Want rust finish on forging

I have used Easy Rust (spray on) from Metal Finish Supply, Inc. for years on hot and cold rolled sheet and plate with good results. I need a cosmetic rust finish on a McCarr turn buckle PN 30045T47. The part is forged and described as high strength. I removed the galv finish via sandblasting but I get only a gray color even after it is exposed to moisture. On other items I can get a good rust finish in 12 hrs.

Any ideas on what I can use to get this to rust?
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