CORROSION PROTECTION FOR METALLIC SUBSTRATES

Abstract

A composition suitable for coating a metallic substrate that is susceptible to corrosion is disclosed. The composition comprises a carrier medium, 2D material/graphitic platelets, and one or both of conductive carbon black particles and carbon nanotubes, in which the 2D material/graphitic platelets comprise nanoplates of one or more 2D materials and or nanoplates of one or more layered 2D materials and or graphite flakes in which the graphite flakes have one nanoscale dimension and 25 or less layers, the conductive carbon black particles have a mean particle size in the range of 1 nm to 1000 nm, and the carbon nanotubes are single or multiwalled.

Claims

1. A composition suitable for coating a metallic substrate that is susceptible to corrosion characterised in that the composition comprises a carrier medium, 2D material/graphitic platelets, and one or both of conductive carbon black particles and carbon nanotubes, in which the 2D material/graphitic platelets comprise nanoplates of one or more 2D materials and or nanoplates of one or more layered 2D materials and or graphite flakes in which the graphite flakes have one nanoscale dimension and 25 or less layers, the conductive carbon black particles have a mean particle size in the range of 1 nm to 1000 nm, and the carbon nanotubes are single or multiwalled.

2. A composition according to claim 1 in which the 2D material/graphitic platelets are comprised of one or more of graphene, graphyne, phosphorene, borophene, a 2D in-plane heterostructure of two or more of graphene graphyne phosphorene and or borophene, layered graphene, layered graphyne, layered phosphorene, layered borophene, a 2D vertical heterostructure of two or more of graphene graphyne phosphorene and or borophene, and or graphite flakes in which the graphite flakes have one nanoscale dimension and 25 or less layers.

3. A composition according to claim 1 or 2 in which the 2D material/graphitic platelets and conductive carbon black particles and or carbon nanotubes in combination comprise between 0.002 wt % and 0.09 wt % of the composition, between 0.002 wt % and 0.004 wt % of the composition, between 0.0026 wt % and 0.04 wt % of the composition, between 0.0026 wt % and 0.0035 wt % of the composition, between 0.006 wt % and 0.009 wt % of the composition, around 0.003 wt % of the composition, or around 0.03 wt % of the composition

4. A composition according to claim 1 or 2 in which the 2D material/graphitic platelets comprise between 0.002 wt % and 0.09 wt % of the composition, between 0.002 wt % and 0.004 wt % of the composition, between 0.0026 wt % and 0.04 wt % of the composition, between 0.0026 wt % and 0.0035 wt % of the composition, between 0.006 wt % and 0.009 wt % of the composition, around 0.003 wt % of the composition, or around 0.03 wt % of the composition.

5. A composition according to any of claims 1 to 4 in which the ratio of the weight of the 2D material/graphitic platelets to the total weight of the 2D material/graphitic platelets and conductive carbon black particles and or carbon nanotubes is 50%, 60%, 70%, 80%, 20%, 30%, 40%, between 50 and 60%, between 50 and 70%, between 50 and 80%, between 20 and 50%, between 30 and 50%, between 40 and 50%, between 20 and 80%, between 30 and 70%, or between 40 and 60%.

6. A composition according to any of claims 1 to 5 in which at least 50% of the 2D material/graphitic platelets and conductive carbon black particles and or carbon nanotubes are not in physical and or electrical contact with any other 2D material/graphitic platelets and conductive carbon black particles and or carbon nanotubes.

7. A composition according to any of claims 1 to 6 in which at least one of the 2D material/graphitic platelets and conductive carbon black particles and or carbon nanotubes have a particle size distribution with a D50 of less than 30 m, less than 20 m, or less than 15 m.

8. A composition according to any of claims 1 to 7 in which the 2D material/graphitic platelets are comprised of one or more of graphene, layered graphene, and or graphite flakes in which the graphite flakes have one nanoscale dimension and 25 or less layers, and in which at least 50% of the graphene, layered graphene, and or graphite flakes have an electrical conductivity greater than around 2.1510.sup.7 S/m at 20 C. or greater than around 3.510.sup.7 S/m at 20 C.

9. A composition according to any of claims 1 to 8 in which at least 50% of the conductive carbon black particles have an electrical conductivity greater than around 1.010.sup.4 S/m at 20 C.

10. A composition according to any of claims 1 to 8 in which at least 50% of the carbon nanotubes have an electrical conductivity greater than around 1.0010.sup.6 S/m at 20 C.

11. A composition according to any of claims 1 to 10 in which at least 50 wt % of the 2D material/graphitic platelets are comprised of graphite flakes with nanoscale dimensions and 25 or less layers.

12. A composition according to any of claims 1 to 11 in which the carrier medium is electrically non-conductive.

13. A composition according to any of claims 1 to 12 in which the carrier medium is selected from crosslinkable resins, non-crosslinkable resins, thermosetting acrylics, aminoplasts, urethanes, carbamates, polyesters, epoxies, silicones, polyureas, silicates, polydimethyl siloxanes, and mixtures and combinations thereof.

