Zinc Plating Parts

I recently had a batch of parts zinc electroplated and am very pleased with the results. 

Shiny!

You have probably noticed that a large number of the bolts, nuts, washers and brackets on your car are gold colour. Or at least that they have the mottled and rusty patina that suggests they might once have been gold.....

Searching for 'gold'

Can you see it?

Back in the day, it was common practice to for such fixtures and fittings to be electro-plated plated in cadmium to provide a rust resisting layer. Very much in the same way that many bolts are shiny silver colour - 'BZP' - or 'bright zinc-plated'.

While a non-plated bolt will do the job just as well (and a stainless steel bolt will do the job even better) lots of D owners like the look that a little gold gives them under the bonnet. 

Attention to detail: Len Drew's car

I'm definitely not aiming for a concourse standard restoration, I'm happy for my car to look it's 54 years, but I would like it to to look a good 54, not a poor 54.

It's possible to get parts re-plated, just as it's possible to get parts re-chromed. However cadmium plating is all but banned or discontinued these days due to the toxicity of cadmium. While it's in the air and in the food we eat and is in things such as rechargeable batteries, it's pretty nasty stuff. It's the vapours and dust that are harmful and it's associated with lung cancer. Though it is still used in some industries, it's not really suitable for the hobbyist. The alternative is too go for zinc electroplating plating, finished with a yellow/ gold passivate. Cadmium is closely related to zinc and is found in zinc ore.

At it's most basic, the zinc electroplating process involves a small electric current being passed through an electrolytic solution (a conductive solution with free zinc ions). The negative terminal of the power supply is connected to the thing to be plated (so it needs to be able to conduct electricity!) and it is suspended in the solution. The positive terminal of the power supply is connected to a zinc bar. The current causes the zinc bar to slowly dissolve and the liberated zinc movs through the electrolyte to collect on the surface of the item being plated. 

The basic plating process
(image copyright - Mammoth Memories)

 

When zinc plating, initially the parts will come out bright silver, however a short dunk in 'yellow passivate' leaves them looking gold. Other passivate colours are also available.

Some caveats: Firstly, electroplating is not a magical restoration solution. It can restore the LOOK of a part, but not the part itself: a rusted and pitted bolt will still be pitted after plating. In fact the acids need to clean parts for electroplating may well leave the pitting and part looking worse than you thought it was. Secondly, electroplating will not last forever. It will provide added corrosion resistance and remain yellow for some time, but will eventually fade or corrode itself - just like the original cadmium finish did.

Notice that the pitting remains....

There are any number of small businesses that do plating and they will mostly be happy to take business for car and motorbike parts. Plating can be expensive - or at least prices can vary wildly - and, to get the best value, you really need to take a large number of parts along and negotiate a price. As I worked into my restoration, this didn't suit me for three reasons. Firstly there is HUGE variation in the size and shape of the bolt and washers used around a DS and I didn't want to muddle parts up. Secondly I was doing a gradual rebuild and I didn't want to have to strip everything just to amass a suitable number of parts to make plating worthwhile. And lastly I was reluctant to entrust valuable or hard to come by parts to strangers.

So....I started out by home plating with a DIY kit. This meant investing in appropriate chemicals, containers, pumps, heaters, thermometers and a power supply. There are starter kits readily available from websites and through Ebay etc.

Example of a DIY starter kit

The chemicals are only part of the cost. You also need to factor in pumps, heaters and the power supply. Others have gone into this big time and have set ups I can only dream of. Or I can visit their websites:

A semi-industrial set up
(photo copyright Citrothello)

My set up was more modest.....

Plating in the garden shed - 2016

New workshop, same set up - 2018

Home plating was very involved considering the small batches I was plating. It involved warming chemicals and using small pumps to get them flowing. The during of plating is important, as is the duration of the passivation process that leaves the parts gold colour. The cleaning and preparation was laborious but was a crucial part of the job. As was the de-greasing. Everything has to be hung on wires. That said, initial results were very good.

Zinc plating carburettor parts - 2018

Before plating

After DIY plating

.....but gradually my chemical bath turned dirty and soupy and the results were unpredictable. This was almost certainly down to a lack of maintenance of my chemicals on my part, but was indicative of the time and effort that needed to be invested, just to plate a handful of screws every now and again. 

