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MG Midget and Sprite Technical - Rust converters- do they work

Several companies sell "Rust converters" which "convert to a hard black stable compound that is impenetrable to oxygen and moisture".

So do they really work? Do they actually do what is says on the tin? - Needed in sections that are difficult to full clean of surface rust and that cannot be reached later on. i.e. the inside of body cavities that I can get at now before I weld new floor panels in but after that they need to look after themselves!

Guy
Guy Weller

Have tried them all. The best I've seen is Rust Bullet. Used it on floors years ago, they are stiffer and solid after weather exposure. I even dropped a chisel (don't ask ) on the surface and it didn't even scratch! Use long gloves and a well ventilated area. I found it's so
much better than those zinc conversions voodoo potions.
Just my experience. HTH.

AH
ah harad

Guy, most of the rust converters use phosphoric acid as the active ingredient. I used some on the sill panels on my MGA several years ago, the replacements had a bit of surface rust on them when I got them so I wanted to treat it then. The car's still in the shop but so far no sign of any additional corrosion or surface rust in those areas and I do see a bit on some untreated bare metal areas. I wouldn't hesitate to spray some in a cavity, let it cure and then use something like Waxoyl to seal it.
Bill Young

I've tried Jenox, seems to work ok. Always best to brush in rather than spray.
Tarquin

Guy,

I have been using Hydrate 80 from Bilt Hamber - I understand it is not based on acid.
Seems to work well.

After closing up sections they have a very penetrating cavity treatment wax - Dynax S50 - in aerosols with 600mm injection tube.
I think in cavities it's much better than Waxoyl which is thicker and temperature dependant.

(I have no connection with BH).

Richard.
richard boobier

Guy. I kept a brand new bonnet stored for ten years before I used it and by that time it had developed some rust in the front corners. I used "Kurust" and it did,-as promised- convert the rust into a hard black stable compound. It recommends that you protect it by painting ASAP, which I did and so far after two years , so good.
Bernie.
b higginson

Guy

I used Trustan in 1989/90

It has to be on rust to work but then turns the ferrous oxide to ferrous tannate

every rusty surface I treated on Lara about twenty years ago is still "virgin" anywhere that wasn't has the worm breaking through again now, even over zinc based primers

I havent seen Trustan for years though but any substance using tannin should be fine.

No exhortations to paint at once either...
bill sdgpm

Thanks.
I have often used phosphoric acid based solutions for dissolving rust - and if patient and the concentration is correct, it works well. I hadn't realised that this was also the basis for rust "converters"

I would intend later injecting with Waxoyl or similar. But the sequence that I am after is:
a) to get rid of as much surface rust as possible by physical abrasion (sanding etc)
b) paint with something to stabilize the remainder.
c) overpaint with some sort of water protective topcoat
d) treat with Waxoyl

The problem is that at some point in the sequence after the painting I need to weld the floor panels on without simply burning off any earlier treatment. I use weld-through primer along the actual welded flanges but this isn't necessarily the best for coating the rest of the internal surfaces to prevent future rusting.

I am basically talking about the main frame "U" channels that are open for treatment when the floor panels are removed for replacement.

Guy
Guy Weller

Thanks Bill, There is something called Fertan which is tanin-based
Richard - I am using other Bilt-Hamber products and they seem pretty good so will take a look at their Hydrate 80 as well

Guy Weller

I think you can only do your best. Rust convertor, then when it is closed up plenty of waxoil. Do you think you really need an extra coat of paint - especially as after welding the floorpanels on there will be areas of bright steel in the joins?
Tarquin

Here is a completely differant approach called electrolisis...Ive seen several examples and vary impressive, I plan to try it at some point in the future just to do it...its certianly worth looking into, cheap, fast and easy

here is a youtube video on it

http://www.youtube.com/watch?v=-8vT2mdXBs8


Prop
Prop

Hi Prop,
I have done some small items with electrolysis just to see how it worked. Done cheaply, using a battery charger, but it worked pretty well. Not so easy for a full car body though, but it would be fun!

