Underbody Rustproofing

[cancunia]

I'm not doing a lot of miles at the moment, looking underneath the car yesterday I noticed that the suspension arms are getting a bit rusty. It's not normally something I'd notice so am guessing it's to do with the time spent standing outside rather than getting road spray. 
Any thoughts on what to spray or paint with? I've tried stonechip in the past but not really been impressed, same goes for underseal spray.

[notsofast]

I started a thread on this last year, and received a few suggestions - https://www.berlingoforum.com/thread-21583.html

[cancunia]

I started a thread on this last year, and received a few suggestions - https://www.berlingoforum.com/thread-21583.html

Aha, many thanks.

[saskak]

I'm not doing a lot of miles at the moment, looking underneath the car yesterday I noticed that the suspension arms are getting a bit rusty. It's not normally something I'd notice so am guessing it's to do with the time spent standing outside rather than getting road spray. 
Any thoughts on what to spray or paint with? I've tried stonechip in the past but not really been impressed, same goes for underseal spray.

I also had the same idea as there are a few areas on mine that are starting to show a bit of rust, but did not want to spend too much money on sprays. I mean, the CRC heavy duty marine corrosion inhibitor is £60 for a bottle. Fluid film is a bit difficult to get and also expensive. I know there are several youtube channels (projectfarm and others), that have tested a few of these.
I had a little experiment of my own. I got a few pieces of mild steel to bare metal with high strength HCL, not that high as the brick cleaner only goes to ~9.5%.

Most of the fancy sprays have lanolin as the active ingredient and some compounds for physical properties such as hardness/softness, stickiness, solubility, etc. I thought that I could fairly cheaply buy lanolin and have a test of my own. Lanolin is solid at low temperatures, so difficult to spray. I read somewhere that you can mix it with mineral/white spirit and that would be good. The idea being the white spirit evaporates and leaves a uniform coat of lanolin. Petroleum jelly (vaseline) is also quite good at stopping rust, as is generic grease or that is what I read/thought. I had quite a bit of spare CV joint grease from replacing the CV boot.

I had all these applied to 10 pieces of the mild steel and put them outside for 1 year, rain, shine, hail, cold, all. I put it outside last January (2021), so a year now. Here is the list of the tests I did. The Dax is a mistake. The bottle said 100% lanolin, but it is a hair conditioner with some lanolin in it. I bought lanolin (anhydrous) after I realised he dax was not pure lanolin, but used the hair conditioner as well on the tests, as I had already bought it.

1. Dax + Petroleum Jelly
2. Concoction of Lanolin + Petroleum Jelly + Mineral Spirit
3. Dax
4. Lanolin
5. Petroleum Jelly
6. Control (nothing, just the bare steel)
7. Olive oil (what the hell, my wife suggested it)
8. Spare CV joint grease
9. Servisol silicone grease
10. Control (nothing, just the bare steel)
11. One piece of rusty steel with Lanolin
12. Control (rusty steel without anything)

After 1 year (photo taken today), here are the results, these are my takes on them, as a photo is not as good as looking at it. Photo of the steel pieces is attached. Now, these do not take into consideration that the underbody is hit by a lot of water spray, salt, small stones, etc. I just wanted to see which one will stop rust. I have no problem re-applying on problematic areas.

The stuff that did anything against rust were in number order: 1 (Dax+Petroleum Jelly), 3 (Dax), 4 (Lanolin), 5 (Petroleum Jelly) and 9 (Servisol silicone grease).
Photo does not do it justice, but the best of them all was Lanolin on its own, 4 in photo. There is a bit of brownish tarnish on it, but it is not rust. I suspect some oxidising of the Lanolin itself. The rest had some signs of rust.
I put lanolin on rusty steel (11) and it looks the same, the rust has not spread more. Surprisingly this Dax thing works to some extent. The CV grease did nothing, but the Servisol silicone grease had some success preventing rust, not as good as Lanolin or the others. I had it laying around and it is really thick grease. My concoction of mineral spirit, lanolin did not do anything, but maybe I put little lanolin or petroleum jelly and too much mineral spirit. There was a formula online that it was something like 5:1 (5 parts mineral spirit and 1 part lanolin). Maybe more lanolin would work better, but by looking at the result (complete rust coverage) I am not too hopeful. Petroleum Jelly was second best. I did not think about it at the time, but I should have mixed lanolin + petroleum jelly or make combinations of them all, too many combinations and not enough steel pieces :-).

On the photos the undersides are not coated, so there is a little bit of rust coming from underneath on the sides.

My take on all these. If I take a bolt off my car that is somewhat exposed to the elements, I now coat it with lanolin, so it does not rust or at least slows the rust process. I have not yet treated anything bigger.

