Abstract. The investigation of coating incorporated with various percentages of henna has been conducted by means of weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy method. Mild steel has been studied at ambient temperature and 50°C in order to examine the effect of temperature. The potentiodynamic polarization measurements indicate that henna extract acts as a mixed inhibitor while the corrosion rate (CR) value decreases as the current density (I corr ) decreases in the presence of 10% henna extract for both temperatures. Surface and protective film analysis have been carried out using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM).The inhibition activity is mainly correlated with the major active functional groups of lawsone. The main components can be found in lawsone structures are phenols O-H, carboxylic acid C=O and alkenes C=C. The morphology of the uninhibited sample showsa rough surface of mild steel as a result of corrosion process and severe damage can be seen. In the presence of henna, a smooth surface of mild steel anda uniform deposition of henna were observed.

Metallic materials are the most applicable materials in various industries. They are useful due to their excellent mechanical properties. However, they are exposed to corrosion because the environment contains oxygen, humidity and some other factors. This paper describes about a paint incorporated with organic inhibitor, i.e., henna extract. This paint was produced to enhance its anticorrosive property. Henna extract was chosen as the corrosion inhibitor as it is organic, environmentally acceptable, readily available and a renewable source of material for a wide range of corrosion problems. The extractions were characterised by using Fourier Transform Infrared. Meanwhile, the inhibitive action of henna extract was investigated through an electrochemical technique. The inhibitive effects of henna extract were investigated with percentages of 0%, 4%, 8% and 10% incorporated into a rosin (epoxy)-based matrix. The specimens were characterised by electrochemical impedance spectroscopy measurement. The morphology study was investigated through surface analysis by using scanning electron microscopy. The inhibition efficiency increased as the concentration of henna extract was increased. The results showed that Paint 3 has the lowest corrosion rate of 0.001767 mm/yr as compared to Paint 1 with 0.005148 mm/yr. The inhibitive action of the henna extract is discussed. Paint 3 was proposed as the most effective paint that contains a natural inhibitor for aluminium alloy.

The corrosion performance of aluminum alloy 5083 (AA5083) was investigated in the splash zone area simulated in salt spray cabinet at ambient temperature. Three paint formulations were prepared in accordance with different percentages of henna extract. FTIR method was used to determine the constituent of henna while weight loss and electrochemical method were applied to investigate the inhibition behaviour. The findings show that corrosion rate of aluminum alloy decreased with the increases of henna extract in the coating formulation. The rise of charge transfer resistance (Rct) value has contributed to the greater protection of the coated aluminum. The decrease in double layer capacitance value (Cdl) is another indicator that a better protective barrier has been formed in the presence of henna in the coating matrix.

Traditionally, zinc has been used as metallic material to protect steel against atmospheric corrosion. The coatings are used for corrosion protection in a variety of industrial applications. This is due to its ability to provide cathodic protection to steel in all types of natural atmospheres. In the effort of determining the optimum coating thickness, a comparative study of the corrosion on mild steel coated by different thickness of zinc in marine environment was carried out. This paper presents the corrosion study of two marine environment which are immersion in seawater and also in salt spray splash environment. The aim of this study is to compare by experiment the corrosion rate of mild steel coated by different thickness of zinc under salt spray and also immersion. The corrosion measurement test was performed by weight loss measurement, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. The morphological study on the surface degradation of the coated steel was performed by using scanning electron microscopy (SEM). The investigation on corrosion rate for the salt spray test shows higher loss percentage compared to seawater immersion. The bare mild steel recorded the highest corrosion rate compared to the other coated mild steel in both environments.

Henna is identified as an excellent corrosion inhibitor and due to this reason, a research project was conducted in order to investigate the ability of henna extracts to act as an anticorrosive agent with the compatible composition for paint systems. The paint composition consisted of colophony (WW types), plasticiser (oleic acid), pigment (calcium carbonate), solvent (mixture of xylene/white spirit) and additives (zinc oxide and henna leaf extract). These ingredients were mixed until they were soluble and stirred using a high-speed disperser. In order to measure the effectiveness of the new paint system, several nondestructive tests were conducted to investigate the inhibitive properties of henna extract including measurement of substrate mass loss. The inhibition efficiency (IE) increased with the increasing amounts of inhibitor. The highest IE (%) was 77.63% and this was produced by the paint with 8% inhibitor (P3). However, the IE value started to decrease when 12% of henna extract was incorporated into the paint matrix (P4: 58.40%). Thus, P3 acted as an optimum paint with respect to its performance on the corrosion inhibition efficiency based on mass loss measurement and electrochemical studies. Surface analyses were carried out using infrared thermography and scanning electron microscopy. These surface analysis test was carried out to support mass loss and electrochemical study. Based on the results, the performance of henna extract as a corrosion inhibitor on aluminium surface showed a great impact with the 8% of henna extract presence in the paint formulation.