K3-en / PhysChemLabCorrConvCoatingsRight

Research programme

• Corrosion protection

• Heterogeneous catalysis

• Implementation of computer graphics

Corrosion protection

In the field of corrosion protection our research is focused on the following topics:

• Corrosion inhibitors

• Conversion coatings

• Sol-gel coatings

• Superhydrophobic, self-cleaning and anti-icing coatings

• Atomic layer deposition (ALD) coatings

• Antifouling coatings

• Materials and coatings for biomedical applications

Conversion coatings

Conversion coatings can be defined as coatings formed by conversion from soluble salt to a slightly soluble or insoluble oxide and/or hydroxide which precipitates either throughout the metal surface, or at intermetallic particles which are electrochemically more noble in respect to surrounding matrix and where oxygen reduction takes place. Inhibitory action of these conversion coatings is based on the retardation of cathode reaction (i.e. oxygen evolution) on corroding surfaces. Today three main types of conversion coatings are being explored on aluminium alloys: rare earth coatings, zirconium and/or titanium coatings and trivalent chromium coatings:

• Rare earth compounds (mainly Ce and La) are environmentally friendly, exhibit low toxicity and are available in natural sources at a reasonable price.
  

• Zirconium- and titanium-based oxides prepared from conversion bath containing hexafluoro zirconic or hexafluoro titanic acid
  

• Trivalent chromium process coating, totally free of Cr(VI) generally contains zirconium hexafluoride and small amount (≤5 wt%) of trivalent chromium salt.
  

Figure: (a) Polarization curves recorded for aluminium alloy AA7075-T6 in 0.1 M NaCl solution with and without added 3 mM cerium(III) nitrate, chloride and acetate salts. Corrosion potential (E_corr), pitting potential (E_pit) and the span of passivity region (∆E) are denoted. dE/dt=1 mV/s. (b) Confocal microscope images of artificially made scratch on AA7075-T6 after 72 h immersion in 0.1 M NaCl and 0.1 M NaCl with added 3 mM CeCl₃ and 3 mM Ce(Ac)₃. (Reprinted from the publication by I. Milošev, P. Rodič, Corrosion, 2016, 72, 1021–1034)

Conversion coatings: selected publications

1. I. Milošev, P. Rodič, J. Electrochem. Soc., 2022, 169, 011504-1–011504-17.

2. I. Milošev, B. Kapun, P. Rodič, J. Electrochem. Soc., 2022, 169, 91501-1–091501-21.

3. P. Rodič, I. Milošev, Studia UBB Chemia, 2020, LXV, 227–244.

4. G. Šekularac, I. Milošev, J. Electrochem. Soc.,2020, 167, 021509

5. G. Šekularac, J. Kovač, I. Milošev, Corros. Sci.,2020, 169, 1086151

6. B. Volarič, A. Manzare, S. Virtanen, I. Milošev, Corrosion, 2020,76, 18–38

7. P. Rodič, I. Milošev, M. Lekka, F. Andreatta, L. Fedrizzi, Electrochim. Acta, 2019, 308, 337–349.

8. P. Rodič, I. Milošev, Corros. Sci., 2019, 149, 108–122.

9. M. Mujdrica Kim, B. Kapun, U. Tiringer, G. Šekularac, I. Milošev, Coatings, 2019, 9, 563

10. I. Milošev, G.S. Frankel, J. Electrochem. Soc., 2018, 165, C1–C18.

11. I. Milošev, B. Volarič, Corrosion, 2017, 73, 822–843.

12. B. Volarič, I. Milošev, Corr. Eng. Sci. Technol., 2017, 52, 201–211.

13. P. Rodič, I. Milošev, J. Electrochem. Soc., 2016, 163, C85–C93.

14. I. Milošev, P. Rodič, Corrosion, 2016, 72, 1021–1034.

Projects related to conversion coatings

• ARRS project Lightweight alloys based on aluminium as materials with increasing potential in transport industry, project leader: dr. Ingrid Milošev, 2014–2017

• KET4CP Microgrant Proposal Advanced environmentally friendly surface treatment for aluminium and its alloys used in aircraft industry together with FerroČrtalič, Slovenia and Joanneum Research Forschungsgesellschaft mbH-JR, Austria), project leader: dr. Ingrid Milošev, duration: 15. 1. 2020 – 15.6.2020

• Bilateral project Slovenia-USA Corrosion protection of technologically important materials using environmentally friendly coatings, project leaders: dr. I. Milošev and dr. G. S. Frankel, 2015–2016