NMC2006 Accepted 28/11/2006 CORROSION BEHAVIOUR OF AA2014/Al 2 O 3 p AND AA2009/SiCw IN SALT SPRAY TEST Y.B. Zamri 1,* , J.B. Shamsul 2 and K.R. Ahmad 2 1 Politeknik Tuanku Syed Sirajuddin , 02600 Arau, Perlis 2 Kolej Universiti Kejuruteraan Utara Malaysia Jejawi, 02600 Arau, Perlis Introduction Aluminum matrix composites (AMC) are currently being developed for engineering components because of high stiffness, elevated temperature properties and good fatigue resistance [1]. However, the restriction of AMC applications is the effect of the reinforcement on corrosion resistance. Previous corrosion investigations on AMC have shown various mechanisms such as high dislocation density around the reinforcement, voids at the interface between matrix and reinforcement [1], oxidized layer on the reinforcement [2] and segregation of alloying elements to the interface between matrix and reinforcement [3, 4]. The objective of this paper is to study the influence of NaCl concentration and surface roughness on the corrosion behavior of AA2014/Al 2 O 3 p and AA2009/SiCw. Experimental procedure Salt Spray Test was performed using rectangular specimen (dimension–15x10x4mm). The specimens were cold mounted within 5 mm above the bottom of salt spray to support the specimen in the vertical position. Before mounting, the specimen surfaces were ground to P180 grit, P400 grit and P600 grit using series of emery paper with water as lubricant. The surface area of the sample exposed to the salt fog atmosphere was approximately 4 cm 2 . Specimens were washed with ultrasonic cleaner, dried and weighed before salt spray test. Once the experiment was finished, the specimens were washed with distilled water to remove the saline deposit formed on the specimen surfaces. The specimens then dried with hot air and then weighed again to calculate the mass gain per unit surface area for the different times of the test. The salt fog atmospheres were 3.5 wt. % NaCl and 5.0 wt. % NaCl with pH range 6.5 – 7.2. The temperature of the salt spray cabinet was 50 0 C. Atomized air pressure of the saline solution was maintained at 100 kN/m 2 in the range of 69 – 172 kN/m 2 that recommended by ASTM B 117 standard. Results and Discussion Table 1 shows the kinetic laws calculated for all tests from the experimental data and perfectly fitted to a linear trend corresponding to growth of corrosion products layer generated after 20h exposure. The higher chloride concentration and surface roughness have increased the kinetic constant due to growth of corrosion products layer. Figure 1(a,b,c,d) shows SEM micrographs of composite AA2014/Al 2 O 3 p and AA2009/SiCw after been exposed to 3.5 wt% and 5.0 wt% of NaCl for 20 hrs. The surface roughness is P180 grit. It reveals the influence of NaCl concentration. Higher chloride concentration has promoted the growth of the corrosion product layer. Figure 2(a,b,c) shows the morphology of the composite surfaces which have been exposed with 3.5 wt% NaCl solution for 20 hours. It was noticed that the original Al 2 O 3 protective layer is completely covered by corrosion products. The corrosion product increases when increasing the surface roughness. 123