Rear Trailing Arm- Keeping the rust away

[61Scout]

We all know the perches rust out on the rear trailing arms. In fact, it's common enough that GW sells a repair perch. http://www.gowesty.com/product-details.php?v=&id=23662

I'm reconditioning a trailing arm right now in my shop and I found that a small hole rusted through at the end of the curve. This arm is overall in great shape and from a rust free vehicle. I don't think it's bad enough to require a whole new perch, but I'd like to take some measures to prevent the rust from getting worse.

I was first just going to dig it out and weld it up, but as I did this more and more rust kept piling up. So I felt the underside and can feel the the curve stamped into the arm itself. This is part of the arm, and not the perch piece tacked to the top of the arm. This got me thinking that since rust is present and water undoubtedly got in between the plate and the arm, there would be more rust further up the curve. So I drilled a hole above and sure enough there was rust present. (Green arrow marks the rust through, red arrow marks the hole I drilled)

Now I thought to myself... How far does the rust go? So I drilled a hole near the beginning of the curve and sure enough, there was rust present between the two pieces.

Here's the last picture I where I drilled and installed a sheet metal screw into the top of the perch. The idea was that I could spray some cavity wax down in there. After some further investigation I think I'm going to drill all the way through the re-enforcement channel that sits directly below and then plug weld this (where the screw is now) and then shoot cavity wax up through from the inside up into the spring perch plate that's tacked on.

So here are my questions: First off, does anyone have a picture of the spring perch removed and before welding on a new perch? Second, what treatment would you guys recommend to shoot down the drilled holes to prevent the rust from further development? The space between is very narrow so it has to be something that creeps well. I think an oil would work, but then I have to weld up the holes, and I need something that is going to protect after the welding is done. Alternatively I suppose I could drill out all the spot welds and then re-weld the perch back on, but that is a lot of work and seems unnecessary at this time.

Thoughts? Opinions? Different approach?

-Kevin
_________________
1986 Westfalia Weekender Wolfsburg, RJE 2.3
1985 Tin Top, Subie 2.2 + 5MT
Floppy Mirrors no more: http://www.thesamba.com/vw/forum/viewtopic.php?t=653018&highlight=
Remove the front spindle nut with ease: https://www.thesamba.com/vw/forum/viewtopic.php?t=679567&highlight=
Remove the rear wheel bearing housing without messing with the big 46mm nut: https://www.thesamba.com/vw/forum/viewtopic.php?t=679507&highlight=

-Nec Spe, Nec Metu

[Vanagon Nut]

Seems I went through the same thing digging into the arms I had.
If the perch hat was rusted, the perch obviously needed an R&R.
If perch lifting from arm, same thing.

Here's some pics and notes on what I did

https://picasaweb.google.com/musomuso/1981TrailingArmReplacement

I too wondered of rust prevention on new perch install. I just welded the new
perch all the way around. I did not paint or treat the arm area under new perch.
Wasn't certain this would not interfere with welding process especially since
I chose to weld all the way around new perch.

Clean oil inside of arms. I'm sure it's been done.

Neil.
_________________
1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN

[tpinthepack]

I drilled mine out and pulled the perch off, blasted under it, cleaned up the original perch and plug welded and also welded around the perimeter. Mine are painted now with Glasurit and still look perfect today. Been nearly 4 years. Here is before and after:

_________________
TP in the Pack (I am a cyclist)
1968 Manx N.O.S. w/ Barrett Chassis
1960 Single Cab 1914 w/ 40 DLRA's
1990 Vanagon DOKA
1972 Super Beetle
1979 Super Beetle Convertible
2011 Porsche Cayenne

[Steve M.]

If you already have it off and you do, get it sandblasted and HOT DIPPED GALVANIZED. You will have to remove the bushings before you get it done.

Aside from the sandblasting you have done to it they should be putting it through an acid bath to remove rust before dipping it.
You can go out and buy the spray rod extensions that fit into 80-90% of nooks and crannys for treating with rust preventive chemicals/convertors etc.
IMO, dipping is the only way to know 100% you got every nook and cranny.

If you do not like the hot-dipped shiney appearance it will fade to look like a chain link fence in 6 months or so. Or you can paint it using the "cold-dipped" galvanized out of a spray can as a primer, Krylon sells it as well as a few others mfg's. and paint over the top of that or you can put bedliner on it and that will look good and hold up fairly well.
You can probably use another paint as a primer, but he cold dipped seems to work well over the hot-dipped galvanizing. Any Zinc rich primer would work since that is what hot-dipping is.
You do need to read the can of cold-dipped galvanizing to read what paint you can paint over it.
I tried a few different finishes and wasted some money and ended up doing a Bed Liner paint on it which looks just fine for something you hardly ever see.

