Protection of Magnesium Alloys as Lightweight Materials for … · 2018-11-17 · Mg Alloys in the...

Protection of Magnesium Alloys as Lightweight Materials for Applications

in the Aerospace Industry

Lénia M. Calado1, Maryna Taryba1, Maria J. Carmezim1,2, M. Fátima Montemor1

1CQE, DEQ, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal2ESTSetúbal, Instituto Politécnico de Setúbal, Setúbal, Portugal

International Workshop for Global Sustainability – PGS Workshop 2018

1

Summary

Magnesium alloys in the aerospace industry

Corrosion susceptibility of magnesium alloys

Protection strategies

Outline of experimental work and experimental details

Characterization of develped coating (morphology and anticorrosive performance)

Conclusions

Ongoing and future work

L. Calado et al., 2018

• Alternative fuels

• Engines with less fuel consumption

• Lightweight materials for aircraft

weight reduction

Regulations for reduction of

greenhouse gas emissions

• Lighter than other structural metals

• Good mechanical properties

• Castability

• Nontoxic

• Recyclable

High strength-to-weight ratio

Aeronautic Industry

2

Mg Alloys in the Aerospace Industry

Density near R. T. (g/cm3)

Magnesium 1.70 – 1.85

Aluminum > 2.70

Steel > 7.70


3

Mg Alloys in the Aerospace Industry

• Cockpit instrument panel3

• Seat components3

• Service door inner panel3

• Graphite/magnesium truss structures4

• Chassis for planetary probes (Mariner

2, MESSENGER power distribution

unit)5,6

AZ92

Boeing 747 thrust

reverser1

1A. Luo. Journal of Magnesium and Alloys, vol. 1, no. 1, pp. 2-22, 2013 / www.airteamimages.com2A. Luo. Journal of Magnesium and Alloys, vol. 1, no. 1, pp. 2-22, 2013 / www.jetevolutions.com3A. Dziubińska et al. Advances in Science and Technology Research J, vol. 10, no. 31, pp. 158-168, 20164S.Rawal. Acta Astronautica, vol. 146, pp. 151-160, 20185abyss.uoregon.edu6E. Schaefer et al. Johns Hopkings APL Technical Digest, vol. 28, no. 1, 2008

ZE41

Bombardier Learjet

60 turbofan (Pratt &

Whitney Canada)2


4

Very reactive material

Surface film that is formed when magnesium is exposed to air is poorly protectiveand less stable than films formed on other materials (aluminum, stainless steels)

𝑴𝒈+ 𝟐𝑯𝟐𝑶 → 𝑴𝒈(𝑶𝑯)𝟐 +𝑯𝟐

𝑀𝑔 → 𝑀𝑔2+ + 2𝑒−

2𝐻2𝑂 + 2𝑒− → 2𝑂𝐻− +𝐻2

𝑀𝑔 → 𝑀𝑔+ + 𝑒−

𝑀𝑔+ + 𝐻2𝑂 → 𝑀𝑔2+ + 𝑂𝐻− +1

2𝐻2

Corrosion Susceptibility of Mg AlloysL. Calado et al., 2018

5

Protection Strategies

Source: D. Landolt. Corrosion and surface chemistry of metals. 2nd ed. Lausanne: CRC Press, 2007

Appropriate

design

Selection and

combination of

materials

Protective

coatingsInhibitors

Electrochemical

protection


6


Sources: M. F. Montemor. Functional and smart coatings for corrosion protection: a review of recent advances. Surf. Coatings Technol. vol. 258, pp. 17-37, 2014

J. E. Gray, B. Luan. Protective coatings on magnesium and its alloys – a critical review. J. Alloys Compd. vol. 336, pp. 88-113, 2002

C. Blawert, W. Dietzel, E. Ghali, G. Song. Anodizing treatments for magnesium alloys and their effect on corrosion resistance in various environments. Adv. Eng. Mater. vol. 8, pp. 511-533, 2006

Physical barrier

Protection from external

aggressive environment

High adhesion

Mechanical resistance

Flexibility

Protective

coatingsInhibitors


7


Sources: M. F. Montemor. Functional and smart coatings for corrosion protection: a review of recent advances. Surf. Coatings Technol. vol. 258, pp. 17-37, 2014

J. E. Gray, B. Luan. Protective coatings on magnesium and its alloys – a critical review. J. Alloys Compd. vol. 336, pp. 88-113, 2002

C. Blawert, W. Dietzel, E. Ghali, G. Song. Anodizing treatments for magnesium alloys and their effect on corrosion resistance in various environments. Adv. Eng. Mater. vol. 8, pp. 511-533, 2006

Physical barrier

Protection from external

aggressive environment

High adhesion

Mechanical resistance

Flexibility

Protective

coatingsInhibitors

Extend protective

ability and lifetime

Self-healing coatings

Improved and

autonomous protection


8

Outline of Experimental Work

Epoxy-Silane

Network structure with good adhesion to metallic substrate

Epoxy

Cross-linked, dense barrier

Silane

Linkage between metallic substrate

and organic matrix

Characterization of formulated coatings

Evaluation of protective performance

Modification of epoxy-silane reference coating with CeO2 nanoparticles


9

Outline of Experimental Work

Sample Pre-treatment

Mechanical polishing with SiC paper

HF treatment

Application of Coating

Mixture of components

Dip-coating

Curing


10

Uniform coating

thickness

FEG-SEM image of the cross-section of the modified coating applied on AZ31.