   

[cancunia]

Wow, many thanks for taking the time to do the tests and post the results.
A bit of searching shows some marine & automotive products anti corrosion using lanolin, but they seem expensive, the cheapest I saw was £17.00 for 500ml. In the mean time, I have a can of Halfords spray grease which from the safety sheet seems to be mostly petroleum jelly.

Is there a particular reason for using anhydrous lanolin as opposed to unrefined?

[saskak]

Wow, many thanks for taking the time to do the tests and post the results.
A bit of searching shows some marine & automotive products anti corrosion using lanolin, but they seem expensive, the cheapest I saw was £17.00 for 500ml. In the mean time, I have a can of Halfords spray grease which from the safety sheet seems to be mostly petroleum jelly.

Is there a particular reason for using anhydrous lanolin as opposed to unrefined?

Petroleum jelly seems to be the second best. There was no particular reason for the anhydrous Lanolin, it was just more convenient to buy it in a 100g bottle and at the time it was £7. There are much cheaper versions, but it was cheaper overall to buy a small jar and not have a huge bottle at home. I did not think it would work, so did not want to spend too much. Granted, my £7 100g bottle is much more expensive, but it was at the time the cheapest option.

[Sol]

That is a great bit of work Saskak. I have had good results paint wise with Finigans smooth-rite as a weatherproof paint on metal but the Lanolin is amazing from your tests.

I think if anyone wanted to paint metal parts under the car and then add lanolin etc, I would try smooth-rite first as the paint of choice. A mate years ago stripped his Suzuki GS550 frame to bare metal in the shed, then painted it with smooth-rite black, and many years later it was still like new. This was a bike that sat outside in all weathers with no covers on it at all as he did not have a garage and also, no car. This was a 365 day a year biker.

[cancunia]

From a bit of further reading, it looks like lanolin is best applied at higher temperatures due to being too viscous otherwise. There are a couple of lanolin based products that I've found from searching around today and will probably get some for applying in warmer weather, in the mean time it'll have to be spray grease which will hopefully have some benefits in the short term.

For future ref, these are the 3 lanolin based products that I found online, they are in no particular order & I have no first hand knowledge about their effectiveness, if there are any more please post them:

Corolan
Lanoshield
Lanoguard

[saskak]

The best still is some sort of galvanisation/electroplating, but only works on small parts that can be taken off.

The turbo shields on my M59 were always rattling, I bought a new one for ~£35 and that one broke in 1 year. I have had enough with these stupid shields and it bothers me that they rattle and produce noise. I had two steel pieces (3mm) and put them in there between the shields after moulding them into shape. Kind of a bridge between the bolts. The shields have not moved/rattled for 3 years now. Because it is a bit of extreme heat there next to the turbo, these rusted in a matter of weeks. A bit usightly when going for an MOT.

I stripped these to bare metal and with an old phone charger made an electroplating Zinc bath, Zinc is pretty cheap to buy. 30min with the voltage from the phone charger had left quite a bit of Zinc on the steel. I put these on the car and it has not rusted one bit since, even with the heat cycle from the engine. That was a year ago. Unfortunately, I cannot strip the whole car and electroplate it, hahaha, getting there though. It works for some pieces that I take off and have the time to electroplate. Here is a video if anyone is interested: https://www.youtube.com/watch?v=ox6EIiIpWOo

I have to make a video for the lanolin, but have not had the time to film the end. I had almost forgotten I had them by the garage, until cancunia had this thread.

[notsofast]

The stuff that did anything against rust were in number order: 1 (Dax+Petroleum Jelly), 3 (Dax), 4 (Lanolin), 5 (Petroleum Jelly) and 9 (Servisol silicone grease).
Photo does not do it justice, but the best of them all was Lanolin on its own, 4 in photo. There is a bit of brownish tarnish on it, but it is not rust. I suspect some oxidising of the Lanolin itself. The rest had some signs of rust.
I put lanolin on rusty steel (11) and it looks the same, the rust has not spread more. Surprisingly this Dax thing works to some extent. The CV grease did nothing, but the Servisol silicone grease had some success preventing rust, not as good as Lanolin or the others. I had it laying around and it is really thick grease. My concoction of mineral spirit, lanolin did not do anything, but maybe I put little lanolin or petroleum jelly and too much mineral spirit. There was a formula online that it was something like 5:1 (5 parts mineral spirit and 1 part lanolin). Maybe more lanolin would work better, but by looking at the result (complete rust coverage) I am not too hopeful. Petroleum Jelly was second best. I did not think about it at the time, but I should have mixed lanolin + petroleum jelly or make combinations of them all, too many combinations and not enough steel pieces :-).

Looks like there's a relationship between effectiveness and viscosity i.e. the more viscous products work better.  Which makes sense - very liquid oils will be removed by weathering.