14. A composition according to any of claims 1 to 13 in which the carrier medium is plastically deformable once it has set/cured

15. A composition according to any of claims 1 to 14 in which the composition further comprises a solvent.

16. A composition according to any of claims 1 to 15 in which the composition further comprises a dispersant.

17. A coating system for a metallic substrate that is susceptible to corrosion for creation of a first coating on the metallic substrate, and, subsequently, a second coating over the first coating characterised in that the first coating comprises a composition according to any of claims 1 to 16, and the second coating is formed from a second composition which comprises a carrier medium and 2D material/graphitic platelets in which the 2D material/graphitic platelets comprise more than 0.1 wt % of the second composition.

18. A coating system according to claim 17 in which the 2D material/graphitic platelets of the second composition one of or a mixture of two or more of graphene, graphene oxide, reduced graphene oxide nanoplates, hexagonal boron nitride, molybdenum disulphide, tungsten diselenide, silicene, germanene, Graphyne, borophene, phosphorene, a 2D in-plane heterostructure of two or more of graphene, graphene oxide, reduced graphene oxide nanoplates, hexagonal boron nitride, molybdenum disulphide, tungsten diselenide, silicene, germanene, Graphyne, borophene, phosphorene, bilayer graphene, bilayer graphene oxide, bilayer reduced graphene oxide nanoplatelets, few-layer graphene, few-layer graphene oxide, few-layer reduced graphene oxide nanoplatelets, graphite flakes in which the graphite flakes have one nanoscale dimension and 25 or less layers, layered hexagonal boron nitride (hBN), molybdenum disulphide (MoS.sub.2), tungsten diselenide (WSe.sub.2), silicene (Si), germanene (Ge), Graphyne (C), borophene (B), phosphorene (P), and or a 2D vertical heterostructure of two or more of the aforesaid materials.

19. A coating system according to claim 17 or 18 in which the 2D material/graphitic platelets of the second composition comprise between 0.1 wt % and 20 wt % of the composition, between 0.1 wt % and 6.0 wt % of the composition, or between 0.1 wt % and 0.5 wt % of the composition.

20. A coating system according to any of claims 17 to 19 in which more than 50% of the 2D material/graphitic platelets of the second composition have an electrical conductivity which is less than the electrical conductivity of more than 50% of the graphene platelets of the first composition.

21. A coating system according to any of claims 17 to 20 in which more than 50% of the 2D material/graphitic platelets of the second composition have an electrical conductivity of around or less than 2.010.sup.5 S/m at 20 C.

22. A method of treatment of a metallic substrate in which the substrate is coated with a composition according to any of claims 1 to 16.

23. A method of treatment of a metallic substrate in which the substrate is treated with the system according to any of claims 17 to 21.

24. A method of treatment according to claim 22 or 23 in which the substrate is aluminium, an aluminium alloy, or a magnesium based alloy.

Description

EXAMPLE DATA

[0073] The data in Tables 3a and 3b demonstrates the electrochemical values obtained for samples which have scribe damage, and intact coatings. It shows the corrosion potential (E.sub.corr) The anodic and cathodic currents, and corrosion rate in m per year and mils per year. This data is used to construct Tafel plots which in themselves demonstrate whether the corrosion mechanism is by barrier, or passivation.

[0074] For the hybrid samples, including carbon black particles, single wall carbon nanotubes and graphene Grade 1, and blends thereof, the coatings were not studied in an unscribed state since no effect on the corrosion of the substrate was observed with fully intact coatings. This is due to the fact that corrosive species such as water, ions or oxygen are prevented from interacting with the substrate.

[0075] The Tafel plot showing passivation occurring with Formulations 2 and 10 when scribed is shown in Table 4. The plots are labelled with the formulation number.

[0076] The near flat gradient of the upper curve in Table 4 is consistent with passivation occurring at the substrate in this case an aluminium alloy. When no scribe is present, the coating itself acts as a barrier, and no passivation occurs as water and oxygen are not present at the substrate. The Tafel plot showing no passivation occurring with Formulation 2 when unscribed is shown in Table 5

[0077] In contrast an indication of barrier performance can be seen from Formulation 5. The Tafel plot occurring with Formulation 5 when scribed and unscribed are shown in Tables 6 and 7 respectively. There is little difference in the anodic and cathodic currents shown which is an indication that Graphene Grade 2 performs as a physical barrier, rather than controlling corrosion by passivation.

[0078] Barrier performance of the Graphene Grade 2 is also demonstrated with water vapour transmission testing. With five Formulations and a Control C as per Table 8.

[0079] The epoxy was cured with a polyamide blend (epoxy:polyamide 5.36:1), and the panels were allowed to cure for a period of at least 7 days at a consistent ambient temperature.

[0080] Testing for the transmission of water through the film showed the results in Table 9.

[0081] As may be seen, the data in Table 9 demonstrates a significant decrease in the transmission of water through the film as the loading of the Graphene Grade 2 increases.