4X4...
As I understand it, very few acids will actually etch-thru high nickel alloy oxides [especially those formed in-service]... and MOST of those acid-mixtures are the most dangerous and difficult to use in existence. YUCK.
Also, these surfaces develop a normal oxide layer due to oxygen and heat exposure... so IF stripped to 'bare metal' it will soon return to oxidized metal surface state... only cleaner.
Regards, Wil Taylor
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