Undercoat, good or bad?
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Elder User
Joined: Apr 2006
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Undercoat, good or bad?
I want to sand down my frame. Should I undercoat everything or paint it? I've heard bad things about undercoating. I was thinking about undercoating the bed and fenders, etc. Any ideas?
Senior User
Joined: Nov 2004
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From: Vancouver, Canada
Personally, I'm no fan of undercoating (usually some kind of asphalt material) unless there is perfect factory treated metal underneath. If the undercoat doesn't grab the substrate perfectly, all you're doing is providing a thick layer which holds water/dirt/salt up against the metal. Better to really clean the metal and paint over with a super antirust paint like Por15 or Rustcheck or Blue steel or Rust Bullet. Just my 2 cents.
Junior User
Joined: Nov 2005
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Just got done restoring my 1979 ford trailer special.
The other person who said coat it with pors15 was right on.
My body guy had me put pors everywhere I could.
He surely does beleive in it.
Hes been doing body work for 30 years.
The other person who said coat it with pors15 was right on.
My body guy had me put pors everywhere I could.
He surely does beleive in it.
Hes been doing body work for 30 years.
Post Fiend
Joined: Mar 2005
Posts: 8,542
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From: Louisiana
I like por15 myself, but it is alittle expensive, and can break the budget, but there are no exceptions for the quality finish it leaves. I put some on my floor boards and a few other places, and it worked great.
Elder User
Joined: Feb 2005
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I don't like undercoating either. Painting is better....when undercoating starts to fail it becomes something to hold moisture, salt, dirt, etc next to the metal and then the metal starts to rust/corrode...and because the undercoating is thick and still in place then you can't see the problem until you have serious damage. I like por15 too but if it's too expensive then other paints are acceptable...with painting you can wash the underside just like the outside and you can inspect what you have....you'll be able to catch potential problems and correct them before serious damage is done.
Good Luck!
Tracy
Good Luck!
Tracy
Senior User
Joined: Oct 2005
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Like was previously said, rubberized undercoating will hold moisture if not completely sealed. Is it better than bare metal? Absolutely! But... A buddy of mine stripped down his frame on his F-250 about 3 yrs. ago, and brushed POR-15 on it. I just crawled under it the other day, and I was amazed that it looked as good as when it was first done. He paid attention to detail, but boy, did it pay off. I would say it was time and money well spent.
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Senior User
Joined: Mar 2005
Posts: 297
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I just spray fluid film on my underside every fall. It's oily stuff that keeps all the water off. You can paint it first if you want to make it look nice, this stuff will soak into the paint and keep the water/air off the steel. Only downside is that you have to reapply once or twice a year. I buy gallon jugs of it for $60 and spray it on with an air spray thing (the ones they use for undercoating).
http://www.eurekafluidfilm.com/
I like this one because it's mostly lanolin (from sheep).. get it on your hands and it moisturises them ;-)
There are other rust inhibitors like this too.. lps 3 is supposed to be a good one. I've read some reports of various ones used on aircraft.. they use it in the aeronotics and aerospace industries. In fact, wd-40 was design as a rust inhibitor for aerospace but wasn't as good as many others. Especially the newer ones.
Oh, I've been very impressed with this stuff.. it makes the steel look good and seems to pretty much stop all rusting if you keep it applied. Over time it will actually exfoliate flakey rust because it penetrates it and will work it loose.
http://www.eurekafluidfilm.com/
I like this one because it's mostly lanolin (from sheep).. get it on your hands and it moisturises them ;-)
There are other rust inhibitors like this too.. lps 3 is supposed to be a good one. I've read some reports of various ones used on aircraft.. they use it in the aeronotics and aerospace industries. In fact, wd-40 was design as a rust inhibitor for aerospace but wasn't as good as many others. Especially the newer ones.
Oh, I've been very impressed with this stuff.. it makes the steel look good and seems to pretty much stop all rusting if you keep it applied. Over time it will actually exfoliate flakey rust because it penetrates it and will work it loose.
