Galvanising front and rear subframes

moltuae · #1 8th January 2020, 03:57 PM

I looked into galvanising when I had my subframes replaced a while ago but decided to go with a coating of POR-15 instead.

spannerrash · #2 8th January 2020, 04:29 PM

I really like the idea of galvanising the subframes. I managed to get hold of a pair of very good condition front and rear subframes last year. Both have very little corrosion and are ideal for galvanising.

I managed to get hold of a full set of bushes actually quite easily. The fronts (8 of them) from Audi main dealer and the rears (4 needed but 2 different part numbers) from ECS Tuning in the US. Except to pay good money for them though. I think mine were around £700 for them all.

Removing the old bushes is also a challenge. Especially the front ones as they cannot simply be pushed through. I managed to get hold of the genuine Audi tools for removing the bushes but I still had to do some improvising.

When I get done with my rear suspension refurb in the spring I'll start to look at getting the frames galvanised or some other suitable coating. I want something that involves "dipping" as the frames are hollow and painting the inside would be difficult.

MikkiJayne · #3 8th January 2020, 05:29 PM

Quote:

Originally Posted by spannerrash

I managed to get hold of a full set of bushes actually quite easily. The fronts (8 of them) from Audi main dealer and the rears (4 needed but 2 different part numbers) from ECS Tuning in the US. Except to pay good money for them though. I think mine were around £700 for them all.

You bought the last set then

I know when I asked recently there were three left. Fat lot of use that is!

Ronin · #4 8th January 2020, 07:33 PM

According to my info the pn for the bush is 4D0399415K and its shared between phaeton and found lots of them on ebay?

My plan was to buy the 2 subframes from forum sponsors then get them galvanised and then give it to my mechanic, this would avoid the car being in bits for probably weeks.

spannerrash · #5 8th January 2020, 07:48 PM

These are the 2 subframes I bought as spares. As you can see they are in pretty good condition already. I was in no rush so I held out until I found some that came from a dry climate.

I can't remember where the front one came from but it was somewhere in Europe. The rear came from southern Italy, a nice dry climate.

All the UK ones I looked at seemed pretty rough.

Ronin · #6 8th January 2020, 07:51 PM

Wow thats a good tip, to buy some from a warm country. Those look like they were taken off a 3 year old car or less!

Dezzy · #7 8th January 2020, 08:12 PM

Tread carefully with hot dip galvo, it's hot, really hot and can cause deformation. I'm fairly familiar with the sub frames can from memory they have holes everywhere and that's good as it'll explode if there are any pockets. Also anywhere that is a tight fit before will be tighter after dipping, it's quite a thick coating.
Lastly choose your galveniser wisely, some are rough even for ships, Crediton are OK depending on when they last changed it out as they are a bit agricultural toward the end it can be lumpy and thick.
We would send stuff to Liverpool from Devon

MikkiJayne · #8 8th January 2020, 09:56 PM

Quote:

Originally Posted by Ronin

According to my info the pn for the bush is 4D0399415K and its shared between phaeton and found lots of them on ebay?

Thats the A8 V8 bush. The S8 version is L and I think that's used on various Bentleys too. The A8 V6 bush is F - not sure what else that might be found on, maybe the V6 Phaeton?

The subframe will probably need dipping in something to strip it in the first place to get all the paint off the inside too. Sandblasting won't work for that, and I suspect molten zinc may not respond well to paint. I'm not sure what sort of hellacious paint stripper you'd need to get the factory coating off because its amazingly tough. Except where its rusty

27litres · #9 9th January 2020, 04:18 PM

I'm a fan of POR15 too. I'm planning on painting the '65 Chev frame with it eventually. Very tough and it can be sprayed or brushed depending on preference.
You can also get zinc rich primers such as Galmet, for addition corrosion resistance.

Also not a fan of powder coating. It has one significant flaw, once it chips, it may as well not be there as far as corrosion is concerned!

If you're concerned about the heat, instead of hot dipped galvanising, you could use a sacrificial annode? Works for bridges and ships (and one fancy looking opera house in Sydney).

Ronin · #10 9th January 2020, 08:03 PM

As it happens I once used to work as an apprentice in an aerospace electroplating company and once in a while we would get company's boses mates ask for their jag suspension parts to be cadmium plated.
We would first degrease them, then sand blast, then rinse and then leave in highly concentrated hydrochloric acid for 10 minutes (the stuff was so strong it would go through you if it dripped onto your body) and then it would get plated.
Hot dip galvanising is a totally different process but preparation should be the same.

I rang about for a few quotes and the cheapest I got was £900 for the single front subframe which is nuts!

I will ask my contacts in Poland maybe they can find a place that does it really cheap, but already this idea is starting to look very expensive and long winded.