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In electroplating, What is a 'Strike Solution'?
Q. Is it possible to apply strike on a substrate that will be used at high temperature (strike before applying the desired metal electroplating)?
... because I heard that it can cause some issues at high temperatures.
- Melborne
October 24, 2022
A. Hello A. The main reason for using a strike solution is to improve adhesion. I personally can't think of a situation offhand where applying a strike solution would reduce the usability at high temperature.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. Hello,
Just for example: Silver plating typically uses Copper or Nickel strike under Silver layer. However if plating is intended for high temperature applications, only Nickel strike is used.
- Winnipeg, CANADA
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Q. Tried looking it up, but even google didn't help...
Ray Avedianteacher - Los Angeles, California
July 5, 2012
(to help readers more quickly understand the Q&A's)
To plating industry folks, "immersion plating" or "immersion deposit" does NOT refer to whether the parts are dunked into the plating tank vs. plated with the brush/tampon method.
Rather, it indicates a situation where the metal dissolved in the plating solution is more noble than the metal of the component and will displace it without any electricity applied. The familiar school science project of placing an iron nail into a solution of copper sulphate [on eBay or Amazon]and having copper spontaneously plate out onto the nail is an example of "immersion plating". In most but not all cases "immersion deposits" are undesirable because their adhesion tends to be poor.
"Electroless plating" or "autocatalytic plating" is neither electroplating nor "immersion plating". It is a third type of plating where reducing agents are included in the mix which "spring load" it and the deposition of metal is catalyzed/triggered by the newly deposited metal itself. One major advantage of electroless/autocatalytic plating over immersion plating is deposit thickness because the catalytic reaction can continue rather indefinitely, whereas with immersion plating once there is a very thin film of the deposited metal covering the part, no substrate metal can go into solution to keep the displacement reaction going.
A. Hi Ray.
Indeed, in the early days Google would only show pages which included every search word you gave it. They dropped that idea in order to promote shopping over finding technical info. Oh, well.
A strike solution is a low concentration plating solution intended to form a thin initial plating layer which could not be formed or would be poorly formed in a full strength solution. Two typical examples: 1). Silver is a noble metal that tends to "immersion deposit" onto other metals with no electricity applied, resulting in a poorly adherent deposit. To deal with this, part of the approach is to do an initial thin layer in a dilute silver "strike solution" and then follow this up with heavier silver plating from a stronger solution. 2). Plating with good adhesion onto stainless steel is difficult because a passive oxide layer immediately forms on the stainless -- and you want to plate onto metals, not onto oxides. Very acidic but somewhat dilute nickel plating solutions called "Wood's Nickel Strike" or "Sulphamate Nickel Strike" can simultaneously dissolve the passive layer and deposit a fresh but thin nickel layer on it, which allows subsequent electroplating with nickel or other metals.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Thanks, Ted. Answered the question perfectly, but just to be clear: is the layer put on by the strike solution an immersion deposit as well, or is it electroplating?
Ray Avedian- LOS ANGELES
A. Hi again.
In the two examples that I gave, the strike processes are electroplating processes not immersion plating processes, but autocatalytic processes like electroless nickel may occasionally be used as a very thin 'strike' layer. There may be an immersion plating process of two that is called a strike, but I can't think of an example.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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