Soupy......

There were several parts I wanted to plate that I always knew were going to be too big or awkward for my home set up. Keen to see how a professional plater compared to my efforts, I searched around and eventually found a plater in a nearby town. The price they quoted was significantly higher than I thought it would be but, for pieces that I could not plate at home, I felt I had little choice.  And I was curious! Looking at what I got back, the results were okay.......

A batch I had plated by a professional - summer 2019

.....but they lost a few small pieces. Nothing important but it said something to me about their quality control. I went back and they managed to fish a couple of missing bits out of their tanks - but they were so corroded they were unusable . 

These used to look quite good!

All in all it was an expensive and disappointing experience and I decided I would not use them again. As my rebuild continued, I went back to my DIY set up but the results were hit and miss. Plating continued to bug me and, as I was close to putting the car back together and wasn't willing to have the scabby old parts staring up at me from the engine bay, I knew I would have to bite the bullet one day. 

My car is a 1968 model and so the threads on the M5 bolts and nuts are 'ISO' standard 0.75mm pitch, not metric standard 0.8mm pitch. At the beginning of this year - and with reassembly firmly in sight - I was able to buy a number of old Citroen stock M5 bolts of the right pitch. However some were gold - cadmium plated - while others were plain black. When i bought them I had expected them all to be gold finish.

M5 set screws. 0.75mm pitch, but black.....

These proved to be the trigger for re-investigating zinc plating. I realised that I had so many parts still to be plated, that I couldn't do it at home. It would slow my overall progress. I decided to commit to farming the work out to a professional plater. Searching again, I found a plater on the other side of my home town. Less than 15 minutes away! Had I missed them first time around? Were they a new business? I think I had tried to contact them before never got through by phone so assumed they were out of business. I managed to speak to someone this time around and they were willing to take on the job.

I knew that any negotiation over price would be dependent on the number of parts I offered up, and that they would need to see the parts in question. It was going to be a difficult equation: finding enough parts to make plating worthwhile, but not so many that the total cost was crippling. So, with that in mind, I set about amassing all the parts I could think of that were going to need plating. That took a long time.....

As I have dismantled my car over the years, I have stored parts in more than 50 different boxes. Plus various nooks and crannies. And the attic. Oh, and the garden shed. I don't think there are parts under our bed anymore. While I maintain a reliable spreadsheet of what parts are in what boxes, I still needed to hunt through them all to find the bits to be zinc plated.

Needles in haystacks

Then, as I was removing the relevant parts from the boxes, I needed to keep a note on my spreadsheet of what had come from where so I could put them back in the right places after plating......

Some parts I wanted to plate were still attached to other parts that didn't need plating - so further searching and disassembly was called for. 

Some dismantling was needed

Air horn bracket. That'll want plating.......

These extra pieces needed to be added to my database and a note made that they had been removed for zinc plating..... Eventually I got a good pile of parts together.

A lesson I learned from my DIY plating efforts was that the finish you get is only as good as the preparation. While the platers will use a chemical 'pickle' to clean the parts, this is mostly to remove grease, not the crusty scale from corroded cadmium. So, everything was degreased using Jizer, grouped, then counted and photographed.

Cataloguing. Notice the traces of cadmium remaining on some parts

Then, in batches, I cleaned everything on a wire wheel. This removed crusty scale and any remaining traces of the original cadmium coating. I reasoned that the platers probably wouldn't and couldn't do this (time is money after all) and so if I wanted good results, I would need to put some effort in. Remember that Cadmium is nasty stuff, so it's important to wear a face mask if you choose to do this.

These are all the parts I amassed. The majority were going to be gold - yellow passivate - but a few were just going to be shiny silver finish. Allowing for the wheel nuts, bolts and washers in bags, I think there were many, many pieces in this pile as I took to the other plater several years before. There were at least 500 bolts, nuts and washers.

Ready for the plater

I found my local plater really friendly and helpful and I'd be happy to go to them again. He eyed up all the parts and gave me a price that was less than the price I'd paid several years previously, for more than double the parts! So the price was right, and the results were great too! Not a single one of the 500+ bolts, nuts and washers was missing, and they had all been individually hung from wires for the plating process. That's a lot of time and cost right there. 

All done!

I really am pleased with the results. And I'm sure all the effort I put into cleaning all the parts beforehand added to the quality of the finish.

