Recent research re rust treatment

[scooters]

Thought I would share this with you.

As you may or may not know I run a company that specialises in industrial corrosion management and protection.

 

For years industry standard has been to prepare ferrous surfaces for painting by grit blasting to Swedish standard 2.5 this gives a white grainy finish to the steel.

 

Thing is that no one could work out why when repainted thd paint failed within 5 years. I mean, we are not talking about hammerite here, these are highly advanced systems that cost a lot of money and should be good for 20 years plus.

 

Turns out that the problem is caused by the type of blasting used. Abrasive blasting to remove rust forces tiny chloride particles deep into the metal. To the eye the metal looks clean and rust free but it is far from it.

 

The new system we have developed is to blast the surface using soda or artificial plastic soda. This removes the rust and doesn't cause the same embedding as abrasion. The steel doesn't look like it is clean as it is prepared to its natural colour..A sort of graphite. Areas where rust was present will be scarred darker. Once prepared the steel us washed using a chloride neutraliser, dried and then zinc primed. This ensures no surface chlorides are left and none are embedded in the steel. After it is primed then we apply a polyurethane based epoxy followed by a hard top coat. The life span of thus treatment is 20 years.

 

Should the steel be heavily corroded then post light soda blasting a coat of vactan is applied followed by a high build polyurethane epoxy and hard top on that. Sometimes trying to remove all the visible rust can cause you problems and you can be better off utilising the oxidised metal to secure a binding product like vactan.

 

The use of aggressive blasting is also why classic car resto paint jobs can fail quickly.

 

So...If you are going to blast use soda or a plastic gel or apricot stones or walnut shells. Steer clear of glass and oxides and garnet. ..It will drive the chlorides into the metal and they will start corrosion under the paint. Blasting is a lot cheaper if you can use industrial equipment steer well clear of the sealy machines you see advertised in thd magazines. Soda costs us 20 quid for 25 kg and we buy it by the tonne. A wee sealy machine like those advertised can use 25kilis in 10 minutes. It's cheaper to outsource this as to be efficient huge compressors are needed (our smallest is 300cfm)

 

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[mat_the_cat]

That's very interesting - where I used to work they had a shot blasting machine where I would regularly put car bits. That was using steel shot, and the stuff would come out looking great but even parts dry(ish) stored after painting would go rusty. That may be the reason.

[vulgalour]

After seeing numerous build threads where cars have gone rusty and caused grief after blasting I did wonder why, this has cleared that up nicely.

 

Recently, I was told about 'heat stripping' being the next big thing to arrive to remove paint and some corrosion from panels, would you know anything about this?  I'm not sure heat and car body panels are a wise combination and I have no idea how heat can remove corrosion.

[brickwall]

I wish to resurrect this thread and give you the latest automotive research concerning rust proofing.

 

 

So, a while back I was sorting and fashioning a new mud guard for the Range Rover (approx one year ago) and I have made what could be a vital discovery.

 

When I finished making up the new guard - to replace the one that rusted and fell of, I fixed it on the nuts and bolts as usual. I had also used flap discs to clean up the back of the wheel arch to remove all the crust and wished to paint all this as you would expect. Anyway, there is a water trap at the base of the arch where it meats the mudguard and I got the tube and gun with windscreen sealant and filled the gap which is a terrible terrible water trap and rusts so very easily.

When I nearly got to the end it was jamming up, so I gave the gun a massive double-handed  squeeze and the tube exploded!

 

As you may know, this stuff is difficult to wipe off anything and there was a huge blob about the size of my fist on the lower wheel arch. Fuck it - I just got a paint brush and brushed it on to the arch until it started to go off. I then painted the rest of the wheel arch as per usual.

 

Holy rust proofing Batman!!!!!

 

Today I was gonna do some welding in there and stripped back the paint, however when getting to the sealant it was very difficult to remove. Intrigued, i fought to pull some off with a knife and it was a terrible struggle considering it's very vulnerable area. In the areas where i was able to peel it back using both hands the metal underneath was bone dry and very, very shiny. This is a Range Rover classic remember, so I checked the other side which was just painted and it was just as you'd expect - small areas of damp under the paint due to being chipped.

 

 

Thoughts please and ideas how I can further test this discovery.

 

What is this stuff made of? under the arch it feels very much like the factory arch seal stuff on Volvos.

[Parky]

Sounds like it is acting like Vulcanising paint. My grandad used to paint everything with it - even wooden fence posts lasted for yonks with a coat on.

[brickwall]

I'll look into that.

[Parky]

Here's some stuff - quite complicated!

 

http://www.hitek-ltd.co.uk/military_compounds_paints

 

Grandad just brought home loads of toxic chemicals from the Ford factory in Dagenham and mixed them in Marvel milk tins to make this black shiz!

[jonny69]

On the original subject of the thread, where is the chloride coming from out of interest? Not trying to catch you out; genuine question, because surely there aren't (or shouldn't be) any chloride-based substances in glass, oxides or garnet.

[brickwall]

Here's some stuff - quite complicated!

 

http://www.hitek-ltd.co.uk/military_compounds_paints

 

Grandad just brought home loads of toxic chemicals from the Ford factory in Dagenham and mixed them in Marvel milk tins to make this black shiz!

 

 

Thanks for that. Some interesting reading there.

[richardmorris]

With my chemist's hat on, I'll say that corrosion needs air (oxygen), moisture (H2O) and metal (Fe) . remove one of these and you'll stop the metal disappearing before your eyes. Salt doesn't help at all because you end up with hydrochloric acid (weak) which eats into the metal.

[forddeliveryboy]

Probably a Polyurethane sealant - they use it to stick screens in place, I think. Very sticky, remains slightly flexible.

 

http://www.wisegeek.org/what-is-polyurethane-sealant.htm

[brickwall]

Okay then. I'm going to paint the front arch in this stuff and see how it goes. I need to weld the other one anyway.

 

I'm onto a winner I tells ya.