Coating Morphology

Coating Thickness (µm)

Reference 325 ppm CeO2

9.9 ± 1.3 10.4 ± 1.9

Uniform coating

surface


11

10-2 10-1 100 101 102 103 104103

104

105

106

107

108

109

1010

1011

Frequency (Hz)

|Z|

(oh

m.c

m²)

4h1 day4 days7 days8 days14 days15 days21 days22 days29 daysBase-coating, 29 days

10-2 10-1 100 101 102 103 104

-90

-65

-40

-15

Frequency (Hz)

Ph

ase

An

gle

(º)

4h1 day4 days7 days8 days14 days15 days21 days22 days29 daysBase-coating, 29 days

Bode plots of coated AZ31 during immersion in 0.05 M NaCl. Results obtained after 29 days of immersion for the

reference coating are shown for comparison.

Electrochemical Impedance SpectroscopyL. Calado et al., 2018

12

0 5 10 15 20 25 301E7

1E8

1E9

1E10

1E11

1E12

|Z| (

cm

2)

Immersion Time (days)

Base-coating

325 ppm CeO2

Evolution of low frequency impedance modulus (0.01 Hz) with immersion time in 0.05 M

NaCl for AZ31 coated with blank coating and with modified coating.


13

0 5 10 15 20 25 3010

8

109

1010

1011

1012

R (c

m2)

Time of immersion (days)

Rcoat. pores

Rint

0 5 10 15 20 25 3010

7

108

109

1010

R (c

m2)


Rcoat. pores

Rint

Evolution of resistances for blank and modified coating during immersion testing in 0.05 M NaCl.

Reference Coating Modified Coating

0 5 10 15 20 25 3010

7

108

109

1010

R (c

m2)


Rcoat. pores

Rint

0 5 10 15 20 25 3010

7

108

109

1010

R (c

m2)


Rcoat. pores

Rint

Rint

Rcoat

R1 CPE1

R2 CPE2

R3

Element Freedom Value Error Error %

R1 Free(±) 1090 792.91 72.744

CPE1-T Free(+) 4.3493E-10 2.5728E-12 0.59154

CPE1-P Free(+) 0.98211 0.00081983 0.083476

R2 Free(+) 3.5986E09 1.398E09 38.848

CPE2-T Free(+) 3.7647E-11 1.8122E-12 4.8137

CPE2-P Free(+) 0.66317 0.021213 3.1987

R3 Free(+) 1.4031E11 8.777E09 6.2554

Chi-Squared: 0.0005241

Weighted Sum of Squares: 0.035114

Data File: C:\Users\Lénia\Desktop\IST\Lab Work\EIS\

CeO2 set 4\4B1_4h_b.dta

Circuit Model File: C:\Users\Lénia\Desktop\IST\Lab Work\EIS\

@BRANCO\Modelo_2ccotempo.mdl

Mode: Run Fitting / Selected Points (3 - 39)

Maximum Iterations: 100

Optimization Iterations: 0

Type of Fitting: Complex

Type of Weighting: Calc-Modulus

Electrolyte

ResistanceCoating

Interfacial

processes


Rint

Rcoat

14

LEIS

LEIS admittance mapping over an artificial defect on the surface of the reference coating after 0.5 h, 24 h, and 49.5 h immersion in 0.005 M NaCl.

Reference Coating

Localized Electrochemical Impedance Spectroscopy


15

LEIS

325 ppm CeO2

LEIS admittance mapping over an artificial defect on the surface of the ceria-modified coating after 0.5 h, 24 h, and 49.5 h immersion in 0.005 M NaCl.



16

LEIS

Optical microscope images of artificial defects made on

the reference and modified coatings

Ratio between the measured admittances during LEIS and the

first registered admittance for each sample during immersion

in 0.005 M NaCl.



17

SVET

SVET analysis of artificial defect (200 µm) in base-coating. Immersion in 0.05 M NaCl.

ReferenceVery active defect during the whole immersion time

Strong cathodic activity – Hydrogen release

µA/cm21 h

µA/cm220 h1 h

Scanning Vibrating Electrode Technique


18

SVET

Scanning Vibrating Electrode Technique

SVET analysis of artificial defect (200 µm) in modified coating. Immersion in 0.05 M NaCl.

CeO2

First signs of activity after 20 h of immersion

Cathodic activity is 2 orders of magnitude lower than for reference coating

1 h

µA/cm2 µA/cm2

1 h 22 h


19

Conclusions

Delay in onset of corrosion

Healing effect of CeO2 nanoparticles for epoxy-silane coating

Improvement in anticorrosive performance by incorporation of small amount of ceria

nanoparticles

Highly protective coating with stable anticorrosion performance up to 29 days of

immersion in 0.05 M NaCl

No coating delamination when substrate is exposed to 0.005 M NaCl electrolyte


Cathodic and anodic activity are kept low at artificial defect up to 22 h of immersion

in 0.05 M NaCl. First signs of activity detected only after 20 h of immersion

20

Ongoing and Future Work

pH sensitive corrosion inhibitor

Synergistic effect of corrosion inhibitor mixture

Structural magnesium alloy

Mechanical properties


21

Acknowledgements

UID/QUI/00100/2013


22

Thank you for your attention

Protection of Magnesium Alloys as Lightweight Materials for Applications

in the Aerospace Industry

Lénia M. Calado1*, Maryna Taryba1, Maria J. Carmezim1,2, M. Fátima Montemor1

1CQE, DEQ, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal2ESTSetúbal, Instituto Politécnico de Setúbal, Setúbal, Portugal

*[email protected]

International Workshop for Global Sustainability – PGS Workshop 2018

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