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Old 09-10-2011, 05:00 PM   #1
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To sandblast or grind and POR15

Fellow Streamers,
Shell is detached and elevated. Some serious rust in the rear of '69 27' Overlander around where the black water tank used to be. Will need to replace tank supports as well as some of the lower "straps" that run along the outer edges of the chassis. I have an opportunity to have the frame sandblasted which would clean the metal for welding however, I would like to use POR 15 for the coating after all work is done vs. powdercoating the frame after sandblasting. Is POR 15 still a viable coating for a sandblated frame?

Pro's and Con's?

Thanks All
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Old 09-10-2011, 05:45 PM   #2
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Originally Posted by donmyrick View Post
Fellow Streamers,
Shell is detached and elevated. Some serious rust in the rear of '69 27' Overlander around where the black water tank used to be. Will need to replace tank supports as well as some of the lower "straps" that run along the outer edges of the chassis. I have an opportunity to have the frame sandblasted which would clean the metal for welding however, I would like to use POR 15 for the coating after all work is done vs. powdercoating the frame after sandblasting. Is POR 15 still a viable coating for a sandblated frame?

Pro's and Con's?

Thanks All
Sand blasting, when done properly, has an advantage over grinding, in that grinding won't let you get into those small places, but sand blasting will.

Andy
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Old 09-11-2011, 08:14 AM   #3
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No it needs the rust to bond
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Old 09-11-2011, 08:40 AM   #4
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To remove the rust using sandblasting is a good idea. Plenty of ferric oxide will still remain to bond well with the POR 15. To leave all that surface rust and flaking will only achieve a sloppy looking job and also leaves the possibility of rust being trapped between the flakes to later bleed through. Sand blasting leaves a clean etched surface that gives an excellent bonding surface. If you add any new metal make sure to use Metal Prep and Marine Clean. That is a super important step.
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Old 09-11-2011, 10:02 AM   #5
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If You Sand Blast...

... you must apply POR-15 "Metal Ready" after you sand blast otherwise you will not get a good bonding between the POR-15 and the surface of the sand blasted steel, and the POR-15 will flake off. (Don't ask me how I know this)

Metal Ready requires a liberal, fresh water rinse. Yep, you must spray H20 all over your sand blasted frame. Guess what it looks like when you get done?

Another challenge that comes with using POR-15 is that you must use a POR-15 topcoat. Conventional paints will not adhere to POR-15 (Again, don't ask me how I know this)

This being said, sandblasting is best way to prepare your frame. If you don't want to powdercoat, use a high quality primer (not POR-15).

Remember, POR-15 was invented for people who wanted to "Paint Over Rust" to reduce time and expense of surface preparation.

It is a waste of money to use POR-15 on sandblasted frames (Don't ask me how I know this)
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Old 09-11-2011, 10:17 AM   #6
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This is what TOP posted in my thread asking the same question. From this, I concluded I should just sandblast and paint POR-15 on - no marine prep or metal ready necessary since all the rust and oil will be blasted away. Plus guys that sandblast usually paint also - you can get two birds stoned at once - or something like that.

Here is what the POR-15 directions say about surface prep:

WHAT IS THE BEST SURFACE ON WHICH TO PAINT POR-15?
POR-15 likes rusted surfaces best. Seasoned metal and sandblasted metal are also good. POR-15 does not adhere well to smooth, shiny surfaces, but will adhere well with the use of Marine Clean and Metal Ready preps.

WHAT IS THE “PROPER PREPARATION”?
If you are sandblasting, blow off the lose dust and apply directly over the surface. On all other bare metal or rusted surfaces use the Marine Clean and Metal Ready preps for proper adhesion. Metal Ready It is a rust remover that leaves a zinc phosphate coating on base metal, the perfect pre-primer for POR-15. Areas that have been previously painted should be cleaned with Marine Clean and then lightly scuffed with 400 grit sandpaper. Keep in mind when POR-15 is applied over another coating it will not prevent against rust long term but will serve as a durable, moisture resistant coating. NOTE: New steel is coated with a protective oil finish at the mill. This finish must be removed before using POR-15.
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Old 09-11-2011, 07:31 PM   #7
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Sand blast defiantly! I waisted waaaay to much time using an angle grinder and a wire wheel. Also you wont end up like a pin cushion when those wires fly off!!
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Old 09-26-2011, 04:09 PM   #8
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Sand Blasting is the most accessible option. if you were having a Off body experience you could have the frame acid dipped any & all rust would be holes.

If you do the blasting your self make sure your body is covered & all orifices on your head have protection most important your lungs.

POR15 is a good product BUT! it has NO UV protection any sun light will fade it out in a month or two you will have to clear over it.

NOW Eastwood makes the same stuff with a UV protecting this product I have yet to use.

Rust Paint - Rust Proofing Products - Rust Protection - Corrosion Control - Eastwood

Its a dirty process but rewarding in the end


SR66
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Old 09-26-2011, 05:58 PM   #9
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POR15 is a good product BUT! it has NO UV protection any sun light will fade it out in a month or two
Important thing is to get ALL the nooks and crannies painted - the few areas (Hitch A frame, bumper supports and the axle mounting plates) that will see sunshine can be top-coated with a little prep work - once the heavy work is done...

2007 I put two thick coats of POR semi-gloss black on my frame, and its been exposed to sun ever since. All thats happened is its got a soot layer on top now, still no rust. Kinda looks like Area 51 stealth black now... I like it
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Old 11-03-2011, 03:16 PM   #10
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If using new angle metal in a frame, it will probably have a thin layer of mill slag (thin gray coating), as opposed to, or in addition to oil. Does anyone know if the mill slag can be left on, using POR15?
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Old 11-03-2011, 03:42 PM   #11
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Everything in the POR literature says mechanical abrasion is required on mill coatings - all varieties - from the baked on oil/carbon (light gray) to the chunkier slag leavings.

Their degreaser and metal-ready products work well after sanding & grinding.
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Old 11-04-2011, 06:51 PM   #12
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No you must clean off the mill scale before you por15.
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Old 11-04-2011, 08:48 PM   #13
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Originally Posted by Alumaholic View Post
... Another challenge that comes with using POR-15 is that you must use a POR-15 topcoat. Conventional paints will not adhere to POR-15 (Again, don't ask me how I know this)...
Humm...I've very GOOD luck with standard top coating over POR15!

Re-did my Hensley, sandblasted, prepped and POR'd...followed by a rattle can topcoat...still looks like brand new 2 years later...and it ain't had the easiest life...

On edit...I wire cup brushed my '63 frame last fall and used Eastwood rust coating...very easy and even without a topcoat the bumper and tongue still look fine.
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