[syncrodoka]

Cold galve will rust through if you are covering raw steel.
Hot dip can change the trailing arm bushing diameter and mating surface to the bearing carrier from buildup if the plater is sloppy. It is also difficult to adhere paints to, I hear this all the time from painters trying to paint our ductwork, using different product and resprays aren't uncommon. Hot dip is a great corrosion barrier but even that can be a issue if not done correctly- recheck your plater's work if you have it done.

[61Scout]

Thanks guys. Having those extra pics help. Boy, those galvanized trailing arms look sweet. That would be nice, but a tad outside of the budget on this one. The other trailing arm on this van doesn't even have a hole where the spring popped through. In any case, after giving it some thought I think I'm going to take a different approach and actually enlarge the hole on top where the screw is and thread in a M10. That should give me enough room to direct a spray oil (probably fluid film) into the hat portion of the perch. I can then go around the edges (green circle) and it should spread out towards the outside and down into the curved channel. Then maybe once a year I'll add some more oil. This hole should also be large enough to sneak a borescope in for inspection. At this point I'm only trying to halt the damage. This van doesn't see winter and isn't on the coast, so I feel this approach should work. I guess time will tell, and if it does fail then I'll just buy a replacement perch. Interesting to note, but it doesn't look like the replacement perch has a curved piece for the spring, but rather just a flat piece of steel for the base. Not sure that's so good for the spring, but what do I know. I guess one could add a thicker pad down on the bottom to compensate.

-Kevin
_________________
1986 Westfalia Weekender Wolfsburg, RJE 2.3
1985 Tin Top, Subie 2.2 + 5MT
Floppy Mirrors no more: http://www.thesamba.com/vw/forum/viewtopic.php?t=653018&highlight=
Remove the front spindle nut with ease: https://www.thesamba.com/vw/forum/viewtopic.php?t=679567&highlight=
Remove the rear wheel bearing housing without messing with the big 46mm nut: https://www.thesamba.com/vw/forum/viewtopic.php?t=679507&highlight=

-Nec Spe, Nec Metu

[insyncro]

After freshly prepping and coating the arms, I inject panel adhesive into the nooks and crannies.
3M 8115 will make a water tight seal.

I do not recommend galvanizing, as pointed out, it is a process used for materials that often do not get completely coated.
If your coater is detailed go for it, but I see many better choices.

[Terry Kay]

Have the arms zinc nickel plated, after you have it totally cleaned up.

How you're going to get the inside of the arms totally clean, so any kind of plating to stick is a big mystery.
It will not last on rusted metal, anyway you want to look at it.

Wax on top of rust won't remain either.

You have interior rust?
You're just top coating the garbage.
_________________
T.K.

[Robw_z]

If you watch the video of the Vanagon assembly line, it shows a special computerized robotic arm thing that sprayed these trailing arms, and was controlled by this weird robotic camera-eye thing so it wouldn't miss a spot.

Just had to mention.

-Rob

[Steve M.]

[outcaststudios]

it is 'moot point' (sorry,pet peeve)..i had my trialing arms powder coated in germany and after a few years they are still holding up. normally i dont recommend powder coating as when it chips youre right back where you started and you cant touch it up, but this seems to hold up so far no rust. as far as plating goes having them galvanized defineitly seems like the best long term option, i had the chassis for my citroen hot dipped and its still rust free after a decade.
_________________
'88Doka JX td
'69 westy
(rip)couple bugs
(rip)three type III"s
(rip) '81 vanagon
a bunch of french stuff,and 9 motorcycles.

https://www.thesamba.com/vw/classifieds/detail.php?id=2573791

[Terry Kay]

Zinc - nickel lasts the longest in a constant salt bath vs, straight zinc.

How do I know?

My best friend is this countries biggest zinc, zinc chromate, zinc nickel plant, he can plate an entire car if so need be in his King Kong tank.

He has his lab testing salt spray longevity on parts that have been plated.

Anything as big as those arms are plated on a rack line.

Acid dipped rinsed , plated in whatever procesd, rinsed, dried, & shipped.

I've mentioned this zinc thing before.
Prior to anyone expecting the plating to work the metal Must be clean & rust free, inside &
out or the plating will not stick.
Especially inside them arms that you cannot see.

So, unless you have soaked them arms in some sort of backyard electrolytic bath for a month to get all of the garbage out of its interior entirety, there surely isn't any point to get it plated.
_________________
T.K.

[Sodo]

Zinc (galvanize) protects steel that it's electrically bonded to because its more active than steel and thus sacrifices itself. Once the zinc is gone then the steel can rust. Zinc can do a double-duty to protect steel when it completely encapsulates the steel but it doesn't have to. You will get significant protection even if you can't galvanize the inside. I wouldn't want sloppy galvanizing (dipped) would be a good thing inside the bores for the rubber bushings.

