16 replies to this topic

[Adam1275]

Hi 

 

just bought a new genuine heritage subframe for my 1990 mini but before I put it into the car I was wondering what was the best method of protecting it (painting, powder coating etc.) thanks in advance. 

[rally515]

Hot dip Galvanising is the best form of long term protection for anything of mild steel, although with regards to a minis rear subframe being dipped in a vat of molten metal, it's not advised  .

 

Powder coating is good, but after it gets chipped the water sneaks in under the coating, think of it as a wetsuit  .

 

Zinc primer and a good few thick coats of brush on Chassis black will be enough protection, so long as you don't damage the coat jacking it up etc..

 

And it should go without saying that you'll dinitrol the whole underside and subframes of the mini for daily drive amounts of protection.

 

Regular intervals of cleaning the underside of a car from the road muck often go missed, so simply setting yourself to a set amount of "proper" washes should see it lasting a very long time with really minimal effort.

[sonikk4]

Various trains of thought on this

 

Galvanise

Powdercoat

Por15

Paint

[sprite72]

What about using hammerite paint .is it any good

[Stu1961]

Just painted a front subframe using POR15 and to be brutally honest Hammerite is just not in the same league and does not even come remotely close . Despite what most folk say POR15 is not any more difficult to apply than any other paint as long as you are well organised and follow the instructions. The finish is extremely durable and hard and in my opinion better than powder coating which is susceptible to chipping relatively easily (Have had experience of both powder coating and POR15 within the marine industry) 

 

What ever you do I would initially get the subframes shot blasted (New ones included)  this will give you a sound, paint ready surface with no other preparation necessary apart from dusting off. Apply POR15 rust preventative paint first followed by POR15 chassis coat (Two coats of each), It is little on the expensive side but a 1 pint tin of each will do both the subframes and all the main suspension components such as top arms, lower arms, tie rods, rear radius arms and hubs.        

[sprite72]

What is por15 I have never heard of it

[dklawson]

POR-15 is a single component "paint" similar to urethane.  It is intended to treat and protect steel surfaces damaged by rust (POR = Paint Over Rust)  It cures by exposure to moisture in the air.  It is applied with a minimum of 2 coats over prepared metal surfaces.  Unlike powder coat or Hammerite, it is slightly flexible and therefore chip resistant.

 

I have applied POR several times during the past decade.  It is a good coating but it has its limits.  I do not agree with some of Stu's statements above.  POR sticks very well to rough surfaces that provide a "tooth" for it to lock into.  It does not adhere well to smooth, sound metal.  The advice given above to media blast the surface is good, key really.  However, "shot blasting" as such is not what I would recommend as that provides a peened surface that is more like textured/smooth.  A blast with coarse abrasive media will leave a better surface for POR.  Acid etching the surface as described in the application sheets in addition to coarse media blasting will give the best results.  Failure to roughen and etch sound metal can result in POR eventually peeling off of the surface.

 

In general POR is good but you must apply it as described in its instruction sheets.  If you don't prep the surface properly and monitor curing between coats you will not have good results.  Therefore, proper preparation of the surface and application of the coatings involves more time.  However, the results can be worth it when applied correctly.

[sprite72]

I was going to paint my subframe with hammerite paint , is this no good for the job ?

[Stu1961]

Hammerite is easy to use and it would be ok to use but I would have to question it's durability and longevity compared to other previously mentioned methods/media types. Only used Hammerite on car parts once and that was on brackets that secured the fog lights on an Escort I had years ago it fell/peeled off within a few months.

 

PS. Just remembered I used it on a Fiesta fan shroud and that went the same way.   

Edited by Stu1961, 13 December 2014 - 01:15 PM.

[Stu1961]

Hi Paul,

 

I bought mine at a place called Frosts I think they are the main supplier for the UK and they were cheaper than EBay.

 

http://www.frost.co....r15-paints.html

 

Firstly I would have to agree with what Doug has said in his post though after my subframe was blasted the surface was very rough to the touch rather than a peened finish. First two coats were POR15 Rust Preventative Paint, product code P230 I used the  semi-gloss black followed by POR15 Top Coat - Chassis Coat Black, product code P500.