Guy
Guy Weller

Phosphoric acid compounds remove rust, and convert the iron to iron phosphate, or zinc-iron phosphate if they contain zinc. An excellent surface for primer. They turn rust black; I have no idea what this stuff is chemically, but I don't think it's what the "converters" make of it. There was a big to-do about the first development of the converters when they came out, and phosphoric acid has been used forever.

I read about the converters before they were on the market, and scrabbled to find some when it first became available. Seems to me the "converters" do a fine job of changing your money to theirs, and not much else. I've used several brands,including the quite expensive original (Duro??) on rusty, semi-clean, and clean metal. Once painted, the rust came through on the treated sections at the same time as the adjacent untreated.

Electrolysis works great at rust removal, and seems to do a sort of "passivation", making rust development much slower than untreated bits. Especially good on cast iron parts like MC castings, and also low grade rolled steel sections.

FRM
FR Millmore

FRM,
Thanks, but I'm not clear on what you are saying. You say that the phosphoric acid converts to make an excellent surface for primer. But then say that the brands you tried rusted just the same as untreated steel.

Yes, electrolysis works to remove rust but isn't practical for the situation I was asking about.

I have cleaned quite large pieces of steel in a large warmed tray of a phosphoric acid solution which was very effective. But the objective then was to remove rust rather than convert it to a stable compound for painting. But again, it isn't really a practical option for dipping a whole body tub on a DIY set-up at home.

Guy
Guy Weller

At 1st I laughed at the idea of using a swimming pool to do electrolisis for a car body....But you know a little creativity mixed with some basic organisation and several other people that want to do the same with there cars would make a viable option...you can all share the cost, set-up, and work involoved...Id think a dug hole about 4 feet deep, 5 feet wide 7 feet long ...Basically a grave (LOL) then line it with a thick rubberry tarp...couple battry chargers, then when your done, drain the chemical and refill the dirt back into the hole

I have used the Dupi brand of rust converters with mixed results...I really think it comes down to the chemical make up of the metal and the amount of rust, I used it in the trunk and floor pans on the midget with vary good results...(no rust returns yet) But I used it on some pot iron patio lawn furniture and it lasted about a season (4 months)...I wish I could be of more help.

Prop
Prop

Guy-
Sort of my point, and yours too, I think:
The phosphoric acid based things are not the rust converters as some seem to think, but they are excellent prep agents before paint. The iron and/or zinc phosphate is crystalline, and paint sticks really well, and the metal is chemically clean. A major thing is that it reduces "creep" of rust under paint. It converts iron into iron/zinc phosphate.

The "rust converters" which "convert" rust into "a stable black compound" just cause $$ to change hands, near as I can tell. I deliberately cleaned rusty panels on several things to varying degrees, then coated half of each section with "converter", then spray can paint. Couldn't tell where the "converter" was after the rust started coming through. My experiments didn't look like it was worth spending any more money, especially since the stuff seems to go bad on the shelf.

My experience for the situation you have is just to get oil into the box, such that it stays put. Rust itself is very stable once oiled. I've never had any real "Waxoyl", but have used similar wax/oil mixes designed for rustproofing. I thin them a bit with motor oil and spray it in the box. One approach is to block all drain holes and fill the box with thick oil, let it soak a bit, then drain it. The oil saturates any rust and gets in the seams, and the wax helps it stay put. Been doing this ever since I put a floor & sills in a BMW 2002. These have an indestructible rubberish glop over all seams. Water gets in a seam and creeps the length of the car, eating the seam entire. One seam (floor to gbx tunnel)had gotten oil in it at the front by the engine, and it had crept all the way to the rear suspension. That seam was pristine, after I uncovered it by heating the sealer 'til it caught fire, and then cutting it out with a razor sharp woodchisel & mallet! Every other welded seam was missing about 3/4" on each panel. The remains of that car are in my back field 35 years later - the rest of the car has vanished mostly, but my welded & oiled joints are still fine.