Before

After

Also, the effort I put into getting to this point, should pay me back by virtue of a more straightforward assembly process - all the cleaning has been done. I'm sure as my build continues, I will find a few parts that I missed and should have had plated, but I'll cross that bridge when i come to it. 

Removing Underseal From The Underside Of The Chassis (Part Four)

Phew! I finally finished stripping, cleaning and repainting the underside of the car. That's only the flat horizontal side mind you - the bit you won't see! 

I'm using a two part epoxy paint applied with a roller. It's just a primer and can be top coated but it looks as though I'm not bothering and will just add a layer of underseal.

Two-part epoxy primer

Applying it with a roller is the recommended approach. It leaves a slightly textured finish but, as I eventually plan to coat the lot with underseal anyway, it doesn't matter. As its going to be visible, the engine bay and rest of the chassis will be painted using a different paint system to give a smoother finish. 

The last stage of the underside repaint was the area beneath the front footwell and the two front 'tusks'.  This area was the hardest to do. Partly because it's not just a flat floor pan, and partly because of all the engine oil, grease, LHM and road dirt that had accumulated there. 

Last stage...

I'd been working on this last part on and off for a couple of months now, multi-tasking with other jobs. Or was I avoiding a big job I didn't want to do by finding small jobs to do? Anyway, ultimately I was planning to repaint the whole engine bay so I had chosen to give the whole area a good clean rather than only focus on the underside of the tusks.

Years of grease and dirt to be removed

 That's where the time went, but at least it's an investment for the next stage.

Cleaning the 'tusks'

I'd started cleaning everything back in mid February and it wasn't until late March that I was ready to paint the underside.

Under the footwell

As with the rest of the underside, after degreasing, the area got a first coat of epoxy primer. Once it had dried, it was seam-sealed. And when that was dry, it then got a second coat of epoxy.

All shiny now

Perhaps now I can concentrate on painting the rest of engine bay and look forward to dropping the engine back in. That's a big job. I'm sure I can think of something else to do instead before then.

Removing Underseal From The Underside Of The Chassis (Part Three)

Well, a lot of progress in the last three weeks. I managed to......

......strip the underseal from the boot area.

At the moment I have decided not to strip and repaint the chassis around the rear suspension area. I might do that later this year, but was saving it as a winter 2023 job. 

 

With the underise stripped of the leathery underseal, I then went over the whole area (except the engine bay area) with a wire wheel to remove the sticky residue. 

A bare surface at last

A downside of using a high speed wire disc is that it polishes the surface meaning that any paint may have trouble adhering. Last year I'd bought a cheap 'Parkside' brand variable speed angle grinder from Lidl. At the time I just shoved it in the back of a cupboard and forgot about it. Now it came into it's own. I ran a flap disc at very low speed all over the underside. The low speed meant that the flap disc gently scratched the surface to roughen it, without the risk of the disc cutting deeply. I similarly used a mini flap disc on an air tool to get into awkward corners.

 

I vacuumed the surface to remove any clinging dust, degreased and treated any remaining surface rust with dilute phosphoric acid. It's the active ingredient in potions such as Jenolite. Nasty stuff when working upside down! Goggles and gloves are essential - and even then you need to be particularly careful.

The rust treatment converts and turns rust black

Before rust treatment

After rust treatment

I degreased  and vacuumed again and (having plugged all the threaded holes), applied a first coat of two part epoxy primer. I bought a 'winter grade' of epoxy, for use at lower temperatures. I applied it with a roller, but also used a small brush to work it into joins and corners. Brushes and rollers need to be considered as 'sacrificial' as it's not worth the effort in trying to clean them for re-use. I also bought roller tray liners and white 'paper' disposable overalls.

That's better!

Although a roller produces a stippled effect, as it's the underside and will be covered in a waterproof underseal, I wasn't too concerned. Once the first coat was dry, I then applied seam sealer over all the joins.

Seam sealer  over the joins - it 'skins' very quickly

More seam sealer....

The seam sealer is messy, sticky stuff and 'skins' very quickly. Although I used a brush to apply it, it soon began to dry and clog the bristles. Again, I'm not to bothered about neatness here as it's the underside.

