Ladies and gents,

I've recently sand blasted and rust-proofed the front suspension components of a 4wd sapphire cosworth. My question is:

Can you powder coat onto the Vactan coating?

http://cgi.ebay.co.uk/VACTAN-RUST-CO...item1c0ff49b17

I believe the powder coating process involves lots of cleaning/rinsing, a chemical etch and then a phosphating coat prior to the powder being applied? Have I effectively completed the phosphating bit already by applying the Vactan? If I powder coat on top how good a "key" will the Vactan give to the Powder above? Should I just throw on 2x coats of red oxide, 2x coats of black spray, waxoyl and be done with it?

Your thoughts please?

Regards,

Alex

 

The powder coating process depends on the material being coated and how good a job they are doing, aluminum for example ideally needs a checmical strip/clean, then wash bath afterwards.
Powder is ace at sticking though, and your surface should be fine, as it's not loose, but will get to around 170C for 15 mins or so, but that shouldn't be a problem.
tabetha

 

Thanks for your response tabetha. I'll make some calls to powder coaters tomorrow to get thier input.

Alex

 

Hello there.

I've been doing powder coating for over 4 years now and can give you some advice.To get a correct finish you will need to have as much bare metal as possible for the powder to cure correctly without starring up.Just re-working a product thats already been powder coated has trouble taking another coat of powder the second time round.

I keep seeing people put 15 minutes for curing.This is so wrong! Yes the cure temputure should be at min of 180c and max of 195c.At these temps you should cure the item for 30mins.Depending on the nature of the powder your using,most will react good to longer is better.Giving the paint a more gloss/metalic look.

Are you doing this at home or using a company?

 

Just to add.

Pre-treatment is used to give the metal a protection coating,so the paint does'nt fall off within a couple of months or chip easily.Skipping this step will result in poor finish and paint problems later on.

 

Thanks for the further information essexRSTSouthend.

I'm doing the front suspension restoration at home with the vehicle on axle stands. I completed the sandblasting and rust proofing (application of Vactan) at my previous employer as I used to work there as an apprentice mechanic. If I was to go with the powder coating it would be with a company.

Technically, there is a 40-80 (guess) micron skin over all of the bare metal. Nothing else; no loose rust, no grease, no dust. Just bare metal and then the Vactan.

Have you ever attempted to powder coat over a "rust eater/proofer" type substance such as Vactan?

Extract from the aforementioned link: "Vactan is a complex mixture of a vinyl acrylic copolymer and tannic acid for the treatment of corroded steel and iron surfaces. Vactan neutralises the corrosion process by converting the rust into a blue black metallo-organic complex which passivates the surface. It then further protects the surface by forming a film with low permeability to water vapour and oxygen. Vactan is self priming and many do not overcoat but for long term protection it is advisable to overcoat with solvent or water based paint."

Do we think this will provide a good "key" for the powder and do we think that the Vactan can withstand 180deg for 30minutes?

Your thoughts would be most appreciated.

Regards,

Alex

 

ill dont see a problem painting over this excisiting layer.As a company is doing this for you,they should take the correct steps to paint it.let them know that substance just in case.They may well give the metal a quick skim over.Yes its possible to paint on mild rust.The finish will show some pin holes and slightly rough finish depending on how bad it is.hope that helps.

 

Also the paint layer should be fine for good key.In powder terms,60 to 90 microns is a good thickness.Powder should key up to 200 microns depending on paint texture.The smoother the exciting paint is the better.ive seen up to 600 microns and aint pretty sight.Hence reason i say 200 is the limit really.company should know what they doing anyway.

 

I put 15 min uteds as this is the speed we ran out track at, powder coating aluminum window frames, we had to do a timed run every morning and enter it into the book with our signature, the temp we kept at 170C, a deviation of more than 6C set off alarms, I know it was bloody hot as I had to run through the fkin thing when bits fell off the jigs, and it was 42 feet long, warmed up nicely when getting out the other side!!
Ace in the winter though just leave the air locks off, would get from 3-4C in factory part to 25C in about 5 minutes!!
tabetha

 

sorry that made me chuckle as i know how you feel when talking about the heat and having to be anywhere near the oven or in it,which not good.we spray so many items.we use a convey system with pretreatment at 55c,dry oven at 160C,cure oven 180,190c.The paint process in all takes about 2 and a half hours.We use different speed settings for different paints and depending on size of the item.The quickest cure we can do is Ten to 15Mins but on rare occasions.

 

Chaps,

Thanks for the additional information. I popped up to see a local powder coaters and I decided not to do it at all! Why? Well, my lower track control arms still have the ball joints crimped in so I can't remove them and didn't want to cook the grease that is inside. The hubs still had the old ABS/hall sensors in place and had already had the new bearings pushed in. Again, don't want to damage any of these. The anti-roll bar still had it's powder coat in good nick in the middle and I didn't fancy sandblasting that all off to then powder coat again. So...I'm rattle can spray painting them all with two coats of red oxide, two coats of black. I'll waxoyl and maybe stonegaurd after to give the top layer "plasticity" that I wanted from the powder coat.

Prior to this visit I did a little more digging regarding my initial question about powder coating onto the Vactan:

I called a company called "Plascoat" who just so happen to be based in my home town of Farnham. I blagged my way through the telephone system and got speaking to one of their technical gurus. He said that powder coats "key" onto epoxy or acrylic based primer/base coats as they are solvent based. Vactan is "a vinyl acrylic copolymer and tannic acid". Well a copolymer is an epoxy as far as I am aware (excuse me if I'm telling a porky here) and it clearly states that it's acrylic based so the chap advised that Vactan should be fine to powder coat on to.

Anyway...