Electroless vs. immersion vs. displacement vs. contact plating

A. In my opinion, the honest attitude is the most helpful to your customer. Tell him what you have told us, that you are not platers. He must find a professional plater for good quality and trouble-free service. Of course, you can sell the plater your tin salts.

A. Gentleman,
Using sodium stannate for Plating on to Aluminium Pistons is called Immersion Tin coating and not electroless plating.
you have to use 5% of Tin salt in water at a temperature of 80 to 85 °C. Just immerse the pistons, you will find a coating of Tin in 2 minutes.Then rinse and dry.
But the free caustic content in the bath should never exceed 5.0 gram/litre. For this the Sodium stannate should contain less amount of sodium Hydroxide for good control over the bath solution. Or else Blisters will appear on plating due high caustic content.
Thank you,

A. My experience is limited to nickel plating for clad steels but I do know Cadillac used this process starting in the 50's. You can find very detailed information by searching Cadillac restoration/pistons.

A. Hi Marvin. Thank you for advising me, in our previous discussions of immersion gold plating, about this method of assisted displacement plating. I've personally never made a distinction between 'displacement' plating and 'immersion' plating, and I don't think many others have either, so it is difficult to search for your topic of interest. But Finishing Publications / Metal Finishing Information Services (surfacequery.com) offers literature search capabilities for their extensive collection of abstracted metal finishing materials which may be of some help.

Regards,

A. I think you would find U.S. Patent 3,400,012 to Michael Golben interesting reading. While the teachings of this patent have been developed and improved significantly since its' publication (by 3M, MacDermid, Atotech, Tru-Plate, McGean, Plating Systems and others) the core process is widely used. Golben teaches the use of a salt of a more noble metal and a powdered active metal ('driving metal' as he calls it). Noble metals would include gold, silver, copper, tin, chromium and nickel; driving metals would include cadmium, zinc, magnesium and aluminum. The process would be most often conducted in an acid environment, often at an elevated temperature. Standard Electrode Potentials (sometimes the word 'oxidizing' or the word 'reducing' is substituted for 'electrode') will give a rough guide as to what is possible. However, there are some reactions that appear that they should work, but don't, and some that work even though it would appear that they shouldn't. (BTW, on reexamination, all of this patent's claims were canceled. You can order the file wrapper from the USPTO for details.)

A. Hi Pedram. We added your question to a thread about the distinctions between these different types of non-electrolytic plating processes. But the answer to your specific question is that hot-dip galvanizing is not an "immersion plating" process. Hot dip galvanizing is a high temperature process where the steel is put into molten (melted) zinc -- the process is more like hot-dip soldering or dipping strawberries into melted chocolate or dipping apples into melted caramel.

Regards,

A. Hi again Pedram. It is certainly confusing because the word "immersion" by itself does in fact mean essentially the same thing as "submersion", just as you say! But we'll have to disagree on what "immersion plating" means :-)

I hate to try the facetious logic of "argument by authority", but I must ... because I've been involved in the plating industry for 52 years and can't count the times the phrase "immersion plating" has been used over the decades, always meaning displacement of a less noble metal by a more noble one, never including autocatalytic electroless plating, and not demanding submersion (sometimes a single drop of a test solution placed on a surface forms an immersion plated deposit on that surface serving as proof or disproof of something).

When you look up "immersion coatings" in the index of the Electroplating Engineering Handbook [on AbeBooks or eBay or Amazon affil links] it says "see Displacement Coatings". In Parthasaradhy's "Practical Electroplating Handbook" there is a whole chapter on "immersion plating" and it's clearly distinguished from electroless plating. Finally some people do "ENIG plating" (electroless nickel plus immersion gold) and others do "ENEG plating" (electroless nickel plus electroless gold). Good luck.

Regards,

  Thank you again. In MY opinion immersion plating is a general term that can include both displacement plating or galvanizing by considering their different mechanisms. But you right, electroless plating is a different story.

A. Here's what Lewis Carroll wrote in Alice in Wonderland:

"When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean -- neither more nor less."

"The question is," said Alice, "whether you can make words mean so many different things."

"The question is," said Humpty Dumpty, "which is to be master -- that's all." (Looking-Glass 6.63-65)

And here's the interpretation from Schmoop (online):

Humpty Dumpy believes that he can exercise total control over language. Unfortunately, as Alice realizes, if he makes words mean anything he wants, then nobody can understand him. People have to agree on shared definitions and meanings for communication to be possible.

Disclaimer: Our company has a very large presence in the markets for immersion copper plating on steel and electroless deposition.