Zinc Electroplating

Hello All,

I am looking into DIY zinc electroplating / passivating for some mild steel parts a friend wants me to make for him. After a bit of googling there seems to be a variation of how to do this, including high corrosive acids and some dissolving the zinc in the bath pre-electrolysis.

One method I have read and hope to go for is:

Bath - 30g of zinc sulphate to 100ml of water

Electrolysis - stick 6 volts through a zinc anode and use the part to be plated as the cathode - I will see if my car battery charger will do the job.. What kind of current is required?

Hoping people can give me some advice here and lead me in the right direction before I shell out on eBay. For instance should I use distilled water or is tap water okay?

Has anyone read the Workshop Practice series on electroplating? Is it worth a read?

One thing worth mentioning is that these parts will have 3/8 threads on them and they will need to function after the plating.

Thanks

Thomas

Edited By Thomas Gude on 19/05/2014 17:06:26

Thomas,

It's just worth mentioning that Galvanizing is not an Electroplating process.

Sorry, I can't help regarding Zinc Electoplating, but I'm hoping to learn from others' replies.

MichaelG.

Plating/coating in general can cause threads to jam if the plating thickness is too great. I do some work with a company that occasionally makes specialist coated fasteners, they deliberately make the threads to the 'slack end' of tolerance so that the coating give finished parts to the required fit (whilst still meeting strength spec).

ah thanks Michael, post edited

Michael

Just to confuse the issue the process of zinc electroplating is sometimes referred to as electrogalvanisation see the Wikipedia page here and a commercial page here. There was also a pdf file which looked quite interesting but it was pretty large so I refrained from linking to it. I prefer the term galvanizing to refer to the 'Hot Dip Galvanizing' process and electroplated zinc for the other as it, to me anyhow, clearly differentiates between the processes

Cheers

Martin

Edited By Martin W on 19/05/2014 18:08:36

There is one other way to apply a coating and that is hot spray coating a bit in between hot dip and electo plating

Bob

I know a chap who restores banjos. He does all his bright nickel plating using a 'plating pen' with excellent results.

Neil

.

Fair point, Martin ... I suppose it just goes to show the language evolving !!

I agree with you regarding a preference for clear differentiation of the processes.

MichaelG.

.

But is there one available for Zinc ?

MichaelG.

I have done zinc plating using the recipe given in the Workshop Practice book No 11 by J Poyner. the electrolyte is 30 g of zinc chloride and 120 g of ammonium chloride per litre. Plating is carried out using a zinc anode. The current density is quite critical to get a good bright coating and I found about 12 amps per square foot was about right. I made a small transistor variable current supply to control the current.

The book by Poyner is very good and goes through all the requirements for cleaning the article before plating.

Mike

You can also do mechanical zinc which does not involve electrolysis and does away with embrittlement issues - most nuts and bolts etc are done like this.

Mark

> But is there one available for Zinc ?

Indeed there are pens for a whole raft of metals, my understanding is that if you can electroplate it, you can use a pen to do it. I think they are probably the most effective route for small parts, especially if you are worried about losing detail.

**LINK**

Neil

Thanks, Neil

Very useful link.

MichaelG.

Sounds great, although I am not quite sure how to set this up in the home workshop easily.

The-online-retailer-who-shall-not-be-named are selling the book for peanuts so I think I will buy it and have a crack at what it says.

Cheers

Thomas

I had a kit off 'gateros' on ebay . I have successfully plated many parts and surprised myself on a number of occasions with the quality of the job. Most of the chemicals you need are in the kit.

1 caustic dip to de grease

2 rinse in water

3acid etch to prepare surface

4 rinse in water

5 plating bath

6 rinse in water

7 dip in brightner

8 rinse in water.

I'm sure you can amass all the chemicals and materials cheaper individually but I found the kit excellent

plus they give advice over the phone. Plating book good , if somewhat technical. I used an old school type psu , voltmeter and ammeter . The trick is to keep voltage about 2 volts and moderate current dependant on area to be plated. If it all goes wrong you can acid strip it off and start again. I used bits of copper wire to suspend parts hanging off a metal bus bar type .

You would need some plating media which is fine glass balls (like glass bead blast grit) and the zinc rich chemicals. You then need something to tumble the whole lot in - like a cement mixer without the flights. You could cobble something together on a small scale using a small plastic drum - like a large 5 ltr swarfega bottle - and some form of motivation to make it tumble, something cobbled on the lathe perhaps?

Mark

ps. the media we used to use was about .25 or .5 mm dia beads if memory serves

Edited By Mark C on 20/05/2014 10:43:04

Hi All

There is also Sherardising:

Mechanical with sub melting point heat.

**LINK**

I have worked with parts made with this process. In particular door furniture... Locks and hinges.. You can still get it done well in France at least, you get a nice even matt coat.

Ah Ha... and in the UK too  https://www.google.com.au/#q=sherardising%20uk

Regards
John

Edited By John McNamara on 20/05/2014 13:51:08

Once experimented with zinc plating some bolts from a car chassis. Simple procedure - degrease with caustic soda solution, wash (tap water), pickle in hydrochloric acid until all rust removed, transfer to plating bath - zinc chloride solution - probably fairly concentrated. Zinc anodes probably obtained from dry batteries. Power supply was a bench adjustable 0-24v probably 1 amp max.

The result appeared to be successful but rather rough. From what I read this roughness is due to using a smooth DC power source - the plating tends to grow whiskers. Using an AC source combined with a DC offset should produce a more even finish. The brief current reversals remove the whiskers.

Never took this any further but if you want a confidence booster I still have a couple of the bolts sitting in a jar on the shelf - no rust after at least two decades.

PS:- Wash well after plating - the zinc chloride is corrosive.

Mike D

Seems I'm the only one hearing Luigi Galvani rotating in his Grave?

Even if this comes from a serious firm, what they write is wrong nonetheless.

Regards, Frank

Hi Frank

Perhaps his coffin was zinc rather than lead lined . The problem is that terms galvanised and galvanised iron/tin etc. became exclusively associated with the predominantly used hot dip process and by default galvanised was used to describe that process. Now the other processes are becoming more common/affordable that use electroplating and vapour deposition to achieve a more controlled and possibly better coating process and these do essentially the same job in bonding zinc to a metal substrate, all galvanised.

Well that's my take on it. I for one won't be galvanised into action listening for restless bones rattling in their zinc lined casket .

Martin