PSI - Issue 10

A. Karanika et al. / Procedia Structural Integrity 10 (2018) 66–72 A. Karanika et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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3.4. AC131 SolGel samples

Al surfaces treated with the AC131 SolGel were tested for corrosion protection as per ASTM B117 specification. The surfaces failed after 30 h in the SST, indicating that AC131 alone cannot provide corrosion protection, and may not replace Alodine 1200 (48 h in SST) as chemical conversion coating. Al surfaces treated with AC131 SolGel and then primed with conventional water-based epoxy primer and then top-coated with a water-soluble topcoat F70-A were passed successfully the corrosion protection test as per ASTM B117, Fig.7. After 2000 h in SST, no pits were observed in both the primed and the top-coated coupons.

(a)

(b)

(c)

Fig. 7. Al-Li samples treated with (a) SolGel, (b) SolGel and Primer and (c) SolGel, Primer and TopCoat. Cr-free solutions were used.

4. Conclusions

The research is on progress on both conventional and new alloys and surface treatments with encouraging technical results, in terms of mechanical properties and formability, while surface treatments are close to meet the technical specifications set for the current technologies. For the case of the TFSAA the research is on-progress, while for the Sol-Gel treated the painted samples successfully passed the corrosion testing.

Acknowledgements

This research at Hellenic Aerospace Industry S.A. was performed in cooperation with TEI of Sterea Ellada in the framework of the JTI-CS2-AIR ecoTECH core project, funded by the Clean Sky Joint Technology Initiative.

References

Dursun, T., Soutis, C. 2014. Recent developments in advanced aircraft aluminium alloys. Materials & Design 56, 862-871. Polmear, I., StJohn, D., Nie, J.F., Qian, M., 2017. Light alloys: metallurgy of the light metals. Butterworth-Heinemann., ISBN: 9780080994307 ASTM B117, Standard Practice for Operating Salt Spray (Fog) Apparatus Twite, R.L., Bierwagen, G.P., 1998. Review of alternatives to chromate for corrosion protection of aluminum aerospace alloys. Progress in organic coatings, Department of Polymers and Coatings, NDSU, Fargo, ND 58105, USA 33(2), 91-100.