MARINE COATING COMPOSITION

Abstract

The invention relates to an anti-corrosion and anti-fouling composition, particularly to a protective composition for a marine body, wherein in said composition comprises a copper alloy of the form Cu(M*), wherein M* is at least one metal which is more electronegative than copper, wherein said composition comprises ceramic filler particles in the range of from 0.1 to 20 wt %.

Claims

1. A protective composition for a marine body, wherein said composition comprises a copper alloy of the form Cu(M*), wherein M* is at least one metal, which is more electronegative than copper, wherein said composition comprises reinforced filler particles in the range of from 0.1 wt % to 20 wt %.

2. The composition according to claim 1, wherein M* is at least one of tin, zinc, iron, cadmium, aluminium, beryllium, or magnesium, or an alloy thereof.

3. The composition according to claim 1, wherein the Cu is in a greater wt % than (M*) wt %.

4. The composition according to claim 1, wherein the reinforced filler particles are ceramic filler particles.

5. The composition according to claim 4, wherein the (M*) is present in less than 55% wt in the composition, with Cu and ceramic filler particles making up 100 wt %.

6. The composition according to claim 4, wherein the ceramic filler particles are selected from a silica, alumina, tungsten carbide (WC), silicon carbide (SiC), silicon nitride (Si.sub.3N.sub.4), titanium oxide (TiO.sub.2), boron carbide (B.sub.4C), zinc oxide (ZnO), or magnesium oxide (MgO).

7. The composition according to claim 4, wherein the ceramic filler particles are present in the range of from 0.5 wt % to 10 wt %.

8. The composition according to claim 4, wherein the ceramic filler particles have an average longest dimension of 0.1 microns to 50 microns.

9. The composition according to claim 1, which is applied to the marine body at thickness of 200 microns to 1500 microns.

10. The composition according to claim 1, wherein there is an intermediary layer between the marine body and the composition.

11. A marine vessel, vehicle or craft, comprising at least one protective composition as defined in claim 1.

12. The marine vessel, vehicle or craft according to claim 11, comprising a hull which is in permanent contact with a marine environment, the hull being at least partially coated with said composition, wherein said composition comprises: ceramic filler particles in the range of from 0.5 wt % to 10 wt %; and a copper zinc (CuZn) alloy.

13. The use of a copper alloy composition of the form Cu(M*) to provide an antifouling composition on a marine body, wherein M* is at least one metal, which is more electronegative than copper, wherein said composition comprises ceramic filler particles in the range of from 0.1 wt % to 20 wt %.

14. The method of applying to a marine body the protective composition of claim 1, wherein said composition comprises a copper alloy composition.

15. The method according to claim 14, comprising the use of cold metal spraying to apply said composition to said marine body.

16. The composition according to claim 1, wherein the reinforced filler particles have a Vickers hardness in the range of 5 GPa to 70 GPa and include one or more of silica, alumina, tungsten carbide (WC), silicon carbide (SiC), silicon nitride (Si.sub.3N.sub.4), titanium oxide (TiO.sub.2), boron carbide (B.sub.4C), zinc oxide (ZnO), magnesium oxide (MgO), diamonds, carbon nanotubes, or graphene.

17. A protective composition for a marine body, wherein said composition comprises a copper zinc alloy and reinforced ceramic or carbonaceous filler particles, wherein said composition comprises zinc in the range of from 0.1 wt % to 35 wt %, and filler particles in the range of from 0.1 wt % to 20 wt %.

18. The composition according to claim 17, wherein the filler particles are selected from a silica, alumina, tungsten carbide (WC), silicon carbide (SiC), silicon nitride (Si.sub.3N.sub.4), titanium oxide (TiO.sub.2), boron carbide (B.sub.4C), zinc oxide (ZnO), magnesium oxide (MgO), diamonds, carbon nanotubes, or graphene.

19. The composition according to claim 17, wherein said composition comprises copper in the range of greater than 65 wt %, and filler particles in the range of from 0.1 wt % to 5 wt %.

20. The composition according to claim 17, wherein said composition comprises one or more first phases and one or more second phases, and wherein the copper and the one or more first phases are present in the range of 81 wt % to 89 wt %, the zinc and the one or more second phases are present in the range of 13 wt % to 15 wt %, and filler particles in the range of from 0.5 wt % to 1.5 wt %.

Description

[0053] An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings of which:

[0054] FIG. 1 shows a magnified SEM of composition 2

[0055] FIG. 2 shows an SEM of composition 1

[0056] FIG. 3 shows an SEM of composition 2

[0057] FIG. 4 shows an SEM of composition 3

[0058] FIG. 5 shows a table of results of Compositions 1 to 3

[0059] FIG. 6 shows deterioration of substrates and coated substrates post 1 year of seawater immersion

[0060] FIG. 7 shows a schematic of a cold metal spray apparatus

[0061] FIG. 1 shows a magnified image of SEM of composition 2 as indicated generally 11 wherein the distribution of Cu and phases of Cu.sub.xM*.sub.y 12, metal M* and -, , , , phases of Cu.sub.xM*.sub.y 13, and ceramic fillers 14 are present.

[0062] FIG. 2 shows the SEM of composition 1 indicated generally as 111 of the invention comprising 85 wt. % of Cu and a phases 112, 14 wt. % of Zn and -, , , , phases 113, and 1 wt. % of Al.sub.2O.sub.3 ceramic filler particles 114.

