I have tested Al-CNT composites in 3.5% brain solution and found that corrosion rate though remarkably decreased but pitting tendency increased slightly?
Due to the galvanic serious the graphite most noble and the aluminum is the lowest in the chart . so the Galvanic cell will employed, CNTs for example between grain boundaries will push the grains to be anode so it will pitting gradually.
OK, it is obvious that galvanic action will be established to increase pitting tendency...
But what about corrosion rate, which became, in fact, better than pure pure Al??
Perhaps there is some influence of CNT on the passivating characteristics of the thin aluminium oxide layers present on the surface of the specimens
The reason for decreasing the general corrosion could be less effective metallic area in the case of Al-CNT sample due to CNT particles.
CNTs are added in very small quantity (0.1 to 1 %). such a small faction can decrease effective area?
Yes, it can. You can check the corrosion potential. It might have been increased by increasing the fraction of CNT which shows a more thermodynamically steady system.
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