 

Once the seam-sealer was dry I applied a second coat of epoxy and am thinking about a third! Phew! Not bad going considering it's winter.

Removing Underseal From The Underside Of The Chassis (Part Two)

More of the same really. And there may even be a 'Part Three'!

As you will realise, my car is up on axle stands at the moment. I wanted the car jacked up high in anticipation of needing to get under it. But I didn't want to jack the car up one corner at a time and twist or destabilise the chassis. 

Up high

I used a single wooden beam across the width of the rear end, to jack the car up from a central point.

Rather than that beam put pressure on floor of the car, I fixed pads to each end that aligned to the square reinforcing pads on the chassis - just in front of the rear wheel arches. To give the car the height I wanted I just slipped my axle stands under the beam and pads. Easy!

Jack and beam under the rear suspension

Except that when it came to scraping the underside of the car where the torsion bar is, that beam and the jacks were now in the way.....Using another jack beam just behind the first beam, I was able to lift the cart and free the axle stands. This time I've relocated the axle stands to the rear swinging arms - giving me better access to scrape the boot floor. The 'cups' of the axle stands sit nicely at the ends of the arms and nestled against the axles - so are not going to slip off. 

Relocated axle stand

As I lowered my jack the arms, of course, moved up until the bump stops bottomed-out, so I needed to raise my axle stands on bricks to give me enough scraping room underneath. I wasn't very happy about using bricks, so used some tyre and scraps of wood to make a 'safety cushion' at the rear end: if the car fell off it's jacks, it would be (part) propped up by the tyre stack.

Tyres under the boot floor for added safety

Scraping was pretty much as before. Again I found areas where the underseal came off relatively easily in big, long, satisfying curls, and other areas where it came off only in stubborn little flakes that got everywhere.

There is a lot of time to think when doing this job and I found myself studying the underside of the car. There are lots of holes on the underside. the ones under the fuel tanks are lflanged around the edges and eft unplugged - perhaps to allow air to circulate or moisture to drain out - although there are also crescent shaped vents under the tank area? I found a couple of different style of bungs elsewhere: there were flat rubber plugs/ grommets with a reinforcing 'X' on the back covering large holes under the torsion bar area......

These are also used to cover glass adjustment tracks in the doors, and the the greasing points in the wheel arches - areas where you insert a tool so that may account for a couple of the bungs under the torsion bar. Though not all four lined-up. This type of bung is also found in the rear face of the boot behind the rear lights. Nothing to do with greasing or adjusting when used there though?

I also found larger, spongey bungs that look like doughnuts with a conical tip - under the fuel tank area. I'm assuming that at least some of these holes are something to do with allowing spot-welder access when the cars were assembled, or maybe holding panels in a jig, but I don't really know.

Bungs and grommets in the floor

The parts book for my car says there are twelve bungs of the same design in the boot floor - part DS.744-129. These are the 'doughnut' ones. They seem to perish and go spongey and sticky. You sometimes mysteriously find the doughnut 'head' under your car when they perished and fall off.

Perished bungs

While the Citroen catalogue says there are twelve of these plugs, the Franzose website says only five are needed for a car. 

Floor sealing plugs

I can account for eleven: seven under the torsion bar box, one under the fuel tank box, three under the front footwell. I'm still hunting for the hole for the twelfth one. I also found four other holes - telltale signs of a towbar having been fitted to the car in past years. At least they had had grommets put in them.

Towbar mounting holes?

Interestingly, the area of floor around the the hole and closing piece for the rear light cable had surface rust underneath it in a very regular shape. It looked as though it had been masked off while the rest of the chassis was dipped or painted to protect it? I'm not really sure?

Unprotected area around the light cable tube?

There were some other details to work around which were fiddly but, as before, this was just the first pass to get the majority of stuff off. I will go over it with a 3M abrasive pad on an air tool and a wire brush on a drill to clean out corners and joints.

I've still got the boot floor/ rear suspension area to do AND the engine bay/ front tusks....

Removing Underseal From The Underside Of The Chassis

I finally got round to starting (that's 'starting', not 'completing') a job I've been putting off for ages: scraping the underseal off the floor of the car. 

Underseal removed from the underside of the car

As part of the prep. for replacing the outer sills, I had tided the inner sills/ box sections - which meant scraping some underseal from the sill/ floor join area. Rather than just underseal those areas again, I felt I needed to go all the way and scrape the whole floor area, de-rust and apply paint. before re-applying underseal in one uniform coat over the whole area. (So, another of those small jobs that grows and grows.....).