 

I brush painted mine. Both paints brush on very well and it's pretty user friendly in that respect though the Top Coat is slightly thicker but is still easy to apply. For clean up use cellulose/lacquer thinner, white spirit will not touch this stuff. Give the brushes a final clean in hot soapy water and they will be as good as new. The most important bit of advice I can give is follow the instructions regarding intervals between re coating and don't paint straight from the tin I dispensed small quantity's of paint into small baby food jars it worked well for me, I also made sure there were no traces of paint on the tins lip and lid before re fitting the lid on the tin.

 

If you click on the paints I used they are both on the this page (Above link)  it will give you more info scroll down to where it say 'Instructions' open that and there is a downloadable PDF document with all the relevant instruction and tips.

[dklawson]

Stu, if your subframe came back "rough" from blasting, it was probably not shot blasted as mentioned in your first post.  When things are shot blasted the media is typically tiny steel balls (shot).  Shot is very good at knocking off paint and rust without removing the base metal. Abrasive media is more likely to have been used to leave a rough surface.  Regardless, it sounds like where we have had success, we have started with similar surfaces.

 

As a footnote to Stu's last post, it cannot be stressed too much that you must immediately clean POR off everything you accidentally get it on or it will be there forever.  That sort-of includes your skin.  Wear rubber gloves or you will be wearing the POR until you wear off a layer of skin.  As for clean up, lacquer thinner does work a treat but don't use it to thin POR.  POR is already thin and lacquer thinner affects how POR cures.  I don't bother trying to save paint brushes used with POR.  I use disposable boar bristle chip brushes (probably available in the paint department of your DIY center).  Lastly, the cleanliness of the paint can lids is equally important as Stu mentioned.  Once you open POR, make 100% sure the paint can sealing channel and bead on the lid are super clean.  I typically put two layers of Saran (plastic food wrap) on the entrance to the can before fitting the lid.  If you fail to clean everything before fitting the lid you will NEVER get the can open again without cutting its bottom off.

 

I don't know if Frost sells the starter/trial kit of POR.  If they do, it is a must-have for a first trial.  The kit used to come with all the prep chemicals, rubber gloves, a disposable brush, and 1/2 pint of POR (that sounds small but it covers a lot).  POR has a short shelf life once opened so it is often best for DIY people to buy it in the small 1/2 pint cans.   Again... I don't know what Frost sells but in the U.S. I buy POR in "6-packs" where I buy 2 grey, 2 silver, and 2 black.  The different colors allow me to use one color for the base coat and a contrasting color for the second coat to indicate that I have full coverage everywhere.

[Stu1961]

I suspect you may well be right about my subframe Doug, one other thing regarding the paints shelf life once opened that is not stated on the tin but is mentioned in the aforementioned PDF documents is they recommend storing the tin in the fridge. I believe Frosts sell the full range of POR15 products over here though I believe the etch primer is a relatively new product in the UK.

 

Strangely one thing I discovered when cleaning my brushes (Bit of useless information really) and this only occurs with the Rust Preventative Paint and not the Top Coat is that the paint stays suspended in the thinner and doesn't settle to the bottom and if left for a couple off days forms a semi solid mass with the same consistency as jelly.   

[limby2000]

Done my subframes in epoxy mastic 1-2-1 went on a treat, don't need priming, just remove all loose rust if present.hard as nails finish.

[humph]

Have used POR15 myself on a few bits. It goes on well but everything the guys have said about getting back into paint tins and a short shelf life is true, it's a bit of a nightmare that way. I can confirm that Frost do sell the small tins which for the DIYer are an essential.

[Curley]

Just been through the same thing myself. I ended up going for powder coat over zinc - best of both worlds. Cost me £80 which when you consider the price we paid for the new subframe it seemed like a good deal.

Edited by Curley, 17 December 2014 - 06:02 PM.