FRM
FR Millmore

Found some info:
http://www.gemplers.com/tech/mremovefaq.htm
Relevant quotes:
"Not only does it eliminate existing rust, but it seals out moisture to prevent the possibility of future rust formation and corrosion. Surfaces protected with this primer and an oil based paint resist the effects of weather, sunlight, rain and even salt spray without peeling or cracking as long as the oil based paint is maintained per manufacturer's recommendations."

That'd be just like paint, yes?

"Although you do not have to paint after the Rust Converter application, it is recommended to apply a high quality oil-based paint if the item will be stored outdoors. Surfaces protected with Rust Converter and an oil based paint system resist weather, sunlight, rain and even salt spray without peeling or cracking."

In other words, the paint does the work!

"Q: Can Rust Converter be applied to a non-rusty surface?
A: No. Rust Converter should only be applied to the rusted areas, not the whole surface. After the Rust Converter has completely cured, it is recommended to wipe the surface with a damp cloth to remove all excess Rust Converter before you apply the oil-based paint. Rust Converter will glaze coat the non-rusted areas causing the paint not to adhere to those areas as well. "

If it's clean, don't use it. If it has clean spots, the paint will fall off the spots, which will then rust!

"Yes. Rust Converter must be used within 9 months from the date of purchase. The shelf life applies to the product even if it has not been opened."

It goes away if you don't use it.

FRM
FR Millmore

And a real article.
http://www.alan.net/prgshoptips/rustconv.html
Some are phosphoric acid, but it's a scam. Others contain some phosphoric acid, but it's not the important ingredient. Good for old iron that is all rust, but it still depends on the paint. I'll stick to my wax/oil.

FRM
FR Millmore

Thanks FRM (My apologies, although I knew it once, I forget your name. Too many birthdays syndrome!)

That is helpful. Particularly in drawing the distinction between Phosphoric Acid - which I know works well as a rust dissolver - and the "Converters" of unknown formulation.

Old engine oil is a good system. In the "old days" it was what I, and most people who bothered about resisting the rusting process, used. I always kept old sump oil and then slopped and sprayed it all over the underside of my cars, into box sections, sills etc. every year. Humourists here will say that a leaking rear crank scroll will do the same thing automatically. For some reason which now escapes me the perceived wisdom at the time was to mix creosote with it. Not sure that it did a better job but it certainly smelled strongly when it warmed up! I guess now the H & S lobby would frown on such anti-rusting measures. I don't think you can even buy proper creosote any more!

But thanks for the comments. Sharing information and experience like this is what the BBS is all about. That, and identifying random Spridgety locations from photos.

Guy
Guy Weller

Would like to introduce you to a different rust fighting concept:

http://www.owatrol.uk.com

Scroll down on the left to Owatrol Oil.

Although marketed much as a product to be used on wood, Owatrol has been used by classic car people in Norway for 40+ years, with very good results. Originally a Norwegian product, it is now made in Spain and available in many countries.

Owatrol does not convert the rust, but penetrates it and seals it to stop further rusting. Being oil based Owatrol has its limitations, it can only be combined with oil based primers and paints, so you primarily use it on suspension parts, under the wings, floors and other surfaces that will not be exposed. But it flows into every seam and corner you cannot reach.

I use it on the Midget I am now rebuilding, but have no business connections with it :-)

Tore



Tore

I should perhaps add that good surface preparation is of course vital when you use Owatrol too, whatever the sales talk. I use a wire brush and phosphoric acid to remove all visible rust, then Owatrol, then oil based primer and paint, both mixed with about 10 % Owatrol. Cars prepared this way in the sixties are still looking good.

Tore
Tore

The difficulty for the specific elements that I was asking about is getting rid of "all visible rust" on the insides of sections with limited access. Hence the thought that a rust converter might work. The second point of course is that any oil based treatment used would then burn off or ignite when welding to fit the floor.

There is of course a variety of treatments that can then be applied later - assuming access through drilled holes etc. But what I was after was a treatment that could be applied whilst the sections were open and accessible and then followed up with welding shut.
Guy Weller

wow...your not asking for much

$10, a prist, and a phone line to god?

