Rust converters, why ?

[sardine]

Anyone use rust converters like Vactan and Fertan ect , what are you using it for and why ?

There is a craze with Narrowboat boat owners at the moment to splash it all over place, under bitumen hull paint and under oxide primer, i know one boat owner who painted his entire hull with it for no real reason, the master craftsmen of this forum all know the oxides in the primer have to be in contact with the steel to have any effect, I say you don't need it if you have wire brushed back to cleanish steel, as far as I can see the only use for it is to stabilise rust if you can't paint it . Slap it on rusty outdoor steelwork or machinery and it seems to do its job for a year or two, no more, i think its base is latex and by no means waterproof, wire wheel and a good oxide primer with no top coat will last double that in my experience.

 

[steveo3002]

ive never really got along with it , maybe drip some into a seam that you cant do any with

paint it on and it goes black and all fixed right? scratch it with a knife and it will still be red rust underneath

see some people paint it over fresh repairs to stop more rust ...dont think even the sellers claim it does anything on clean steel

 

[barracuda816]

I have used it after cleaning as much rust as possible it paint it over the putting then sand it off leaving just a thin layer in the pitting then paint over. Not sure if/ how much it helps

 

[Pigeon_Droppings2]

I use the 1 pack epoxy rust converters...the stuff you leave on. Quite happy with it...seems to work well.

I don't understand the converters that you wash off with water!

 

[Ross365]

I don't put anything under the zinc phosphate primer (which I am wedded to). My own experience is that "intermediate" materials may not be a good thing.

Going back a long time ago, I got a great result using phosphoric acid on an object that was very badly rusted. The object was quite small and after the acid I took it out and.....put in a large beaker of alcohol, washing off any acid which had not turned in to metal phosphate. Then I painted it and it was good for over 30 years outside, summer and winter. That was before I started using zinc phosphates.

 

[charlysays]

I think you're better off using phosphoric acid at about 10%.
Even better is make an acid paste phosphoric or citric with cellulose powder and spread on , cling film over it and leave for two days to completely remove the rust.
I find items painted with 10% phosphoric acid don't rust for a long time in the workshop but as above, I would always thoroughly abrade and degrease the surface so that any products from the acid are only in the craters.

 

[Smallfry]

I do use Fertan as it does actually seem to do some "converting". It also seems to protect as a stand alone coating for a while (manufacturer says six months) but whether it does any good in the long term, who knows. I only use it on vehicle bodywork, but I think there is no point on thick stuff as it will last years even if unpainted.
I also get the metal as clean as I can first, so it does not have a lot to do, then rub down again before painting.
I do notice however, that most products seem to encapsulate rather than convert, and must not be abraded before top coating. If they truly converted the rust, surely it wouldn't matter if most of it was rubbed off ?

Zinc Chromate was better than Zinc Phosphate, but like many other things. Nanny state has banned it.

 

[MetalMonkey]

I've no experience of boats, so speaking from the perspective of vehicles and general steelwork:

Most of the rust treatments use phosphoric acid as an active ingredient.
Where it excels is getting into all the pits, nooks and crannies where you can't mechanically clean the rust off.
A lot of the treatments just include some sort of gelling agent to make application easier.

It works insofar as it will stop the rust from progressing and seal it, but obviously it needs to be followed up with a good coat of something protective like epoxy.
If you have large areas of flaky rust, it isn't going to do a lot, but not much will. It is also not a lot of good over clean steel either.
Phosphoric acid is supposed to form a good surface for primers.

Not sure what oxide primers are being used, but the only ones of much use these days are the zinc rich ones.
Now I know zinc does react with phosphoric acid, I'm not sure on the chemistry of how that effects the adhesion properties of primers though.
I've never had an issue with applying zinc primer over phosphoric treated steel, but then it isn't a scientific test, and I only treat the areas which are badly pitted and clean off as much of the steel as possible to get a good surface for the primer.

Not sure if that was any help really.

 

[JOEPRO]

I have been restoring my own MB Cars for over 20 years.

Any rust converters I have used, and I have at least 6x on the shelf - never last.

As others have said they merely coat over the rust which is still there by definition of using this.

I used a 2k Rustbuster epoxy which included converter that seemed the best of the bad options.

POR 15 using all steps is OK if you must treat a panel with surface rust followed by UV stable top coats or ideally stone chip the Waxoyl.

 

[Morris]

I use phosphoric acid for rust removal, the coating left by it protects metal for a very long time. I always scuff it up before paint.
The overcoat treatments don't fill me with confidence and I seriously doubt that they give long term eradication of the rust.

 

[marlinspike]

I've used Bilt Hamber Hydrate 80 on my car resto. I use it in hard to reach areas after I've removed as much as I can with sanding or wire brush. It's a last resort really. Has worked OK so far but all these products are best used sparingly I reckon. No substitute for rust removal. I certainly wouldn't be slapping it over everything and hoping for the best; more of an option for surface rust really.

 

[fractured]

I used aquasteel or aquarust (can't remember which). I wasn't impressed. You need just enough rust to convert, but not too much. Also it doesn't work on clean steel. So, whenever I have tried to remove rust with a grinder, disc or wire brush, it has a variance from clean steel to deep rust pits. That isn't ideal for the convertor. My experience is it fails within months.

My go-to now is clean as best I can then phosphoric acid solution until i feel i have converted all the rust, clean with IPA, abraded, clean with IPA, then paint with zinc rich primer. Then a top coat to colour it.

I may use any convertor I have left on non- critical stuff, but nothing I want to keep.

 

[Burdekin]

Jenolite aerosol and Bilt Hamber Hydrate 80 both very good. I only use them where access is restricted like chassis rails. I tested on some steel and both provide a good surface to paint over. I spray a couple of coats of rust converter, epoxy primer and then Bilt Hamber Dynax S50. I use the rust converter as I can't do any surface prep and think it bonds well to unprepared steel. Some other rust converters I've tried have been rubbish.

 

[Pigeon_Droppings2]

The dinitrol epoxy converter is excellent but it's crazy expensive these days. I don't have a blaster so my prep is less than ideal .

Some of the zinc rich stuff I've found doesn't stick very well to clean steel...may be I just used a duff brand though.

 

[Barking Mat]

I use the 1 pack epoxy rust converters...the stuff you leave on. Quite happy with it...seems to work well.

I don't understand the converters that you wash off with water!

Agreed, we have a couple of steel boats, made by a very well known boat maker, and we have to follow procedure.

But washing rust inhibitor off, always struck me as odd.

 

[tom-madbiker]

I know this is an old thread but I'm currently trying to develop a rush converter that actually works after being very unimpressed with the ones on sale and is not water based so it dries quickly currently undergoing testing on my old Landy chassis

 

[ajlelectronics]

I know this is an old thread but I'm currently trying to develop a rush converter that actually works after being very unimpressed with the ones on sale and is not water based so it dries quickly currently undergoing testing on my old Landy chassis

The only rust converter that can work is mechanical removal. Even if there were some (apart from electrolysis) method, the resultant surface is still not going to be solid steel or anything like it, so nothing is going to adhere as well as it otherwise would.

 

[not done it yet]

I know this is an old thread but I'm currently trying to develop a rush converter that actually works after being very unimpressed with the ones on sale and is not water based so it dries quickly currently undergoing testing on my old Landy chassis

I would grit blast and paint with my old, original-formula smoothrite - but only if the chassis was sound in the first place.

 

[arther dailey]

still find old diesel sump oil with a little parafin works on chassis/leaf springs

 

[tom-madbiker]

Smoothrite or hammerite are great but I heard they don't make it anymore what's left in the shops is what's left