How to remove phosphate coating from hardened cast iron.

Trying to detect grinder burn on the surface of a induction hardened nodular iron part. The surface, before phosphating, is fine-ground.
Is there an "easy" chemical removal method, or a light hand-polish with 400 grit sandpaper the only way to go?
The objective is to get a clean metal surface for a chemical etch to reveal any grinder burn.
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Any plating house can do the job chemically You can also use fine mesh abrasive blasting to clean the part. The check for burns should have been done before the phosphating process.
You could also check for cracks. Improper grinding which heats the surface too much may cause minor cracks which can be detected using NDT testing such as magnetic flux.

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electro-chemical

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