Zinc Electroplating

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  • #23311
    Thomas Gude
    Participant
      @thomasgude37285

      How’s my set up?

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      #152946
      Thomas Gude
      Participant
        @thomasgude37285

        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

        #152947
        Michael Gilligan
        Participant
          @michaelgilligan61133

          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.

          #152948
          David Jupp
          Participant
            @davidjupp51506

            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).

            #152949
            Thomas Gude
            Participant
              @thomasgude37285

              ah thanks Michael, post edited

              #152951
              Martin W
              Participant
                @martinw

                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

                #152954
                Bob Brown 1
                Participant
                  @bobbrown1

                  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

                  #152957
                  Neil Wyatt
                  Moderator
                    @neilwyatt

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

                    Neil

                    #152958
                    Michael Gilligan
                    Participant
                      @michaelgilligan61133
                      Posted by Martin W on 19/05/2014 18:07:28:

                      Michael

                      Just to confuse the issue the process of zinc electroplating is sometimes referred to as electrogalvanisation …

                      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

                      .

                      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.

                      #152959
                      Michael Gilligan
                      Participant
                        @michaelgilligan61133
                        Posted by Neil Wyatt on 19/05/2014 18:29:45:

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

                        Neil

                        .

                        But is there one available for Zinc ?

                        MichaelG.

                        #152961
                        Michael Cox 1
                        Participant
                          @michaelcox1

                          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

                          #152962
                          Mark C
                          Participant
                            @markc

                            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

                            #152965
                            Neil Wyatt
                            Moderator
                              @neilwyatt

                              > 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

                              #152967
                              Michael Gilligan
                              Participant
                                @michaelgilligan61133

                                Thanks, Neil

                                Very useful link.

                                MichaelG.

                                #152980
                                Thomas Gude
                                Participant
                                  @thomasgude37285
                                  Posted by Mark C on 19/05/2014 19:35:28:

                                  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

                                  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

                                  #152985
                                  stevetee
                                  Participant
                                    @stevetee

                                    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 .

                                    #153003
                                    Mark C
                                    Participant
                                      @markc

                                      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

                                      #153017
                                      John McNamara
                                      Participant
                                        @johnmcnamara74883

                                        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

                                        #153020
                                        TobaccoBurner
                                        Participant
                                          @tobaccoburner

                                          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

                                          #153022
                                          Frank.N Storm
                                          Participant
                                            @frank-nstorm18349
                                            Posted by Michael Gilligan on 19/05/2014 17:03:15:

                                            Thomas,

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

                                            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

                                            #153027
                                            Martin W
                                            Participant
                                              @martinw

                                              Hi Frank

                                              Perhaps his coffin was zinc rather than lead lined wink. 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 wink 2.

                                              Martin

                                              #153034
                                              Michael Gilligan
                                              Participant
                                                @michaelgilligan61133

                                                Posted by Frank.N Storm on 20/05/2014 16:14:46

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

                                                .

                                                I sincerely hope so, Frank

                                                The inclusion of Galvani's name relates to the mode of protection provided by the Zinc, not to the method of its application.

                                                MichaelG.

                                                #153065
                                                Michael Gilligan
                                                Participant
                                                  @michaelgilligan61133

                                                  Having just reviewed my response to Frank, I think perhaps I should explain my thinking a little further:

                                                  There will invevitably be "an exception that proves the rule" but; in general Zinc Electroplating produces the thin layer commonly referred to as BZP, whereas Hot Dip Galvanizing produces the thick layer that we see on pipes, railings good buckets, etc.

                                                  BZP is too thin to provide much by way of Galvanic protection, and is really only a decorative finish that protects components on the shelf, or [at best] against light handling.

                                                  It is presumably possible to electroplate a thick layer but, in my limited experience, anything that requires serious environmental protection would be Hot Dip Galvanized.

                                                  MichaelG.

                                                  #153098
                                                  Frank.N Storm
                                                  Participant
                                                    @frank-nstorm18349

                                                    Thanks for the explanations Michael, one learns something new every day…

                                                    Having perused several flavors of Wikipedia, it really seems tat in the English speaking world galvanizing is used for the hot dip process. But I stay with my opinion that in my neck of the woods this is not the case.

                                                    Please see here:

                                                    Galvanotechnik

                                                    Pictures

                                                    I rest my case now.

                                                    Regards, Frank

                                                    #153116
                                                    Ian S C
                                                    Participant
                                                      @iansc

                                                      Until a few years ago, if you wanted a fine finish that resisted corrosion you went for cadmium, what happens now?

                                                      Ian S C

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