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Truth about rust converters


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#1 Eddie

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Posted 03 June 2006 - 12:44 PM

OK I know a thread below has covered some questions on the rust converter debate but I thought I'd create another one just to get a few thingsstraight.

What I'd like to with the rust converters is do they actually remove the rust or do they just seal over the top so you can paint over? Coz I've used a couple of converters which I found as useless as tits on a bull - they are only ever good for really light surface rust. Even light pitting it seems to struggle with. They barely scratch the surface and underneath the supposed "conditioned" layer it still harbours the rust in all it's glory. I'm not talking about thick rust with heaps of metal loss but even just light pitting - with maybe 0.5 - 1mm of metal thickness loss. Even when applied several times I still find I have to use a grinder anyway coz it check to see how far down the converter did its job and it barely scratches the surface. Underneath the deceiving top "converted" layers lies the rust untouched and going strongly.

I've only used Septone's converter (supercheap) and Repco's/Autobahn's KnH primer/converter which might be the reason why I having problems. How effective has everyone elses products been working? Have you actually checked underneath the converted areas to see if it's done its job or is that all it's supposed to do, create a seal over the rusting areas? Or have your converters actually worked and I've just been buying shit supercheap crap?

My bonnet is back from the strippers now (bare metal) so I need to do something bout it soon. Cheers, Eddie

Edited by Eddie, 03 June 2006 - 12:47 PM.


#2 _Oldn64_

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Posted 03 June 2006 - 12:52 PM

I cannot remember what the product name of teh one I use but it is neither of the two above. What actually happens is a chemical reaction. The thing is we need to look at why rust continues. and the simple reason for this is that it is a pourous oxide. what this means is that once it starts to oxidise there is not protective layer created. this means that the metal underneath it still open to the elements and thsu the process continues.

On most bottles of rust convertor it will state to wet the surface first. thsi in turn allows the water to penetrate the area and "fill" the holes with water. Then by transfering the rust convertor on the water acts as a path to the other areas. this is an important step. without this you will only "treat" the top lay not the whole thing.

Rust convertor does nto fill teh area or fix it exactly. what it does do is take it from rust and converts it to another metal which is non porous. this does not mean it will not still have holes but it means it will be returned toa servicable area.

Cheers

#3 Pete

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Posted 03 June 2006 - 01:35 PM

The trouble is rust typically forms on a car from the inside out, so if the rust is bad enough where converter only changes the top layer then the rust is too deep and will need to be removed further either by cutting out the offending piece to clean steel or grinding it out with an abrasive disc or using a wire wheel etc to get the surface back to an unaffected substrate.

Rust is a nasty enemy, it produces forces which are astounding, Removing it is really the closest thing to a permanent solution, treating the remaining pitting or surrounding areas with a phosphoric acid based converter is another barrier to killing it or preventing it from reforming but its not the complete solution.

I think the best approach to treating rust affected areas is to get the surface where you think it would be treatable, then grind/cut/wirewheel some more then use your rust converter. If the area gets too thin it doesnt matter because the beauty of steel compared to other products is that you can cut out an offending piece and successfully join another piece of steel in its place via welding unlike timber etc.

There is a reason why you can't guarantee rust repairs, its a natural occurence all you can do is try your hardest to prevent it from forming in the first place with coatings and cleaning, OR treating it as thoroughly as possible. It can be a viscious cycle.

Remember majority of car panel steel is only 0.6mm thick, it doesnt leave a lot of material to work with when treating it. The products you have been using aren't inferior as at the end of the day all converters basically only contain phosphuric acid to perform the chemical reaction. (I'm sure the chemists among us will be able to give a definitive explanation)

Problem when working on cars, particularly restoring 20+yr old steel is that there isnt any quick and easy solutions. Keep at it you'll get there all it involves is more work.

#4 smeer

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Posted 03 June 2006 - 01:37 PM

I use this product by Motospray i bought from a place called Sprint Auto Parts. Its called Oxidizer and Rust Converter.
Comes in a shampoo type bottle and It has the viscosity, texture and even bubbles up like shampoo :P.

But, i find it works. I even remove rust on things like screws, clips and other steel bits heaveily rusted by leaving them over night in a jar with a bit of rust remove and enough water to submerge it all.

I don't treat is as the final surface, tho. I convert the rust and sand it off before painting.

How much did it cost you to have your bonnet professionally stripped btw?

#5 Eddie

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Posted 03 June 2006 - 02:34 PM

$80 to strip via the caustic vats style. Then water blast the rest off. It's another $80 to put it in a 'descaler' which I'm told removes all remaing rust (the caustic strip removes all paint but not rust). I may have to go this way depending how successful I am. The trouble is it mainly located on the underside up inside the supporting brace so I can't get wirebrushes/angle grinders in there like I'd like to.

