POR-15 failure...

hungrymonkey said:

I crawled under my 67 last week to hook it up to the tow trailer (long story that is better suited for talk.)

anyways, I noticed that I had some rust poking out on my floorboards. Which is really dissappointing. considering I have two coats of POR-15 applied under there.

I wasnt able to get a good visual on the entire underside. But it is definantly rust.


Anyone else have this happen? it has been on there for about two years or longer. and I probably have less than 2,000 miles on the car.

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At least your toes haven't rusted. (reference to original application story some time ago - that's still one of the funniest stories I've ever read on this forum)

If I recall (and I may not), you didn't use POR-15's cleaner and metal etch, but opted for muriatic (sp?) acid.

Platonic Solid said:

At least your toes haven't rusted. (reference to original application story some time ago - that's still one of the funniest stories I've ever read on this forum)

If I recall (and I may not), you didn't use POR-15's cleaner and metal etch, but opted for muriatic (sp?) acid.

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Isn't muratic acid for masonry, and not metal?

Ozsum2 said:

Isn't muratic acid for masonry, and not metal?

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I have a jug I dilute and use to eat rust off metal parts. Nasty stuff, but does a good job... I actually try to keep it away from my driveway, my dad told me it would eat up asphalt too.

nosaj122081 said:

I have a jug I dilute and use to eat rust off metal parts. Nasty stuff, but does a good job... I actually try to keep it away from my driveway, my dad told me it would eat up asphalt too.

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It is used to clean bricks after laying so they are pretty, and also to etch concrete so that it can be resurfaced. It is alsoo used in swimming pool water chemistry. Anybody know why? Never seen it used on metal, but it would probably eat just about anything. Heck so does coca-cola.

Ozsum2 said:

It is alsoo used in swimming pool water chemistry. Anybody know why?

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Other than cleaning metal this is the other use I do know... I got this jug from my dad, he moved out of his house where he had a hot tub; he used it to neutralize the water after adding chlorine or bromine or whatever base he used to keep the water clean. We used to use it at the pool I lifeguarded at for the same purpose, the old lady that ran the place said if she ever killed anyone she'd just stick them in our barrel of acid and destroy the evidence

I'm a little concerned to hear about your bad POR experience, I was planning on using a similar product by Magnet Paints for the Cougar; they told me at the store that the only surface preparation that needed done was cleaning the loose stuff off and making sure the surface was clean of oil or gunk, no primer or anything.

muriatic acid caused the rust

Ecthing your metal work with Muriatic Acid (Hydrochloric acid) will definately promote corrosion. The salt left behind from eating the rust off (ferric chloride) is very corrosive. It is unlikely that you can removed all of it by rinsing. Phosphorric Acid, on the otherhand, leaves a residue (ferrous phosphate) that protects the metal from corrosion. Phosphoric acid metal prep is cheap and can be bought at Home Depot or Lowes in the paint departments.

degins said:

Ecthing your metal work with Muriatic Acid (Hydrochloric acid) will definately promote corrosion. The salt left behind from eating the rust off (ferric chloride) is very corrosive. It is unlikely that you can removed all of it by rinsing. Phosphorric Acid, on the otherhand, leaves a residue (ferrous phosphate) that protects the metal from corrosion. Phosphoric acid metal prep is cheap and can be bought at Home Depot or Lowes in the paint departments.

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I used some Rustoleum Rust Reformer on my central air drip pan for the condensor. Same as above, just removed loose rust and painted over, so far so good, that was a year ago. It has the viscosity of water, but dries rock hard.

hungrymonkey said:

who used muriatic?

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Sorry, it must have been someone else.

degins said:

Ecthing your metal work with Muriatic Acid (Hydrochloric acid) will definately promote corrosion. The salt left behind from eating the rust off (ferric chloride) is very corrosive. It is unlikely that you can removed all of it by rinsing. Phosphorric Acid, on the otherhand, leaves a residue (ferrous phosphate) that protects the metal from corrosion. Phosphoric acid metal prep is cheap and can be bought at Home Depot or Lowes in the paint departments.

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Good Info. - Thanks. I read about the use of both of these in my welding book, but it didn't offer the info. you posted.

I did a test with muriatc acid some time ago and it did an excellent job of rust removal. rustyspacer2.jpg I haven't used any on the cars yet, and now won't.

hungrymonkey said:

who used muriatic?

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I did... Never had an issue with it, but I am anal about cleaing and prep so after using it I do a real good job cleaning things down. I'm still concerned about the whole POR not working that great situation; the whole premise is that it is Paint Over Rust... Not sure I see a reason to bother with it if I gotta do the same amount of prep as paint.

I have read an article in a magazine called "AutoRestorer" in which a professional restoration shop owner tested Por 15 against "Eastwoods's" Rust Encapsulator and the rust encapsulator out performed Por 15 in long term rust protection.

I'm not sure which part of Oregon you moved to, but if it's anywhere the coast, then that's the problem. I live near the Oregon border in California, and I can tell you this much, rusty cars used to be everywhere before manufacturers started galvanizing body panels. Some people who don't have garages simply cover their cars in a carport and that makes it worse by creating a "rain forest" under the cover and holding the condensation inside.