LOL....(sorry)

Prop
Prop

Prop,
I liked your idea of digging a shallow grave in the garden. But the quantity of Phosphoric acid solution needed to fill it would be quite expensive.
The instructions say to use a plastic container like an ice-cream tub but the ones in the UK are too small even for a Spridget.
Maybe your ice cream tubs from Wallmart are bigger?
Guy Weller

I was introduced to a product called OSPHO in 1967.At that time I owned a marina on a canal leading directly to the Gulf of Mexico.
At dockside there was a gas pump. On the tope where a globe would have been placed there was a steel plate about 8" square, It was rusty. South Marine supplies of Ft Myers rep suggested Ospho. I brushed straight Ospho on the plate (both sides) and it was at least ten years before any rust started to show. I had not painted it.It actually was a grey color somewhat like Zinc plating.
I have continued to use Ospho ever since. It must have at least a rusty patina to work. It will do nothing on clean metal. Do not leave it on too thick but use a wipe to smooth it. Otherwise a hard whitish crust will form and it is hard to smooth out.
Sandy
SANDY SANDERS

This might fit a spridget, not sure how well it would do the inside of box sections though.

http://antique-engines.com/trailer-electrolysis.htm
David Billington

Cool!
You know, there are a lot of foreclosed or abandoned houses with swimming pools....

Electrolysis is pretty much a "line of sight" thing, like plating, so the sacrificial electrode has to be reasonably "visible" to the area treated.

FRM
FR Millmore

I use milk Stone remover, buy it by the gallon at the Countrywide store, about £10 from local farm shop, it is Phosphoric acid, works well for me
MarkDJglos

Mark,
What does it do?

Guy
Guy Weller

FRM ...

That is an awsome idea...I like that, dont even have to clean up the mess, just leave it for the bankers LOL

Prop...Now thats a whole new meaning to "Tarp Money"
Prop

Guy
It does exactly the same as the jenox and the like, needs two coats as it is watery, no jelly, to stick it to the surface, it turns the brown rust to black and where I have bare metal it appears to stop it from rusting. The floor pan and inner cill in the garage have not rusted in five years.

I decant it in to a plastic jar and paint brush it on, could easliy use a garden type sprayer for enclosed panels.

But as it is so cheap, I'm happy to spash it around.

They use it in the dairy industry to clean the milking machines on farms.
MarkDJglos

Sorry Mark,
That sounded abrupt and churlish from me.

What I was meaning is does dissolve rust that can then be washed off, leaving clean metal. Or does it produce the "hard black stable organic coating" suitable as a base for painting. I use Phosphoric acid at (£12/ gallon, but have always used it for items that can be submerged and left for several days. The rust turns black and rinses off, leaving clean steel that then resists further rusting for about 6 months, even if left unprotected.
Your milk machine cleaner sounds like the same stuff. We used to use Hypochlorate solution. The smell of it still brings back memories from 50 years ago!
Guy Weller

No probs Guy, took it at face value, always the problem with BBS's

Sounds like it is the same stuff, just different label on the container. As there is, in my mind anyway!!, an element of food safe, used in food industry, then it made it feel human safe if treat carefully. If you know what I mean!!
MarkDJglos

Last year one of the classic car magazines did an article on this very subject they tried a number of products and procedures.
They found the best to be a mixture of 4 litres of coke cola mixed with 1 litre of Harpic toilet cleaner. This is put in a large plastic container and the parts submerged overnight then washed thoroughly with fresh water.
I have used this method quite a bit and it really does work its cheap as coke costs about 20p for 2 litres (the sort that you would never drink) and Harpic about £1 It fizzes when you put the rusted items in and you can almost see the rust coming off.
After things are dry they suggested using Rustbuster 123 I have used this as well it’s a water based phosphoric acid primer/converter.
It go’s on white like emulsion paint then turns green as it soaks in turning dark brown with a plastic sheen when dry this I have painted with POR15 which gives a very hard surface.
G McDonough

My car has a great deal of frame and body rust on it.
Do you think rust converter such as rustoleum would help?
SB Brecklin

This thread was discussed between 09/11/2009 and 18/11/2009

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.