Graphene-Based Coating for Corrosion Application

Chong, Luther Yuong Qai (2016) Graphene-Based Coating for Corrosion Application. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

Text Luther Chong Yuong Qai.pdf Restricted to Registered users only Download (4MB)

Abstract

The effects of corrosion in our daily lives can be both direct, in that corrosion affects the useful service lives of our possessions, and indirect, in that producers and suppliers of goods and services incur corrosion costs. Coating, which is one of the corrosion protection technique can be highly efficient to reduce the corrosion rate by isolating the underlying metal from the corrosive media. Graphene which is an extraordinary 2D carbon nanostructure has grab the global attention in corrosion field due to its excellence chemical properties. Graphene, which is an organic element can be coated on steel to isolate the metal from the corrosive environment. This project is to study the anti-corrosion performance of graphene (Gr), molybdenum (Mo) and Gr/Mo composite as a coating for galvanised steel. One step synthesis of coating for the tested specimens was utilised by applying electro-deposition method. There are two manipulated coating parameters which are the coating time and voltage applied. The unique part of this synthesis route is no acid was used for reduction process of graphene oxide (GrO). The material characterisation used in this project includes Scanning Electron Microscope (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), Raman Spectroscopy and Fourier Transformation Infrared Spectroscopy (FTIR). The coating of the specimen was evaluated by applying peel-off (ASTM D3359-09). Next, the coated specimens were further tested by immersion test (ASTM G31-72), salt spray test (ASTM B117-16) and potentiodynamic polarisation scan. The testing environment includes 5% NaCl and 2% H2SO4. In general, 5 V/20 minutes is the best coating parameter regardless of the coating material. Graphene coating has better corrosion resistance in 2% H2SO4 environment than molybdenum coating. This is due to the carbon to carbon bonds in graphene are so small and strong that prevent them from destabilisation of chemical structure. After applying graphene and molybdenum coating, with a coating parameter of 5 V/20 minutes, the corrosion rate of the steel was reduced by 37.19% and 25.25% respectively. On the other hand, under 5% NaCl environment, molybdenum has better corrosion resistance than graphene coated sample. This is due to the properties of molybdenum oxide which is highly immune to chloride ions. The anti-corrosion efficiency for graphene and molybdenum coated specimen is 32.84% and 43.77% respectively. Furthermore, Gr/Mo composite has the highest corrosion resistance in both 5% NaCl and 2% H2SO4 environment due to the composite integrate both advantage of graphene and molybdenum. The synergy effect from Gr and Mo matrix creates a protective layer which does not prone to the process of electron transfer since the polarisation resistance between steel and the corrosive media increases. Hence, the corrosion rate for Gr/Mo coated specimen has the lowest corrosion rate. The anti-corrosion efficiency for Gr/Mo composite under 2% H2SO4 and 5% NaCl is 54.73% and 52.94% respectively.