The authoritative public forum
  for Metal Finishing since 1989
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Iron Electroforming

Q. Has anyone any experience of electroforming ductile iron to a thickness of about 60 microns? Any ideas gratefully received!

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2000

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Q. Can anyone provide me with a formulation for low stress stable ductile iron electroforming in thicknesses up to 0.5mm? I know it is possible from sulphate, sulphamate, chloride or fluoborate baths but I have to rule out the chloride and fluoborate baths for environmental/corrosion issues.

Robert Chilton
R.A.Chilton - Chester, UK
2001

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Q. I need some pure iron in tube form. Will I succeed trying to plate onto, for instance, a wooden dowel coated with carbon dust?

Paul Roberts
- United Kingdom
August 24, 2010

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Q. Hi!, "iron being plated on copper" is the same experiment we are working on at school. The problem for us is that we are trying to obtain the most uniform layer of iron possible on the copper wire. Is the process of electrochemistry sufficient to deposit a uniform layer of at least 95% percent yield? or is there anything we can add to compensate for a uniform surface area?

Ana-Patricia Lopez [surname deleted for privacy by Editor]
- Chula Vista, California, U.S.
April 3, 2009

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Q. Hi Guys,

Can one electroplate iron onto gold as well as it can be done on copper?

Kind regards,
Chris

Chris Rogers
- Toronto, Ontario, Canada
August 6, 2009

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Electroforming Iron onto a Fusible Metal Mandrel

Q. I wish to make molds to chill-cast high-purity aluminum for bright anodizing, using hot FeCl2 electrodeposition to make shell molds perhaps 3/16" - 1/4" thick. The plan is to cast the mandrels in Rotometals' 281-338F dimensionally stable alloy, polish them up, degrease and then smear with powdered graphite as a conductive anti-adhesion layer so that the mandrel will not "tin" the inside of the electroformed mold when melted out. I plan to adapt the periodic current reversal method of USP 2451341 to get uniform dendrite-free iron deposition.

Specific questions:
1) Does anyone have experience using graphite in this way, or if not, do they think it would work?
2) If I do get a "tinned" surface on the mold, would conc. HNO3 remove the coating of bismuth-based alloy and leave unharmed passivated iron?
3) Is Fe pickup from the mold by the molten aluminum likely to introduce enough Fe at the casting surface to stop me getting a mirror-bright anodized finish? (I know this is more of a foundry question, but maybe someone has tried to bright anodize Al permanent-mold castings).

Colin Braathen
Hobbyist - Gundagai, NSW, Australia
December 19, 2015

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January 31, 2016

Q. Hi Geoff (and Ted)

Thank you for giving my question consideration and responding. I am a backyard tinkerer not connected with the plating industry, and my choice of iron was based on ease of obtaining it and generating the chloride salt. I wouldn't know where to start trying to get nickel salts, let alone the metal itself, and given its toxic and potentially polluting nature, I would not be surprised if it is on a restricted list in this country. Also, I suspect nickel and its salts would be expensive and one would probably have to own a plating business to get it. A spillage of ferrous chloride, by contrast, is environmentally quite benign - the worst thing it puts into the environment is chloride ion - the whole of Australia is red with iron. And, importantly for me, its cost is only that of the HCl needed to make it. I have tons of scrap iron

There is quite a bit of literature going back about a century on iron electrodeposition; it was used to make tyre moulds for instance, and may be still for all I know. It was once used for reproducing banknote printing plates by the US Treasury. I agree that ferric chloride is not a good basis for plating; most documents on the subject stress the importance of keeping iron 3+ levels in the bath low. Air for agitation is likely to oxidise the ferrous ion to ferric, so I plan to hermetically cover the bath with clingwrap and agitate using argon from my TIG welding set as blanketing gas. The gas will be recycled to the sparger at the bottom of the bath using a 3000-litre/h aquarium pump off eBay . Net argon consumption should be small. Bath heating will be by quartz tube with a Nichrome coil inside, salvaged from a cheap radiant room heater, glanded into the bath walls with silicone. Bath lining will be PVC, heat gun welded at the seams and bonded to a support shell with air-moisture-curing polyurethane glue (bath temperature will be uncomfortably close to the glass transition temperature of PVC).

I, too, have plated iron from a sulphate solution as a tryout. I got about 1 mm before my power supply burned out (15A on about 0.5 sq.ft , i.e. 30 A/ft). The iron was brittle to the point of being crumbly I could almost crush it in my fingers, and I had incipient dendrites. A bit of annealing on a hotplate might have fixed the brittleness. I didn't think to add acid. One cannot buy sulfuric acid in this country any more, even for batteries, but a few chloride ions in the bath from HCl shouldn't matter. Chloride baths are run at higher temperature and, apparently, can produce a ductile stress-free deposit if done right.

PET (polyethylene terephthalate, Dacron) is surprisingly resistant to a wide variety of inorganic chemicals, and I plan to use it in the form of geocloth for an anode bag. The bath will be Fisher-Langbein, FeCL2.4H2O 300-450 g/l, CaCl2 150-190 g/l, 85 °C, pH 1.5, current density 2 9 A/dm2 (20 85 A/ft2). The low pH should help to minimize formation of the ferric salt. For a power supply to cover any sort of reasonable area, I will probably have to butcher a microwave oven transformer (~1200W) and do a multi-tap secondary out of copper strip, then rectify and filter. That should potentially give me up to 200A at a nominal 5V. Oh, and THICK cables.

I may try recirculating the bath through a Dacron filter, but I am not 100% sure about the aquarium/fountain pump I saw on eBay . The vendor boasts that it is corrosion-resistant, being made of plastic and 316 stainless. It is supposed to be OK for salt water, but hot FeCl2 + HCl is a whole other salt mix. I fear, at the very least, chloride stress-corrosion cracking.

Regarding current reversal, I will have a setup such that I can go from DC in one direction to DC in the other, with mark/space ratio continuously variable between. This will be accomplished with a diode/phototransistor looking at a specially shaped piece of Al foil on a slowly turning, speed-controllable black disc. The shape is formed from two opposing Archimedes spirals and is pretty much Ace-of-Hearts shaped, with the cusp at the centre and the vertex at the edge. With the eye near the edge, there is only momentary activation of the relay; with the eye at the centre, it is continuous. It will control a 30A DPDT relay (or two) for swapping polarity. At least I can give it a go and see what happens.

So that's the plan.

Colin Braathen [returning]
- Sydney, NSW, Australia

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Q. Hello! I do iron plating more than 2 years. Base of electrolyte is iron chloride. It is very tricky to adjust right parameters and right electrolyte balance, but for now all works great. Yes, there are problems with internal stress of iron; it can easy break the part. I work many years with copper electroforming; I make a lots of products with this process. In some parts I need more strength than copper can give, so I use iron electrolyte to grow up some 0,2-0,5 mm. I have lots of photos of this :)

Ignus Sudzhis
lemonpepperchrome - Latvia, Liepaja
March 27, 2019