Unwanted etching with Turco?

[3/16th's]

Ever since my heat treaters have switched from foil to Turco, I have knives coming back to me with various degrees of unwanted etching. I am using 440C stainless. Some etching I can buff/sand out, some are way to deep and I am stuck with an ugly black mark(s). As far as I remember, I never had this problem with foil. I am positive the heat treat process is right. I am wondering if they are doing something wrong when they apply the Turco? Any ideas? Also, would overheating the steel when grinding have anything to do with etching during the heat treat?

Hugh

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King of all that rhymes with Orange!!!

 

[Gerome Weinand]

i have been using turco for 12to15 yrs. you have to have all the scale ground off but i like to have it ground no finer than 120 grit allso i thin it out real thin and dip ittwice you cant have any burn spots on them either i use mostly dendrictic d-2 i allso heat treat 440 ATS carbon steel any way i would never go to foil its a real pain in the ass

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