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welding-primer and POR-15 type primer- how to best use when welding rusty floor/rocker areas?

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  • Body / Glass: welding-primer and POR-15 type primer- how to best use when welding rusty floor/rocker areas?

    I'm working on torque boxes and areas under the rockers and floors on my '57 Ghawk.
    Typically, I'd give everything inside the torque boxes a good coat of Bill Hirsch "Miracle Paint' (basically like POR15, combines with the rust, etc...)
    However, I'll be welding in these areas too obviously. So debating about how to approach this and not have bare spots (hidden from my view, under the new floor or rocker panels) after welding.
    Any suggestions?
    Considered swabbing all the areas that will be "hidden" after welding with Miracle Paint, then wire brushing it off just the areas where I'll be welding and hitting those spots with the 3M welding-primer. The welding primer doesn't stick to rusty areas as well, or I'd simply spray everything with that obviously. A real pain, but I can't think of any other way to do it.
    I'll prime all the NEW metal with just the 3M welding-primer of course. No rust to worry about there.
    thanks!

  • #2
    hmmm, no replies. Do any of you even USE welding primer? (or coat the inside of your torque boxes prior to welding new floors on? I know I've seen reference to that in a few posts, but never welding primer).
    My concern is the heat of welding bubbling the "Miracle Paint"/POR-15 paint away and that area been subject to rust over the years.....

    Comment


    • #3
      Having done tons of body work for 25 yrs I am not familiar w/ this term
      "torque boxes"
      so I cannot comment

      Have used weld-thru primer a ton tho, and it is able to take the heat
      If you are talking about painting repaired areas that you can't get to you just do the best you can

      Usually I've got the body off the frame so access is not a problem
      Last edited by tbirdtbird; 12-04-2011, 05:33 PM.
      1947 M5 under restoration
      a bunch of non-Stude stuff

      Comment


      • #4
        Originally posted by tbirdtbird View Post
        Having done tons of body work for 25 yrs I am not familiar w/ this term
        "torque boxes"
        so I cannot comment

        Have used weld-thru primer a ton tho, and it is able to take the heat
        If you are talking about painting repaired areas that you can't get to you just do the best you can

        Usually I've got the body off the frame so access is not a problem
        tb2

        The torque boxes are completely enclosed metal structures that strengthen the structure of K-series cars. They are located under the floors and are a part of them from the firewall to behind the doors. There is no access no matter which way the body sets.

        Here's my 54K on the rotisserie with the boxes at 12 and 6 o'clock. So any rust coating needs to be added prior to welding. I used heavy zinc weldable primer in mine.



        I guess it's picture night

        Bob

        Comment


        • #5
          I have sold high pressure pumps and dispensing equipment for spraying and extruding what we called weldable sealer for sealing floor pans on new vehicles. I have not used weldable primer but I suppose it works in similar fashion. My thoughts are that regardless of your method, the key to preventing future rust is to button up and seal any work you do with a coating that prevents the metal's exposure to oxygen = atmosphere = air.

          I have riveted, screwed, welded, and hammered seams as close together as possible. Used thin epoxy primer to flow into cracks in floors, inner panels, chassis, etc. Then followed up with an under coating material that is not supposed to dry and crack with age. Once that is done...you limit the vehicle's exposure to bad weather and moisture and hope the work out lives you.
          John Clary
          Greer, SC

          SDC member since 1975

          Comment


          • #6
            re: "torque boxes", sorry, I think "hog troughs" is what the Avanti guys call them; simply the three panels that make up a reinforcing "box" under the floors on both side of the K-body Hawks......
            So, once I weld the new floor in over the top of them, they are hidden forever; yet welded so I'll never know how much of my paint bubbled off in there..... but don't want to spray over the rusty areas with the welding-primer either. : - )

            Comment


            • #7
              bsrosell,
              If you are so concerned with rust inside of these torque boxes, I am not sure where the rust causing moisture is going to come from if you totally seal them from the outside, I would do what you outlined. I would POR15/miracle the whole inside, then wirewheel/sand/grind off just the weld surfaces, then use a weldable heavy primer on those surfaces, then weld it all, THEN I would make sure it was completely sealed from the outside of the box, which includes the inside of the firewall/floorpan.

              NOW, if you are really that nervous of this potential rust inside of a sealed box {if you sense a sarcasim, it is not intentional-just being from Cali I cant imagine rust inside of a sealed box even if the sealed box was bare metal inside, but being from Cali I digress} Then I seriously would do as we have just discussed, but then I would drill a few holes from inside the car thru and into the torque boxes and use a can of some kind of spray sealer like an undercoat or similar and use a spray nozzle tip from a can of carb or brake cleaner that has a nozzle tube and I would spray all over inside the box to coat it POST welding. Then I would get some of those small rubber sealing plugs, like what you might find on a brake drum backing plate or on the floor of many trucks for drainage and stick them in the hole under the carpet...done deal, sealed-sealed-and sealed some more.

              Comment


              • #8
                Originally posted by bsrosell View Post
                .... but don't want to spray over the rusty areas with the welding-primer either. : - )
                If you do your homework, cutting, grinding,etc. you will remove all the rust. Even if it means replacing more than just the hog troughs. You don't want to leave any rust. It is all about the prep work.
                John Clary
                Greer, SC

                SDC member since 1975

                Comment


                • #9
                  Sounds like you are welding up essentially a totally enclosed rectangular tube or square tube in a sense. Seems all the rules of "doing something about rust" should be followed, and not seal known rust up inside. Sandblast, or use your air powered needle scaler, an excellent tool BTW, and get rid of as much obvious rust as you can. Then do repeated treatments of Fozz or other equiv phosphoric acid treatment followed by immediately playing a MAPP or Propane flame over the wet phosphoric acid to speed up the chemical reaction, then wipe down with a rag. Keep doing this until no rust comes off on the rag. Now you have removed the gross rust, and converted the fine rust to iron phosphate, which has a sort of galvanized look to it, and which is very very stable. I have a spare Model A frame in my basement which I did this to 15 yrs ago which looks like the day I did it, no new rust. Now you can coat the entire inside with your fav zinc-rich weld-thru primer, I happen to like 3M the best myself. Now you have done about all you can.