Those perches are rusting because they are galvanically 'sacrificing' their steel selves to save another less-active steel component, either the spring or the trailing arm. There is an electrolyte captured between them (probably salty water from winter driving) that is required to facilitate this corrosion action.

The spring perches need:

1) to be 'ventilated' with more drain holes so the electrolyte drains away and dries up or can be rinsed out by clean water.

or better,

2) to be completely and reliably sealed so electrolyte cannot get captured between the parts. A slightly flexible sealant, or sealed by welding, as long as either method does not result in a cavity that can capture and hold an electrolyte. It can be made worse by sealing a cavity. Hard to know. If you have that perch off, and completely filled with a sealant you can exclude the possibility of water.

and only theoretically just for the corrosion discussion:::: if you have 10 years to observe this::: but #2 above is prob better:::::

3) perhaps a ground strap from the trailing arm across the insulating bushings to the vanagon body. I suspect the parking brake cables are allowing electron travel from a location far away (+ further victim) to this corrosion system that results in the perch sacrificing itself. Are the springs electrically insulated from the Van body at top?
_________________


'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[Steve M.]

Guys, the U.S Navy testing for corrosion treatment estimates the galvanized treatment should be good for 70 years...you figure they might know something about corrosion!
Though there have been improvements in the methods of applying the galvanization since hot-dipping was invented that's long after we're gone from this point on so I'm not really too worried about my trailing arms! these will outlast me.

The one thing that sounds better is the electronic galvanization application just because I'm guessing that it might create less heat. But I haven't done any research on it to know. That would reduce the chance of warping the arms, but when I did mine they measured out to be the same on the jig I made before dipping them.
Dipping it completely as far as I'm concerned definitely gets into all the spaces.
Powder coating did not reach down into the inside of the arms even though the guy tried to get paint in them. The electric attraction just didn't pull it in as hoped.

[bluebus86]

ground strap or not she will rust if water specially salt water gets in contact with the bare metal.

one solution is to weld it all around to exclude water and salt. this should be done after dissasembly and cleaning as all old contaminates and rust must be removed first. use of weld thru coatings would be icing on the cake.


if galvenized, you still have issues of trapped water and salt between the parts unless you have them sealed up. a nice thick hot dipped coating will help seal the seam to limit water engress. again this is best done on cleaned (ie dissasembled and rewelded) prepairskeep in mind that what ever you use to seal the metal,part seams may eventually crack and allow contamination. welding all around is probably the best bet for long term sealing between the parts.


frequent app.ication of undercoating wax type stuff is also helpful, but it is not a long term thing and hence requires periodic recoating.

good luck with the rust repairs
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[Sodo]

Steve your trailing arms will last a long time, and the galvanizing will also protect all the nearby components they are electrically connected to, for example the parking brake cables and rear brake parts. Have you noticed any 'additional benefits'? I would guess, that with galvanized trailing arms, the zinc plating on your e-brake cables won't have to deplete itself truing to protect the trailing arms. If you put ground straps to the van body the trailing arms may protect the van body too. Probably for many years.

For someone who has their arms completely disassembled off the van it has to be beneficial. Regarding warpage, is the trailing arm stamped of cold-formed steel or hot-formed steel? The trailing arm is a complex weldment that could have residual stresses, especially if cold-formed. Hot dip galvanizing is dipping the trailing arm into a tank of molten zinc, certainly the arm reaches 840˚F Stuff can happen starting around 400˚F, and steel softens at 1200˚F. Maybe it warps, maybe it doesn't. Perhaps only slightly and is easily adjusted out in the alignment process.

I suspect there are very good methods to make the stuff last 30 more years while the arm is still bolted to the van. How far you want to go on this may depend what environment the van will be driven or stored.
_________________


'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[Terry Kay]

I don't know where your professional expert plating information is coming from,
But stand firm and read this again;

Any type of electrolytical plating will Not Hang On Rust.
And that is with a big period.
Nyet.
Won't happen.

The rotting of them arms in it's interior has zero to do with them being not grounded.

It's plain & real simple injestation of wheel wash, and poor draining of whatever is thrown inside of them.

Very easy to understand.

If they were plated or coated with something since new, there wouldn't be any problems.

A simple dip in black enamel just don't make for long term durability.
_________________
T.K.

[insyncro]

Get cast trailing arms if you want bomber.

[Terry Kay]

Perfect.

Solid cast iron trailing arms.
Sure won't rust from the inside out.
Bullet proof.
_________________
T.K.

[Vanagon Nut]

I painted the repaired area with Tremclad. Personally, I think my rebuilt trailing arms will last longer than me.


There's no doubt that they get rusty on the inside; in spite of all the greezy
crap I found on the inside, there was rust under that.

The rust starting at the perches seems to start under perches.

Neil.

arm I replaced

_________________
1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN