DIY Rustproofing experiment: wood tar vs linseed oil vs engine oil

[Gubbtratt1]

Land Cruisers are very good at rusting, especially if you drive on salted roads. The best rustproofing there is is rubberised undercoating, but that can only be applied on brand new vehicles, as it doesn't stop rust, it just protects against salt and water. I decided to try some options for used cars.

There are specialised coatings like fluid film and even paints you supposedly can put straight on rust, but as I don't have any of those I'm not testing them.
I might go buy some fluid film equivalent and some hammerite for a second test if there is interest.

The contestants:

10W40 synthetic engine oil: used engine oil is an easy DIY solution. I used brand new oil though.

Linseed oil: supposedly extremely good at rustproofing. The source of that information is probably 150 years old though, so how does it compare to modern oil?

Wood tar: a lot thicker than the oils, which should make it last longer. Hopefully not thick enough to trap moisture though. Smells fantastic, if it even somewhat works it might be worth using it just to have your cruiser smell like a wooden boat.

The experiment consists of coating painted, bare and rusty sheet metal with each coating.

The rusty piece is real 70 series steel, and is coated on both sides to avoid skewing the results by rusting from the backside.

Those are then put in a tub of very salty and slightly dirty water until we get a result.

I'll be back in a few weeks with the results. Suggestions for more things to try out are welcome.

 

[Gubbtratt1]

I looked up the approximate price of the various coatings:

Engine oil: 5€/l (I believe thicker oils which are better suited for undercoating are cheaper)
Linseed oil: 10€/l
Wood tar: 10€/l

Fluid film: 40€/l (only available in 0.4l spray cans in Finland from my research, seems to be closer to 10€/l in one gallon cans)
Hammerite: 20€/l
Dinitrol (rubberised undercoating): 15€/l

Engine oil is by far the cheapest. I found a scientific reason for linseed oil to be better though: it has much smaller molecules which better penetrates. This advantage won't show up in my test though since it's just flat pieces.

 

[Gubbtratt1]

One week update:

To better simulate realistic circumstances I've decided to have the pieces out of the water for a while. They will be on this rock for at least a few days, but probably until next sunday just to make it easier to keep track.

The rust on the painted parts and the oiled unpainted parts is 100% in the water that hasn't dried off yet. The painted but untreated part has the rust stuck to the paint though, while on the oiled parts it's just floating around in the water.

The bare untreated metal has caught a lot more rust, but it can be removed just by touching it. I'm not sure if it's because they've been submerged or if it's because it hasn't rusted yet and is just much better at catching rust from the rusty piece.

The rusty piece hasn't progressed much, not even the untreated part, but there has appeared a tiny hole in the linseed oil part.

I have found another contestant for test #2: red lead paint, used on boat hulls. It's illegal in Sweden, so it must be good, right? It's a fair bit more expensive at 50€/l, but as it's a paint it should never need reapplying.

 

[Gubbtratt1]

Now that the water has dried off I noticed something interesting: on the painted and bare piece, the engine oil is wet and sticky (as you'd expect plain oil to be), while the linseed oil has formed a dry hard surface. On the rusty piece it's the opposite, the engine oil is dry and the linseed oil is wet and sticky.

 

[Gubbtratt1]

Two weeks update:

The bare metal with linseed oil appears to have started rusting. Hard to tell if the oil actually already has failed or if the loose rust just has stuck to the hard surface though.

The tar is dry to the touch where the layer is on the thinner side. Don't know if that's good or bad yet, but I'm pretty sure it's not hardening based on my previous experiences with tar. I have a can that's been standing without a cap for probably close to a hundred years and it can still be stirred.

I thought about doing some kind of abrasive test before putting them back in the saltwater but I couldn't come up with anything that would be fairly distributed and not way too effective.

 

[Gubbtratt1]

Three weeks update:

A layer of salt has formed over the pieces. There's definitely rust on both the engine oil and linseed oil parts of the bare metal, but the tar is still coping fine. There's no obvious changes on the rusty piece, except the hole in the linseed oil part has gotten bigger.

 

[Malleus]

You should be able to get Corroless where you are. Far superior to anything I've seen yet.

 

[Gubbtratt1]

You should be able to get Corroless where you are. Far superior to anything I've seen yet.

Just from a quick googling it seems like it's not available in Finland. Which exact product have you been using? Anti corrosion primer?

 

[Malleus]

It's not available in the US, as far as I've been able to find.

 

[thelal]

enjoying the tests

 

[John McVicker]

POR-15® High-Performance Vehicle Restoration Products - https://por15.com/?srsltid=AfmBOoq4k_VfX0viXJB65vIx4Q0L92NMJ52qd7fBpvGaFt7cgb9Ynv2H

Over my long career with LandCruisers I’ve had excellent results with Por15 products.

 

[Gubbtratt1]

POR-15® High-Performance Vehicle Restoration Products - https://por15.com/?srsltid=AfmBOoq4k_VfX0viXJB65vIx4Q0L92NMJ52qd7fBpvGaFt7cgb9Ynv2H

Over my long career with LandCruisers I’ve had excellent results with Por15 products.

Not really easy to find in Finland and bloody expensive. I've read great things about it though. If I can find some I'll try it in the next round, along with hammerite, red lead, dinitrol, fluid film and thicker oil (did I forget something?)

