Announcement

Collapse
No announcement yet.

Preventing rust in an overlap weld joint

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Preventing rust in an overlap weld joint

    When fabricating an assembly with two pieces of metal overlapping each other, what is the proper method of connecting them to reduce or eliminate rusting in the joint. To be specific, if I have two sections of, say 1/8"x6"x6" steel plate that overlap each other by 3"- and, say I want to weld the two parallel pieces together. And, let's say I want to stitch weld the seams, that is, not a continuous weld for the full length of the overlap. What steps do I take to make sure that, after painting the assembly, that I don't get rust coming out of the area of metal between the two plates. Should I paint the steel before welding(and wire brush off the area to be welded? Any insight would be appreciated.
    Last edited by MTBob; 11-20-2010, 12:02 AM.
    MTBob
    ____________________________
    MM 251 w/Spool gun
    MM 135
    Evolution Cut Off saw
    Logan Lathe
    Clausing Mill
    Walker Turner Drill Press

  • #2
    spray some cold galvanizing on the area to be concealed

    The paint dries quickly. Use a flap disk or wire brush to get rid of any spray in the weld zone if you want. Some of it is ruined by the welding heat, but at least you have protection in between the two sheets.

    Comment


    • #3
      Originally posted by MTBob View Post
      When fabricating an assembly with two pieces of metal overlapping each other, what is the proper method of connecting them to reduce or eliminate rusting in the joint. To be specific, if I have two sections of, say 1/8"x6"x6" steel plate that overlap each other by 3"- and, say I want to weld the two parallel pieces together. And, let's say I want to stitch weld the seams, that is, not a continuous weld for the full length of the overlap. What steps do I take to make sure that, after painting the assembly, that I don't get rust coming out of the area of metal between the two plates. Should I paint the steel before welding(and wire brush off the area to be welded? Any insight would be appreciated.
      Bob, what are you making ?
      I like Deafman's idea, also after it's painted you could silicone in between the welds.

      .......... Norm
      www.normsmobilewelding.blogspot.com

      Comment


      • #4
        Immediatly after your welds are cleaned, epoxy paint generously along both edges of your lap weld. The epoxy is a 100% vapor barrier.

        Comment


        • #5
          Lets keep in mind that anything applied to low alloy steel is just a delay on the rust setting in.
          Even epoxy paint will break down over time and let in moisture.

          Lets also keep this relative too. Epoxy paint is just about the best way to easily protect a surface from rust. It will take years for it to degrade but it will still degrade. And that is what needs to be addressed. You will never stop rust. You can only maintain the part/assembly. Depending on the application a new pain job every few years is the best thing, along with realizing that one paint job is not enough.
          Miller Syncrowave 200 W/Radiator 1A & water cooled torch
          Millermatic 252 on the wish list
          Bridgeport Mill W/ 2 axis CNC control
          South bend lathe 10LX40
          K.O. Lee surface grinder 6X18
          Over 20 years as a Machinist Toolmaker
          A TWO CAR garage full of tools and a fridge full of beer
          Auto shades are for rookies
          www.KLStottlemyer.com

          Comment


          • #6
            like Norm says, put some caulking in between your stitches.

            Comment


            • #7
              If you can, get your part electroplated PRIOR to painting, that would be the best. A good cadmium (toxic) or zinc (non toxic) with a yellow chromate converstion coating (top coat, also known as "Type II yellow" in the industry) should suit you for a long long time.

              I plate all of my parts that I weld PRIOR to painting. It just prolongs the rust problem that much longer.

              Comment


              • #8
                Use a weld through primer prior to welding. Generally available at autobody stores.
                Miller Syncrowave 200
                Homemade Water Cooler
                130XP MIG
                Spectrum 375
                60 year old Logan Lathe
                Select Machine and Tool Mill
                More stuff than I can keep track of..

                Comment


                • #9
                  Rhino-liner

                  In farming, they make these big gravity boxes for wagons. The boxes get lowered onto an angle iron frame that is built off of an under-carriage that used to be a big rig before hitting the junk yard. One guy sprayed Rhino-liner all around where the angle-iron contacts the sheet metal and 2 inches out on every side. I thought that was a good idea. Every springtime it would sweat between the sheet metal and the angle-iron and rust would spread out after a few years; and it would never be practical to weld solid on angle-iron to sheet metal. Also, in the spots where the angle iron connects to the under-carriage, this guy welded on fish plates to the frame where he intended to build off of... and then surrounded the whole joint with Rhino-liner.
                  XMT 350 w/ S-75 DXA Feeder
                  and a Bernard 300 gun
                  Optima Pulsing Pendant
                  XR-W wire feeder + Coolmate 4
                  with an XR-W Edge Gun

                  Passport Plus w/Spool Gun
                  Regular Passport

                  Dynasty 200DX
                  Trailblazer 301G w/Freak Box &
                  S-32P volt sensing wire feeder

                  Spectrum 1000 Plasma
                  Spectrum 375 Xtreme Plasma
                  Regular Spectrum 375 Plasma

                  Victor H315FC torch & accessories
                  Victor 100FC torch & accessories
                  Meco torch & accessories by Kent White

                  Comment


                  • #10
                    Also, the auto companies used to have all those rust problems that arose out of overlapped joints that had been spot-welded or otherwise overlapped and had been painted over. Their solution was to run the line down into a submersion dunk tank of electroplated paint after the body was completed in the "Body-In-White" stage. Now, all components (even the frame...if applicable) is submerged in paint. Initially, they still neglected the frame. The bought under-carriage paint in bulk and got the cheapest stuff they could. All they cared about was to get the frame "black" because the customer wouldn't see it anyway.

