I'm in the process of restorying my fiero, and I want to have it last another 28 years. This car is going to be a daily driver, year round, so I want to do my best at protecting it from rust. How much POR15 (or similar product) do you reckon I'd need to give the underside and engine bay atleast 2 coats?

I forgot to ask another question. Is POR worth using if there isn't already rust? The underside is in great shape, but I want to protect it for the future. Would POR be my best bet, or would I be better off using a cheaper undercoating, if all Im looking to do is protect it?

quote Originally posted by kawana: Is POR worth using if there isn't already rust? The underside is in great shape, but I want to protect it for the future. Would POR be my best bet, or would I be better off using a cheaper undercoating, if all Im looking to do is protect it?

I think the POR would only work properly if you sanded or blasted off all the old paint and prepped or etched the bare metal per their directions.

I've painted tons of stuff with POR15 and have been very happy with it but the occasional areas which were not already rusty or bare metal I was careful to remove the old paint from first.

Although por 15 is a great product, its best to use when the surface is clean. Like the guy above stated, make sure its sandblasted and or clean of any loose rust. Minor surface rust and pitting wouldnt/shouldnt harm anything.

I have done the underside of my fiero whit POR15 and after that i used Bitumen Undercoating Motip. Artnr: 000033



I used 1 can of 1L (but dit also the front hood)

I am not a fan of POR-15. I have worked on several cars that had it installed and it pulled off in large chunks due to poor surface prep. It will not stick to any painted surface (says so on the can - I have easily pulled it off paint several times, and completely stripped a cradle that had it with minimal effort), so the surface must be free of paint, then use their etching product to make it stick.

The other issue with the underside of the chassis is all the overlaping metal and seams where water and salt can get to and start rusting. POR-15 can't get into those areas and doesn't do a great job filling/sealing the gaps. For the underside of a daily driver, I would get it undercoated. The coating is normally thick enough to completely cover and seal up most of the seams. It also is normally designed to adhere to a painted surface.

I blasted my frame paint the upper and por'd the lower and I've had to retouch areas multiple times.. it just plain doesn't stick for some reason. I put a lot of work into the project and prepped better than most anyone ever would.. and I'm very disappointed with it.

[This message has been edited by Steel (edited 10-21-2014).]

Have used POR-15 many times and it seems to stick well only on oil free rusted surfaces. It will also stick on primed surfaces but as pointed out doesn't stick over paint or surfaces with any dirt on them. The vapors are highly toxic and if it gets on your skin it is VERY difficult to remove. It also deteriorates quickly when exposed to UV. The substance is an iso-cyanate compound similar to Crazy Glue.
I would say that its good to use only over rusty metal and it can be painted over ONLY while it is still tacky.

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Ive used por was not happy. I used kbs system on my fireo much happier. heres a link to there site.
http://www.kbs-coatings.com/stop-rust-paints.html

I'm very happy with my results with POR-15. No peeling, flaking or any issues. You do need to clearcoat over the parts exposed to sunlight though.

Dave

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