[0063] FIG. 3 shows the SEM of composition 2 indicated generally as 121 of the invention comprising 65 wt. % of Cu and a phases 122, 32 wt. % of Zn and -, , , , phases 123, and 3 wt. % of Al.sub.2O.sub.3 ceramic filler particles 124.

[0064] FIG. 4 shows the SEM of the composition 3 indicated generally as 131 of the invention comprising 45 wt. % of Cu and phases 132, 50 wt. % of Zn and -, , , , phases 133, and 5 wt. % of Al.sub.2O.sub.3 ceramic filler particles 134.

[0065] FIG. 5 shows the summary of mechanical, corrosion and biofouling test results of bare steel substrate and example compositions of the invention.

[0066] Hardness was measured using Shimadzu-MCT Vickers micro-hardness test machine. The polished cross-sections of the coatings were indented with a Vickers diamond indenter using 0.200 kgf (2 N) test load with a dwell time of 15 s, an average of 10 indents is considered as the representative coating hardness. Adhesion/cohesion strength of the compositions was measured as per ASTM C633 standard pull-off adhesion test. A three-electrode electrochemical cell consisting a 12 mm disc working electrode of the bare substrate and compositions, a graphite counter electrode, and a silver/silver chloride (Ag/AgCl 3M KCl) reference electrode was used for potentiodynamic polarisation test performed with a Biologic VSP-1371 potentiostat. All measurements were conducted in an earthed Faraday cage at ambient room temperature, 203 C. The electrolyte used was 0.6 M NaCl (3.5 wt. % NaCl) neutral salt solution with pH 5.80.3 and dissolved oxygen (O.sub.2) 5.60.7 mg L.sup.1 prepared freshly from deionised water. Potentiodynamic polarisations were performed between 400 mV to +600 mV vs. Ag/AgCl from open-circuit potential (OCP) at a potential sweep rate, dE/dt, of 0.167 mV s.sup.1. The test samples were immersed in a static 300 mL electrolyte for 1 h to achieve a pseudo-steady-state OCP before conducting polarisation tests.

[0067] The results shows that the mechanical strength of the compositions increased with the increase of Al.sub.2O.sub.3 and reduction of Cu and phase intermetallics. The hardness and adhesion strength of composition 1 with 1 wt. % Al.sub.2O.sub.3 and 85 wt. % Cu and phase intermetallics was measured as 1066 Hv.sub.0.2 and 102 MPa, respectively. The hardness and adhesion strength for composition 2 and composition 3 with respective Al.sub.2O.sub.3 content of 3 wt. % and 5 wt. %, and a phase intermetallics of 65 wt. % and 45 wt. %, increased to 13516 Hv.sub.0.2/247 MPa and 1438 Hv.sub.0.2/325 MPa, respectively. The corrosion rate of the example compositions shows an opposing trend, i.e. the corrosion rate slightly increases with the increase of Al.sub.2O.sub.3 particles and reduction of Cu and phase intermetallics. Composition 1 has the lowest corrosion rate of 28.91.7 m/y. It increases to 46.52.8 m/y and 65.53.2 m/y, respectively for composition 2 and composition 3. The corrosion rate of all three compositions is an order of magnitude less compared to the bare steel substrate which corroded at a rate of 205.82.5 m/y. The compositions also show more electronegative potentials 110510 mV, 114210 mV and 121510 mV, respectively, for composition 1, composition 2, and composition 3. In comparison the corrosion potential of bare steel substrate was 64010 mV, meaning that all compositions will offer sacrificial corrosion protection to the steel substrate in marine environment.

[0068] FIG. 6 shows the visual appearance of steel substrate and example compositions during one year long natural seawater immersion test with measurement periodicity of 4 months. The visual appearance of the test samples further validates the corrosion protection of the compositions discussed earlier. The steel substrate showed the worst corrosion appearance which worsened with the passage of time, conversely the compositions showed no physical material degradation of the composition surface. A controlled and active dissolution of Zn to Zn(OH).sub.2 sealed the surface of the coatings and protected the steel substrate on which these compositions were applied to. Additionally, the self-polishing nature of the example compositions presented Cu rich surface to the marine environment, which protected against biofouling attachment on to the coating surface. The area extent of the biofouling is shown in FIG. 5 table. In comparison, the surface of the bare steel substrate showed heavy biofouling. Within the composition, the composition 1 with 1 wt. % Al.sub.2O.sub.3 and 85 wt. % Cu and phase intermetallics showed the cleanest and more pristine surface, (lowest biofouling coverage % area in FIG. 5 table) further validating the excellent corrosion and antifouling credentials of this composition. In addition to self-polishing, the compositions also showed self-healing functionality. The results show that the composition can actively protect the substrates from corrosive and biofouling marine environment for long-term (>20 years), which the current state-of-the-art paint based coatings cannot.

[0069] FIG. 7 shows a cold metal spray apparatus 201, comprising a spray gun 208, with a gas heater element 203 and a carrier gas flow straightener 204. A source of compressed air 202 is controlled via a valve 207 into the heating chamber, wherein the air is forced out via a De-Laval nozzle 209. A powder feeder, feeds the powder 205 into the path of the gas flow, the powder comprising the compositions as described above. The powder 205 is then directed at a substrate 210 in a raster scan 212 to deposit a coating 211 of the feedstock powder on the substrate. The coating can be built up layerwise, with other powder, intervening or intermediary layers added. The powder 205 comprising the copper zinc alloys and ceramic particles.