There is no way to chemically remove the corrosion. It has to be removed using mechanical means, i.e., wire brushing or grit blasting.

Some of the white (or green) stuff is silicate deposit. I believe this can be chemically removed using a citric acid flush.

The worst was the last photo. Was that a small piece that can be grit blasted? The first two look like they can be handled by scraping and wire brushing.

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95 E320 Cabriolet, 169K