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Is there a method for plating steel with stainless steel?
If so, is it chemical, electrical, or electrochemical?
I did a quick search on the internet but was unable to find a service. I'm interested in applying a food safe finish to something that would otherwise be cost prohibitive to make out of solid stainless steel.
Keeping things simple, steel is an alloy of iron and carbon, whereas stainless steel is essentially an alloy of iron, carbon and chromium or iron, carbon chromium and nickel.
All forms of steel, whether they be ordinary iron and carbon alloy or stainless steel are made from a melt in furnaces. Because of this stainless steel cannot be plated to ordinary steel by chemical means either.
Stainless steel can be welded to ordinary steel but a TIG welder is required, but this wouldn't suit your purposes.
Hot dipping is unlikely to be an option due to the melting temperatures of ordinary steel and stainless steel. Depending on the type of stainless steel, the temperatures will be similar or higher for stainless steel. This would damage the main item made from ordinary steel.
Edit
In my initial answer I stated that electroplating stainless steel onto steel was not possible. Thanks to references to scientific papers supplied by @starrise and @Jaroslav Kotowski, it appears a form of stainless steel can be electro-deposited onto copper and stainless steel items. There was no mention of depositing onto ordinary steel. A deposit 23 um (0.023 mm, 0.9055 thousandths of an inch) thick was deposited in one set of experiments. I haven't found any references that claim the process have been commercialized.
If you can do a teflon coating, or if mild steel is not your only choice of base material, you may have other options.
There is a method for plating stainless steel with an Fe-25Ni-16Cr alloy which uses electroplating. The results from the article give a maximal electroplated layer thickness of 23 um. The properties of the electroplated alloy seem to be of similar quality to their reference sample of SAE 316 stainless steel. Electroplating stainless steel onto substrates is challenging specifically due to the required element chromium, which gives stainless steel its resistance to oxidative degradation. It is evidently difficult to create a stable, three element solution of Fe, Ni, and Cr due to the lack of a well-developed chemical complex for delivering chromium to the cathode. A quick Google Scholar search turns up 19 citations for that article, including one patent, which may be of further use.
There does not appear to be a commercial entity selling this particular service as of yet, that I could find. The typical turn-around time for materials processes from initial research to practical commercial application is on the order of 20 years, so you may have to wait some time yet (~2030) for this particular process.
You also can use mechanical plating (I'm not sure it's the right name) by basically rolling two sheets of metal together (Image) or Explosion welding
While it's not fundamentally impossible there in no real reason to do it as in most circumstances it will be more cost effective to either make the component in stainless steel throughout or to plate it with some other metal such as chromium or nickel. The problem is that stainless steel are quite complex alloys and plating processes generally work on a molecular level so there is a big challenge in plating the right proportion of the constituent elements onto the mild steel surface in the right structure and proportions as opposed to depositing a layer of just one elemental metal.
There are other approaches. HVOF, cold-spray, etc. can build up very thick coatings of a large number of materials (such as titanium, platinum, aluminum, stainless, plastics, etc) on almost any substrate - including paper, plastics, ceramics, and metals. The term coating is not expressive enough as these processes are also used to deposit tool steel to repair worn bearing surfaces, which are subsequently machined. Such techniques are not anisotropic as they rely on supersonic ballistic splatting of extremely fine powders.
Someone mentioned allclad plating with stainless steel. That is not quite correct. They take a pair of thin stainless steel pots, then position them to have a 1/8 inch gap, and pour aluminum into the void. Since the melting point of aluminum is so low compared to stainless steel, this works quite well, and the stainless pots do not deform.
