I will start by saying that the hardest part to detail on the engine is the air cleaner bottom. The reason that it is so hard to do, is that it was barely painted at the factory, and by the nature of how it sits, it collects water and will rust badly. I have seen some where the bottom sealing lip is totally rusted away. In the first picture, I have already removed the bottom sealing rubber gasket using a flat bladed screwdriver to determine how badly this one was going to be. After removing the gasket, I did some preliminary rust scale removal with a wire brush. Then I brought it inside for decreasing and further cleaning. Keep in mind, that the inside of the bottom is only seen when you change the filter element, and the bottom is not visible on the car, so the only area that you have to be concerned with is the 1/2" lip that shows on both the outside of the lip and inside above the gasket.