›
Please review the site Rules, Terms of Service, and Privacy Policy at your convenience. Rules, TOS, Privacy
Get familiar with the reaction system: Introducing the Reaction System

Metal , knife

Nicholas_23Nicholas_23
in DIY
Started polishing on a Medford knock off knife , getting down to some bronze copper looking layer ? The blade had that sandstone finish to it. 

Comments

  • Nicholas_23Nicholas_23
    Not sure if I should polish anymore? Didn't expect that
  • jhollanderjhollander
    Craig could probably tell for sure but my thought is that it's the copper dip before the chrome finish.  The blade edge should show any layers.
     John H, btw forum has decided I don't get emails
  • R-CarpenterR-Carpenter
    Chrome is usually plated over nickel which is plated over copper. It has to do with attraction and and strength of the chemical bond between different metals. I am not sure why the knife blade would be plated to begin with because plaiting works if it encapsulates the object. By default, the edge of the blade is exposed to the elements and the plating would degrade over time.  May be continue polishing and Toll Black it for a different look?
  • PWRRYDPWRRYD
    Copper is generally plated under trivalent chromium (show chrome) like on bumpers and shiny car/motorcycle parts.  It used because it is sort of self leveling and fills in scratches, pitting, and other imperfections.  It is easy to polish to a smooth finish because it is so soft.  Chrome shows every little imperfection in the base material so the copper/polish step is required.  Nickel is plated next because it is cheap and plates fast and is silver/blueish (opposed to the brown copper).  The chrome is plated last and is a very thin layer. 

    Hexavalent chromium (hard chrome) will plate directly to mild steel so no copper or nickel is required.  Stainless steel must have a nickel strike so chome will plate up. 

    Once in while we get a job where they want hard chrome on a cast iron part for extented corrosion protection.  We have to flash some copper on the cast iron first (just a tenth of a thousandth), then nickel strike the part, then chrome plate it.  Generally these are very large gate valves used in waste treatment systems and the like. 

    I have never seen a knife blade plated in our business.  I would guess knives to be forged, polished, case hardened, then the sharp edges ground, although they may case harden (quench) before the polishing step.  

    Some cutting and punching tools are nickel plated for corrosion and wear protection.
  • R-CarpenterR-Carpenter
    Where do you guys get the nickel? I buy from Casswell Plating in the small amounts but I am sure there's more of an industrial supplier.
  • PWRRYDPWRRYD
    We buy our nickel sulphamate directly from MacDermid Enthone.
  • PWRRYDPWRRYD
    I talked to our most experienced guy here (40 years in the business).  He said he has seen knives that are copper/nickel/chrome plated, but those were showcase knives that were never meant to be used or sharpened.  Not sure if that's what you have but it sure seems like it.
  • Nicholas_23Nicholas_23
    Ok, thanks for the info guys. I decided to put it back together and not mess with the blade anymore. Didn't want to totally destroy the blade
Sign In or Register to comment.