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In this age of globalisation, decreasing synthetic resources have exhilarated global communities to apply natural fibres as substitute materials for green technology development. The growth of products from lignocellulose fibre-reinforced composites has been a wide topic among material scientists and engineers due to their abundance, sustainability in nature, biodegradability, and availability at low cost. A series of natural/synthetic hybrid fibre-reinforced composites are prepared by reinforcing polyester resin as the matrix. Natural fibres such as sugar palm/kenaf/bamboo with fibreglass/Kevlar hybrid composite materials were used in this research to determine the mechanical and water absorption properties. The difference between the weight content of natural fibres which were 0 (control sample), 15, 45, and 60 wt% influenced their strength of mechanical properties. The Charpy impact and tensile test were performed following the ASTM D6110-10 and ASTM D3039, respectively. A water absorption test in accordance with ASTM D570-98 was also performed on three different natural fibre-reinforced hybrid composite materials to determine which composite had the best water resistance property. The results showed that hybrid fibre-reinforced composite for 45 wt% kenaf fibre possessed better tensile properties and 60 wt % sugar palm fibre performed better during the Charpy impact strength test compared to other natural/synthetic hybrid fibre-reinforced composites. It was concluded that sugar palm fibres demonstrated the best water resistance in this study.

The inhibition performance of citrus x aurantiifolia extract (CXA) on the corrosion of mild steel in 1.5 M H2SO4, 2 M H2SO4, 3 M H2SO4, and 4 M H2SO4 solutions was evaluated by weight loss, potentiodynamic polarization techniques, and scanning electron spectroscopy equipped with energy-dispersive X-ray spectroscopy. CXA inhibited the mild steel corrosion in the sulphuric acid solutionswith optimal inhibition results of 96.06% in 1.5 M H2SO4 and 86.57% in 4 M H2SO4 from weight loss measurement. Weight loss, potentiodynamic polarization, and scanning electron microscopy tests confirm the inhibitive performance of this compound and the increase in inhibitor efficiency increases with inhibitor concentration. The polarization data showed that the inhibitor acts as a mixed-type inhibitor, and fits the Langmuir adsorption isotherm. The adsorption studies clarify the excellent adsorption of this compound on the mild steel surface. The inhibited steel in the acid solution displayed improved surface morphology due to the surface protection effect of CXA molecules. The citrus x aurantiifolia studied here easily mitigates the effect of stress corrosion cracking on mild steel in a sulphuric acid environment. Keywords: Mild steel, Stress corrosion, Adsorption, Corrosion inhibitor, Sulphuric acid, Citrus X Aurantiifolia

This study enveloped innovative uses of a hybrid agro waste and silica carbide incorporated with aluminium as a new hybrid composite materials for marine application. In this study, the purpose of adding coconut shell powder (CSP) from the agro waste and silicon carbide (SiC) as reinforcement aluminium composites materials for combating corrosion problem. The CSP was incorporated into the molten aluminium alloys varies from 0%, 5%, 10%, 15% and 20% of weight percentages. The corrosion behaviour was determined by weight gain measurement (WGM), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP). As a results, 5% CSP reinforcement in hybrid aluminum composites contribute to excellent corrosion resistance performance by shifting the polarization curve towards the positive region, increases the value of polarization resistance, R p and reduces the I corr value. It can be concluded that, by adding CSP into aluminium composite has significantly increase the corrosion resistance towards a severe biofilm attack.

Commercial henna (Lawsonia inermis) was investigated to inhibit the corrosion of aluminum alloy through immersion in seawater. The aluminum alloy (5083) was prepared in size of 25mm x 25mm x 3mm. The immersion test was conducted in seawater with different concentration of henna, 100ppm, 300ppm, 500ppm for duration of 60 days. Four characterizations were performed in this study which was weight loss study, Fourier Transform Infrared (FTIR), Electrochemical Impedance Spectroscopy (EIS) and adsorption isotherm. The results indicated that henna has major constituents of lawsone which contributed to the chemisorptions or adsorption process by forming an isolation layers on the aluminum alloy surface which follows the Langmuir adsorption isotherm. It was found that the protection layer attached on metal was not permanent and precipitation occurred as the time increases. The highest inhibition efficiency was found at 88% (500ppm). This research found that henna is an excellent natural inhibitor for aluminum alloy in seawater.