Replacing the outer sills

Overall, the underseal didn't look that bad, but there were tell-tale signs of it lifting - mostly on joins and corners. When it lifts, it traps water and that can lead to rusting unseen beneath the underseal. I already had signs of rust along the edges of the reinforcing strips along the length of the sills.....

 .......and around the seatbelt mounting points. Also, on closer inspection, there were other signs of bubbling on the floor pan  and so I wanted to investigate for peace of mind.

 The car was properly supported on four proper axle stands and what had been putting me off was the hours of back breaking working lying on the floor with the car only about 50cm off the ground. The underseal is bitumen based and so quite rubbery. You have to put quite a lot of effort to get beneath the surface to lift it. Originally I crawled under the car on a padded dolly, but found that when I applied pressure to the scraper - the dolly moved backwards! That didn't work!

Entering Limbo Land

I started on the floor pan beneath the rear passenger area and attacked it with a gasket scraper that I had sharpened. Some technique was needed but I found that with the scraper at just the right angle and my elbow wedged on the ground, the underseal came off in long, satisfying,  leather-y curls. I had to frequently re-sharpen the scraper. Occasionally it's edge dug into the metal where the strengthening ribs were pressed. Not enough to make a hole, but enough to stop me in my tracks and waste my energies. Cleaning around those pressed ribs was fiddly and time-consuming.

Working around the 'ribs'

I moved on to the area beneath the front passenger area. That proved to be areal slog..... Whereas the underseal had previously come off in curls. THIS STUFF DID NOT WANT TO BUDGE. It was far harder and even with considerable effort, only came off very reluctantly in tiny, dry flakes. The flakes splinted off in shards that got in my eyes, mouth and nose. I don't know if this difference is due to proximity to the engine and engine heat?

Underseal from the back and underseal from the front.
Spot the difference?

Another complication in this area is the domed recess where the front exhaust silencer sits. being domed, I couldn't get my scraper in at the right angle. Even at the time of writing I have not removed the underseal form the dome ends. I'm thinking I will need to use a wire brush on a grinder or drill.

Front floor and silencer recess

I also scraped the underseal from the area under the tank. On the plus side, the underseal was softer and came off the bigger areas in curls again. On the down side, there are pressed ventilation holes in this area so some fiddly detail work was needed.

Under the petrol tank. Actually very happy with what I found!

Although hard work, I think it was a wise move to remove the underseal. I found the floor covered in 'liver spots' of rust. Nothing more serious than surface rust but the start of what could have been a significant problem. Looking at some of the strips of removed underseal, what I found was tiny pin-prick holes on the outside. Almost too small to see and certainly not obvious when hidden away under a car.

Pin prick holes in the underseal........

Those tiny holes tell a different story on the other side of the underseal and you can see where water and rust are starting to get in - the 'liver spots' I found. Given that my car has been off the road for 20 years, all this occurred before 2000. If the car had been used in that time and I'd not bothered to tackle this job, that rust would be much, much worse.

......And the rust forming beneath

Because of the placement of the axle stands, I still have to do the area beneath the rear arm mounts and the boot floor area.

Still to do....

At the front, I still have to do the area beneath the front suspension mounts.

Front 'tusks'

For all my efforts, this is only the start of the 'first pass'. There is a still a sticky patchwork of grey covering the metal. It has the texture of linseed putty. I need to scrape as much of that off as I can with a flat scraper, as I think trying to remove it with an abrasive pad at this stage will soon see the pad clogged up.

Still work to do

I realise that there has been water ingress between the strengthening strips and the floor pan. I think it would be very destructive to remove and replace the strengthening strips based on what I've found - which is a solid floor. My aim is ti neutralise and convert what rust there is, and then seal the edges to prevent any more moisture getting in. 

So what have I learnt so far?

1. My garage floor is very hard

2. I don't want to do this job again

3. The original underseal was applied to bare, unpainted metal

4. That, by and large, it had held up very, very well

5. That it's hard to remove

6. Underseal is only as strong as it's 'weakest link'. It doesn't matter that 90% is good, if 10% fails and allows the car to rot.