 

[Malleus]

Red lead primer was once the gold standard for structural steel here. Now it's radioactive.

 

[Gubbtratt1]

Red lead primer was once the gold standard for structural steel here. Now it's radioactive.

It's illegal in Sweden but not (yet) in Finland. That must mean it's good. Similarly I read on some American forum that Hammerite is much worse than it used to be because xylene got banned. Well, Finnish Hammerite cans says "xylene based" on the side, so I have high expectations.

 

[pb4ugo]

I think your results with linseed oil and regular oil is to be expected. Most folks reapply that product when it's appearance becomes obvious that it needs another coat. It's not like it's a more permanent coating.

As for hammerite, I always figured it was more of a paint that finished with a certain texture. When I used it, it was a rustoleum paint product. Since then I just use a gloss rustoleum.

 

[Gubbtratt1]

Four weeks update, only two and a half days late:

A lot of rust on the oiled and untreated bare parts. The hole in the rusty linseed oil part might also have grown slightly. Tar is still holding up fine, but the salt layer is still there despite quite a bit of rain in the last week.

I think your results with linseed oil and regular oil is to be expected. Most folks reapply that product when it's appearance becomes obvious that it needs another coat. It's not like it's a more permanent coating.

None of the coatings are really permanent. I expected them to last a lot longer than a couple of weeks though. When a car is treated with oil it's usually done once every one or two years, not every one or two weeks.

As for hammerite, I always figured it was more of a paint that finished with a certain texture. When I used it, it was a rustoleum paint product. Since then I just use a gloss rustoleum.

I don't know the exact science but I believe either the xylene or the flakes do something to combat rust. We'll find out when I get around to doing the second test.

 

[Gubbtratt1]

Five weeks update:

Apart from the usual hole in linseed oil on rust getting bigger there hasn't happened too much. The untreated metal is doing interesting things though. The tar is doing great as usual, but the untreated, engine oil and linseed oil parts are rusting in quite different ways. There's loose orange rust on all three, partly because the saltwater is full of rust, but the untreated part has formed a hard black surface and the linseed oil part is partly covered in a kind of plastic brown goop, with similar black surface underneath. The rest of the linseed oil part and the entire engine oil part has the kind of rust you'd expect from untreated metal.

All three tar parts are covered in a hard salt layer and are the only ones to be so. On the bare metal tar part the metal is still completely rust free, but the tar has gotten harder and thinner so I can't cover up the hole I just made to check.

I'm ready to declare the test done with tar as the winner, but I'll keep it going until I've gathered everything for the second test. Genuine fluid film doesn't seem to be available in any hardware stores, so I'll use this product from Motonet that claims to do the same instead.

 

[Gubbtratt1]

Six weeks update:

Despite showing no signs of any oil left the oiled parts are doing different things. Linseed oil has formed a dark hard layer and if you scrape off the loose rust from the motor oil you find pretty healthy steel. The untreated part is the only one that has gotten pitted yet.

The tar is much harder than I would expect, but as opposed to Dinitrol it is very stuck to especially the rusty piece.

I have to go to a boat accessory store to get the red lead, but once I have that aquired I'll start the second test.

 

[LK90]

Six weeks update:View attachment 3904813
Despite showing no signs of any oil left the oiled parts are doing different things. Linseed oil has formed a dark hard layer and if you scrape off the loose rust from the motor oil you find pretty healthy steel. The untreated part is the only one that has gotten pitted yet.

The tar is much harder than I would expect, but as opposed to Dinitrol it is very stuck to especially the rusty piece.

I have to go to a boat accessory store to get the red lead, but once I have that aquired I'll start the second test.

Gubbtratt1,

I havent seen anyone do a test with what youre using, with the exception of used motor oil. The tar is new one, interesting.

Have you heard of, or are able to get RP-342??? its from cosmolinedirect.com. Its essentially a sprayable, cosmoline wax. Its used by the US military to protect different equipment and gear. I have it on a daily driver now and IMO, its fantastic, you dont have to reapply it either, unless you want too, or need to for some reason. Its extremely durable, cant wash or pressure wash it off either. Im in Connecticut, and its held up extremely well on our salty winter roads.

 

[Gubbtratt1]

Gubbtratt1,

I havent seen anyone do a test with what youre using, with the exception of used motor oil. The tar is new one, interesting.

Have you heard of, or are able to get RP-342??? its from cosmolinedirect.com. Its essentially a sprayable, cosmoline wax. Its used by the US military to protect different equipment and gear. I have it on a daily driver now and IMO, its fantastic, you dont have to reapply it either, unless you want too, or need to for some reason. Its extremely durable, cant wash or pressure wash it off either. Im in Connecticut, and its held up extremely well on our salty winter roads.

Rp-342 doesn't seem to be available on my side of the pond, but it's fairly cheap so I could possibly import some.

A mix of tar and linseed oil has traditionally been used to protect both wood and metal, which is why I included them. I was curious what plain wood tar would do, as the terrible rubberised undercoating is mostly mineral tar.

I recently got to read more about fluid film and similar. Apparently they're so great because they're lanolin based. Lanolin is pure wool fat, and I've got sheep, so I wonder if I could make something great by mixing not so pure wool fat with wood tar and some kind of oil? I think that will be my next experiment.