

    ACET: The need

    Accelerated Cyclic Electrochemical Technique (ACET)

    24 h

    100 - 10.000 h

    4.400 – 25.000 h

    UNE 48315-1

    ASTM B117


    Acet steps

    ACET: Steps


    Acet information

    ACET: Information


    Acet equivalent circuit

    ACET: Equivalent circuit

    Equivalent circuit used to model EIS & ACET

    Coating properties

    Interface


    Panel evaluation standard ssc

    Panel Evaluation: Standard (SSC)

    BlisteringISO 4628-2

    “Cross cut” adhesionASTM D3359

    Adhesion at thescribeASTM D1654 B

    Oxidation at thescribeASTM D1654 A

    Oxidationonthe panel ASTM D610


    Panel evaluation acet

    Panel Evaluation: ACET

    Impedancevalues:

    Emax, Emin, ∆E and Bode graph

    Equivalentcircuitparameters:

    Rp and Cdl

    Impedancevalues:

    |Z|max, |Z|min and ∆Z

    Equivalentcircuitparameters:

    Rpo and Cc


    Acet ann

    ACET: ANN

    Use of this methodology in the industry?

    Electrochemical Models?

    Artificial Neural Networks (ANN)


    Acet correlation

    ACET: correlation


    Analytical experiments

    analytical experiments


    Sem panel observation

    SEM: panel observation


    Sem mapping

    SEM: mapping


    Sem cross section observation

    SEM: cross-sectionobservation

    Blank

    Zn Phosphate

    Zn free

    • Water Based Styrene Acrylic

    • Substrate: CRS, S-46

    • 70 

    • 450 h Neutral Salt Spray ASTM B117

    • Formulated at same:

      • Anticorrosive Pigment Volume Content (6%)

      • PVC/CPVC ratio (same free binder volume)


    Sem cross section observation1

    SEM: cross-sectionobservation

    Blank

    Zinc phosphate

    Zn free

    Oxidation

    The finest particle distribution


    Sem cross section observation2

    SEM: cross-sectionobservation

    Zinc phosphate: Energy Distribution Spectroscopy Element Mapping (EDS element mapping)

    Fe

    O

    Coating

    Zn

    P

    Si

    Panel


    Sem cross section observation3

    SEM: cross-sectionobservation

    Zinc free pigment: Energy Distribution Spectroscopy Element Mapping (EDS element mapping)

    Fe

    O

    Coating

    Panel

    Sr

    Ca

    P

    Si

    Smaller particle size allows the pigment to have a more direct interaction with the metal surface.


    Sem cross section observation4

    SEM: cross-sectionobservation

    Energy Distribution Spectroscopy Linescan (EDS Linescan)

    Zn free (line 2)

    Blank

    Zn free (line 1)

    Panel

    Coating

    Panel

    Coating

    Panel

    Coating


    Sem cross section observation5

    SEM: cross-sectionobservation

    Energy Distribution Spectroscopy Linescan (EDS Linescan)

    Blank

    Panel

    Coating


    Sem cross section observation6

    SEM: cross-sectionobservation

    Energy Distribution Spectroscopy Linescan (EDS Linescan)

    Zn free (line 1)

    Panel

    Coating


    Sem cross section observation7

    SEM: cross-sectionobservation

    Energy Distribution Spectroscopy Linescan (EDS Linescan)

    Zn free (line 2)

    Panel

    Coating


    Additional systems tested

    additional systems tested


    Sb wash primer

    SB Wash Primer

    Zinc free

    Zinc Tetraoxychromate

    • 2K Etch/Wash primer: polyvinyl butyral epoxy modified

    • Substrate: Galvanized Panels, SG015

    • 20  (lower half – only primer)

    • 50  (upper half – primer & intermediate)

    • 300 h Neutral Salt Spray ASTM B117

    • Formulated at same:

      • Anticorrosive Pigment Volume Content (9%)

      • PVC/CPVC ratio (same free binder volume)


    Sb wash primer1

    SB Wash Primer

    Cross cut test (ASTM D3359)

    Aluminum

    3105H14 AA015D (Espancolor)

    Mild steel

    SB015D (Espancolor)

    Galvanized steel

    SG015 (Espancolor)

    Cold rolled steel

    S-46 (Q-Panel)

    Zinc Tetraoxychromate

    5B

    5B

    4B

    5B

    Zinc free

    5B

    5B

    3B

    4B


    Sb alkyd

    SB Alkyd

    6% Zinc Phosphate

    6% Zinc free

    Blank

    • Solvent Based Alkyd

    • Substrate: CRS, S-46

    • 60 

    • 641 h Neutral Salt Spray ASTM B117

    • Formulated at same:

      • Anticorrosive Pigment Volume Content (6%)

      • PVC/CPVC ratio (same free binder volume)


    Sb alkyd1

    SB Alkyd

    Blank

    6% Zinc Phosphate

    3% Zinc free

    6% Zinc free

    Zn free pigment shows better performance, even at lower dosage.


