2 pack clear paint (which is basically what the POR 15 stuff is they just use a fancy name) or even acrylic clear is fine and works. The oxidisation originally occurs when there is a nick or chip in the clear and then moisture gets in and corrodes under the clear. The key to stop this coming back once you have cleared it is to bake the parts to get the moisture out the pors before you clear coat it. It can look all shiny and nice after polishing and then you paint it clear but 2 weeks later white corrosion occurs under the alloy and you havent even chipped it! this is because of trapped moisture in the pors after many years. You gotta heat them up to dry out the microscopic pors. I have found just leaving them in the hot sun for a week or so or under the fire inside for a few nights has been enough or you can stick the parts in the oven inside. You also gotta degrase them well so the paint sticks well use de-wax and thinners and maybe contact cleaner after initially using de-greaser, detergent and water to get the polish off and then i even wash them in boiling hot water aswell if i feel its needed as the pors dry out quicker thatway. I go though a rigourouse procedure to ensure the alloy is ultra clean and grease free before appliying the clear.
Frosty, the jap stuff is usually clear coated or it might be silver paint. Test with a multi meter if your unsure. if it buzzes its bare alloy which means the original clear has come off or been removed or it never had any. If it doesnt buzz its painted or annodized. Simple check to rembember if your unsure by just looking at the part.