I'll post a few photos of my bonnet and see what you guys reckon I should do. Right now it appears I only have 2 options... 1 is putting it back in the descaler ($80), 2 is try these converters which as you see I am a little suss on. A third option could be that I cut the supporting brace and modify a new one but thats just not gonna happen...

In general the bonnet is in fair condition. A bit of pitting on the underside and a small hole near the front (from rusting on the inside out). This is the area I'm concerned about and want to treat properly.

#6 TerrA LX

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Posted 04 June 2006 - 12:40 AM

To put it simple as stated, if you cant get to the affected area with some means of abrasive then converter is only going to do half of the job. as for spending another $80 on the bonnet if it is that inportant to you either remove the brace or save for another bonnet.
Just remember acid is thinner than water so if it is not all flushed away (impossible) it will only corrode (more rust).
Sorry.
Try buying your products from a dedicated auto paint supplier.

#7 big chris

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Posted 04 June 2006 - 10:21 AM

Hey Eddie,
The way we were shown how to clean up steel panels at TAFE,
as part of my appreticeship,
This is using a product called "Deoxidine"
Remove any and all loose rust with a rubber backed sanding disc 80 to 150 grit, and wire wheel if needed, then use the deoxidine as per instruction on back of bottle,
This gives a truely clean blued metal finish,
edit
Deoxidine is an acid based product, so glove and eye protection is a good idea.
edit
then apply Prepsol or "wax and grease remover"
Etch prime the steel.
Not sure where you live,
In Brisbane try Queensland Paint Supplies at Salisbury
or Metro Ford Paint Supplies,
should be able to buy some off either place.
QPS might be easier, buy over the counter,
as I think you need an account with metro to order paint and related products.

Deoxidine and the like is not for sale at supercheap or the like as it is a professional type product, but due to poor enforcement of laws in QLD any one can buy it.
Cheers
Chris.

Edited by big chris, 04 June 2006 - 10:22 AM.


#8 FCCOOL

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Posted 04 June 2006 - 10:52 AM

I get my stuff from a dedicated from a dedicated paint supplier and the two I use are concept light rust converter and septone rust converter, the first is like the second but dilluted and ready to use on fresh bare steel, the second I use for heavier rust and pitted areas.
You need to sand of as much rust as possible, a wire wheel or cup brush tends to polish up the top of the rust and if you treat it then sand it again you usually see some more powdery orange rust show up again. If you cant get all the rust of by sanding you need to re apply the undiluted rust converter a few times rinsing and dring it between applications when it starts drying and making a white powdery residue.
rust needs air and water to be mad so anywere that is exposed will rust, if you have light rust under the paint the adhesion will be pretty crap and if it chips or comes of the moisture will spread around the rusty layer underneath and start again. also if you weld a patch in you will have pin holes in the welds, when you apply plastic filler over the weld it will suck moisture through the pin holes and start to form rust under the filler till the filler loses adhesion and starts to seperate. The way around this is to use a smear of fibre glass filler over the welds and apply the plastic filler over the top then seal the back with a rust preventative paint.
some times inside chasis rails or sills or pillars you can not acsess the rust from behind, A comon fix here is to wash it out, blow it out clean it as good as possible, then apply and rinse some por 15 metal ready a few times and paint it out with por 15 rust preventative paint.
on a tighter budget, I have used water based degreaser, then rinsed out with a hose, then sprayed in rust convertor, then hosed out after 20 minutes, then re applied, thena little metho sprayed in to romove moisture, then when completely dry I sprayed out with killrust enamel. with the enamel you cant spray acrylic over the top or it will fry and watch for overspray as this stuff floats around and stays sticky in the air. it seems to hold up pretty good, wipe of the overspray or drips with turps.

When you use rust convertor you need to use rubber or latex gloves so you can save your fingers for sanding, sanding and try not to get it on you, have heaps of clean absorbant rags around.
make sure no sticky residue is left on the metal.
Dont get it on paint primer and bog, it will wreck your bog and the finnish will eventually be completely stuffed.
you need to dry it after you take it of as guick as possible so have a clean dry rag near you.
Any way, gott go use some now myself.

#9 TerrA LX

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Posted 04 June 2006 - 08:31 PM

To put it simple as stated, if you cant get to the affected area with some means of abrasive then converter is only going to do half of the job. as for spending another $80 on the bonnet if it is that inportant to you either remove the brace or save for another bonnet.
Just remember acid is thinner than water so if it is not all flushed away (impossible) it will only corrode (more rust).
Sorry.
Try buying your products from a dedicated auto paint supplier.

Just remember acid is thinner than water so if it is not all flushed away (impossible) it will only corrode (more rust).
Impossible meaning under braces, joints, creases and folds.
Following the instructions of the product you are using is a good indicator of the intended outcome.

Edited by ALX76, 04 June 2006 - 08:33 PM.





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