    Sb epoxy

    SB Epoxy

    Blank

    6% Zinc Phosphate

    6% Zinc free

    • Solvent Based Epoxy

    • Substrate: CRS, S-46

    • 60 

    • 1100 h Neutral Salt Spray ASTM B117

    • Formulated at same:

      • Anticorrosive Pigment Volume Content (6%)

      • PVC/CPVC ratio (same free binder volume)


    Sb epoxy1

    SB Epoxy

    Blank

    10 % Zinc Phosphate

    6% Zinc free

    1100 h

    Zn free pigment shows better performance, even at lower dosage.

    Blank

    10 % Zinc Phosphate

    8% Zinc free

    1320 h


    Sb 2k polyurethane

    SB 2K Polyurethane

    Blank

    6% Zinc Phosphate

    6% Zinc free

    • Solvent Based 2K Polyurethane (acryl/polyisocyanate)

    • Substrate: CRS, S-46

    • 60 

    • 385 h Neutral Salt Spray ASTM B117

    • Formulated at same:

      • Anticorrosive Pigment Volume Content (6%)

      • PVC/CPVC ratio (same free binder volume)


    Sb 2k polyurethane pot life

    SB 2K Polyurethane: pot-life

    No effect on pot life / shelf life


    Powder coating

    Powdercoating

    • Powder Coating, Epoxy-Polyester

    • Substrate: Phosphated steel, Bonderite 1000

    • 90 

    • 1000 h Neutral Salt Spray ASTM B117

    • Formulated at same:

      • Anticorrosive Pigment Volume Content (2,3%)

      • PVC/CPVC ratio (same free binder volume)

    • Powder Coating, Epoxy-Polyester

    • Substrate: Aluminium, 3105H14

    • 90 

    • 4000 h Neutral Salt Spray ASTM B117

    • Formulated at same:

      • Anticorrosive Pigment Volume Content (2,3%)

      • PVC/CPVC ratio (same free binder volume)

    Zinc free

    Blank

    Zinc free

    Blank


    Wb acrylic dtm

    WB Acrylic DTM

    Blank

    4,5% Zinc Phosphate

    4,5% Zinc free

    Gloss 85º = 69

    Gloss 85º = 57

    Gloss 85º = 71

    • WB Acrylic DTM

    • Substrate: CRS, S-46

    • 90 

    • 310 h Neutral Salt Spray ASTM B117

    • Formulated at same:

      • Anticorrosive Pigment Volume Content (4,5%)

      • PVC/CPVC ratio (same free binder volume)

    Zinc free:

    • No gloss reduction

    • Good anticorrosive activity


    Wb alkyd

    WB Alkyd

    Blank

    4,5% Zinc Phosphate

    4,5% Zinc free

    • WB Alkyd

    • Substrate: CRS, S-46

    • 90 

    • 500 h Neutral Salt Spray ASTM B117

    • Formulated at same:

      • Anticorrosive Pigment Volume Content (4,5%)

      • PVC/CPVC ratio (same free binder volume)


    Wb styrene acrylic

    WB StyreneAcrylic

    6% Calcium phosphate

    6% Zinc phosphate

    6% Zinc free

    Blank

    • WB Styrene Acrylic

    • Substrate: CRS, S-46

    • 55 

    • 478 h Neutral Salt Spray ASTM B117

    • Formulated at same:

      • Anticorrosive Pigment Volume Content (6%)

      • PVC/CPVC ratio (same free binder volume)


    Summary

    summary


    Summary1

    Summary

    • Zinc free pigments are an effective environmentally friendly option to zinc phosphate based products.

    • Compared to anticorrosive zinc phosphate based products, they show

      • an adhesion improvement on cold rolled steel.

      • a lower effect on gloss.

      • a lower reactivity in WB and SB polyurethane systems.

    • Accelerated evaluation have been used and correlated with results obtained in classic evaluation methods like Salt Spray test.

    • All these macroscopic facts are related to the chemical composition and physical properties of the pigment.

    • Proper adjustment of paint formula variables is a complex procedure. The expertise and skill of a reputable paint company and their staff of paint chemists is invaluable for the long term performance of a coating system


    Anticorrosive zn free pigments their performance

    Thank you for your attention


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