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Senior User
Joined: Mar 2005
Posts: 297
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Hmm, just out of curiosity I was doing some more reading and noticed that this test:
http://www.rustbullet.com/IndTesting/NTS/ASTM_B117.htm
and this test:
http://www.eurekafluidfilm.com/about/testing.html
Should be the same, although I see the rust bullet substituted real sea water.. don't know what affect that has. Interesting results tho.
Ah, found it.. sea water has 2.7% salt content.. they didn't follow the proper procedures it seems.. odd.
http://www.rustbullet.com/IndTesting/NTS/ASTM_B117.htm
and this test:
http://www.eurekafluidfilm.com/about/testing.html
Should be the same, although I see the rust bullet substituted real sea water.. don't know what affect that has. Interesting results tho.
Ah, found it.. sea water has 2.7% salt content.. they didn't follow the proper procedures it seems.. odd.
Senior User
Joined: Jan 2006
Posts: 195
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From: upstate N Y
Well I'm in the Northeast salt rust snow its all here.I'll go as far as to say a bare uncoated car is better than an undercoated one. I spend alot of time under old cars here when the undercoating drys and cracks or sags it actually keeps moisture and salt against the body.It also prevents air from drying oput these same areas.Oil undercoating is popular around here.They actually spray oil onto the under body into the doors fenders hoods everywhere.When you walk by an oil undercoated car you get dirty.When you see a picture of an oil undercoated car you get dirty.But they dont rust!!
Senior User
Joined: Nov 2004
Posts: 445
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From: Vancouver, Canada
Up here in Canada the stuff that Eedvark is talking about is known as 'Rustcheck'. You pay about $200 for the initial application where the crew drills holes into any enclosed body panels (and then puts in plastic plugs). The entire lower half of the vehicle is saturated in the oil. Every year from then on it costs a bit less - (about $150) depending on the size of the vehicle. Rust check was developed for the Ontario aircraft industry (in the 60s I've heard) where there is corrosion between aluminum panels and steel fasteners. The process is messy and you usually have oily drip marks on your driveway for a few weeks or so. But it works very well. One of the side benefits is that all your undercarriage bolts and nuts are a breeze to remove forever.
Had it done years ago on an old Volvo and caused some hilarious problems - as we left the Rustcheck shop, there was a cloud of smoke coming from the manifold/exhaust as the excess oil burnt off. People were honking and waving as they thought we were on fire. Got stopped by the cops too. What a day!
Had it done years ago on an old Volvo and caused some hilarious problems - as we left the Rustcheck shop, there was a cloud of smoke coming from the manifold/exhaust as the excess oil burnt off. People were honking and waving as they thought we were on fire. Got stopped by the cops too. What a day!
Last edited by Mr. Fixit; Apr 9, 2006 at 11:41 AM.
Post Fiend
Joined: May 2004
Posts: 5,277
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From: St George, SC I-95
Everyone will be suprised how good Rustoleum is for the price ($35 per gallon). I like it and it seems to hold up very good on the frame and unside of the bed and cab. Its not as good as POR15 but its also cheap enough to touch up as needed. I bought the professional grade myself but they also sell a cheaper line for about $25 per gallon. Its worth a try....
Senior User
Joined: Jan 2006
Posts: 195
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From: upstate N Y
Mr. Fixit I can tell we are on the same page with that stuff.I have to shower after checking my oil.The stuff is still dripping out of my truck and it was done 3 years ago.LOL They even drilled my doors up by the vent windows.LOL In my gallery you can see the stuff on my grill in some pictures.It just never stops.Put speakers in my doors and found a dead Mammoth encased in oil.The bolts always turn but oil is kinda ruff on shock and spring bushings.Anyway if it ain't a show truck take a paint brush and some old oil to your frame.LOL Then take a shower.
Senior User
Joined: Dec 2003
Posts: 439
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From: Sussex
I used chasis saver when I did the frame off on my 77 F250. I was told it is the direct competition for POR15. It dries hard as a rock. My only advice is not to a paint anything with it that gets direct sunlight because it fades really fast. Other than that I am real happy. It is also cheaper than POR15. About $85/gallon.