                  BTW being a former northern boy from the rust belt ALL steel gets prepped with Fozz in my shop before any paint or coating is applied. In fact before the shop closes up each day all bare steel is Fozzed. I keep it in a spray bottle ready for action.. Older rusted steel no matter where it is or how hard it is to get to is sanded, ground, blasted, or needle scaled or something to remove the gross rust before Fozz treatment. The iron phosphate coating produced is the best substrate there is for applying any type of coating. This method showed up in the metallurgy books at least in the 40s and maybe earlier. My edition of the Metals Handbook is 1948. Generically this process is called 'passivation'. For stainless (which can rust some contrary to popular belief) you use nitric acid or citric acid to passivate.
                  Last edited by tbirdtbird; 12-04-2011, 06:26 PM.
                  1947 M5 under restoration
                  a bunch of non-Stude stuff

                  Comment


                  • #10
                    Another option: get some petal or plastic snap plugs, about 1 1/2" diameter, and a hole saw to suit. Test in a piece of scrap to be sure the hole saw cuts a hole to fit the plugs! Then use your hole saw from below, and cut holes up into the torque boxes, about mid-point of each section. De-burr the holes.

                    Then get hold of one of those air-operated siphon guns, sold as "engine-washing guns". It's wand with a nozzle, and small suction hose that you drop into solvent you are spraying. Get some cheap Tremclad or Rustoleum rust paint, thin it really thin with mineral spirits, and use the washgun in the sawed holes to shoot a whole mess of it into each section of torque box. Try to cover top, bottom and sides. Of course, you can't really see how much coverage you are getting, but you can wave the gun around enough be sure of getting most of it. And the runny paint will splash around, and creep into seams. Be sure to have drip pans to collect what runs out! You could pour the drippings through a paint filter funnel, and use them again if you run short.

                    It may take months to really dry, but the metal will be protected about as well as it can be. Put the snap hole plugs in after a week or so. and seal around their edges with seam sealer.

                    I used this stunt on rocker panels a few times.
                    Gord Richmond, within Weasel range of the Alberta Badlands

                    Comment


                    • #11
                      Great idea Gord, I have actually done just that using drain oil believe it or not. In the old days back east before the days of rustproofing and undercoating the farmers would use drain oil all over the place inside their doors, behind door panels, etc. Makes a hellova mess you have to let it drain for several days after but it sure does work. I'd still apply the weld thru primer first as described and then maybe add the rustoleum or drain oil.
                      1947 M5 under restoration
                      a bunch of non-Stude stuff

                      Comment


                      • #12
                        I dont think he is talking about leaving rust persay, I think he is saying clean the metal and then use the miracle stuff which is a rust converter and converts any rust that may be left anywhere and stops the rusting.

                        All of the paint then plug ideas are good options if you are really serious about stopping future issues.

                        Comment


                        • #13
                          Weld through primer is available in spray cans and is used when new panels are welded together. The main purpose is to replace the zinc that the heat of the welding removes, thus "hopefully" helping with any corrosion issues that may arise due to the welding. I would also recommend use of a body wax or other type of corrosion material after the welding is done. They are available with extra long tubes and a spray head that will coat all the sides of the inner panel.

                          Besides that, "most" of these cars WILL lead a cherished life for the remainder of "their" days.

                          Jim
                          "We can't all be Heroes, Some us just need to stand on the curb and clap as they go by" Will Rogers

                          We will provide the curb for you to stand on and clap!


                          Indy Honor Flight www.IndyHonorFlight.org

                          As of Veterans Day 2017, IHF has flown 2,450 WWII, Korean, and Vietnam Veterans to Washington DC at NO charge! to see
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                          • #14
                            thanks to all; many good ideas to consider and choose from. See photo below for those of you have not seen my recent posts on "current state", and you'll see my problem. I am fortunate in only having to replace the front portion of the floor, BUT, that in turn limits my access to the LONG closed off 'box' that runs all the way back to under the rear seat. I can barely get my shop-vac hose back there, let alone anything to wire-brush or sand with. And we have 4" of snow on the ground, so any additional sand-blasting is done for the year (at my shop anyway)..
                            I really like the idea of cuting some "plug holes", which I can do later when the body is off, and spraying all kinds of the POR-15 type stuff or something similar in there, so anything that got burned away wiill get another chance of being protected. Yes, in California, I know it is hard to imagine what salt has done to these cars in the Rust Belt... Mine WiLL be a pampered 'driven in summer only" car, I just don't want any current rust continuing to eat away from the inside out, even if I have it all sealed up again after MY restoration....
                            Attached Files

                            Comment


                            • #15
                              http://www.eastwood.com/internal-fra...ay-nozzle.html

                              Mike O'Handley
                              Kenmore, Washington
                              hausdok@msn.com
                              Mike O'Handley, Cat Herder Third Class
                              Kenmore, Washington
                              hausdok@msn.com

                              '58 Packard Hawk
                              '05 Subaru Baja Turbo
                              '71 Toyota Crown Coupe
                              '69 Pontiac Firebird
                              (What is it with me and discontinued/orphan cars?)

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