                    I guess a guy with a weld shop could maintain a sealed tank of highly thinned rustoleum paint in which to submerge parts. Just add more paint and thinner every oncle in a while. It would have to be the size of a parts washer, have an aggitator pump of some kind, and have a gasketed lid so the thinner wouldn't evaporate away.
                    XMT 350 w/ S-75 DXA Feeder
                    and a Bernard 300 gun
                    Optima Pulsing Pendant
                    XR-W wire feeder + Coolmate 4
                    with an XR-W Edge Gun

                    Passport Plus w/Spool Gun
                    Regular Passport

                    Dynasty 200DX
                    Trailblazer 301G w/Freak Box &
                    S-32P volt sensing wire feeder

                    Spectrum 1000 Plasma
                    Spectrum 375 Xtreme Plasma
                    Regular Spectrum 375 Plasma

                    Victor H315FC torch & accessories
                    Victor 100FC torch & accessories
                    Meco torch & accessories by Kent White

                    Comment


                    • #11
                      Don't spray silicone into the joint if there's any possibility that you will want to paint it later . . . .

                      Comment


                      • #12
                        What I have used a lot is a primer called 'Weld Thru Primer.'
                        It is loaded with zinc and you paint the surface of both sides of the plate joint then overlap the plates and weld it up. The primer dries quickly.
                        As the name implies, you can weld through this material and it protects the steel from then on.
                        pg
                        Dynasty 200 DX_set up on 3 phase
                        Coolmate 3
                        MM 251 w/ Spoolmatic 30A
                        HTP 625 Micro Cut Plasma Cutter
                        Victor O/A Rig
                        Bridgeport Mill_3 phase (w/ Acu-Rite 4 axis DRO)
                        10 inch South Bend Lathe_3 phase
                        Baldor Double Cup Tool Grinder_3 phase
                        Baldor 10 inch Buffer
                        Rockwell 12 inch Disc Sander
                        Cyclone 2ft X 3ft Bead Blast Cabinet
                        Quincy 325 2stg- Air Compressor_3 phase
                        Graymills Built-in Parts Washer
                        Rockwell/Delta Planer, HD Shaper, Uni-Saw etc.

                        Comment


                        • #13
                          Originally posted by seattle smitty View Post
                          Don't spray silicone into the joint if there's any possibility that you will want to paint it later . . . .
                          As far as I know you can buy Paintable Silicone sealant .

                          ............ Norm
                          www.normsmobilewelding.blogspot.com

                          Comment


                          • #14
                            Originally posted by nfinch86 View Post
                            As far as I know you can buy Paintable Silicone sealant .

                            ............ Norm
                            if you are painting it with water based house paint it will work....but if you are using oil or mineral based auto or equipment enamel it will cause fish eyes in the paint...... just a little story from when i was doing body work on cars and trucks. another thing you want to stay far away from when you are painting is wd40. as i was shooting a car open air a guy 50 yrs away sprayed a rusty nut with wd40 and the slight breeze drifted it over to where i was working and presto my job was ruined. fish eyes started popping up everywhere.
                            miller 225 bobcat
                            miller aead200le (with miller hf tig trailer mounted)
                            mm175, mm211, TA181i
                            mm252 w/30a spool gun
                            precision tig 225
                            hobart stickmate LX ac/dc
                            Speedglas 9100X & XX / Miller Digital Elite
                            hypertherm 380 & cutmaster 52
                            victor journeyman & super range
                            ridgid chop saw, kalamazoo band saw
                            steel max and evolution carbide saws
                            6 4.5" & a 20lb 9" rockwell grinders
                            case 580 backhoe (for what i can"t lift)
                            if first you don't succeed
                            trash the b#####d

                            Comment


                            • #15
                              Originally posted by piniongear View Post
                              What I have used a lot is a primer called 'Weld Thru Primer.'
                              It is loaded with zinc and you paint the surface of both sides of the plate joint then overlap the plates and weld it up. The primer dries quickly.
                              As the name implies, you can weld through this material and it protects the steel from then on.
                              pg
                              Excellent!

                              That is a revelation.

                              Thanks
                              Nothing welded, Nothing gained

                              Miller Dynasty700DX
                              3 ea. Miller Dynasty350DX
                              Miller Dynasty200DX
                              ThermalArc 400 GTSW
                              MillerMatic350P
                              MillerMatic200 with spoolgun
                              MKCobraMig260
                              Lincoln SP-170T
                              Linde UCC305 (sold 2011)
                              Hypertherm 1250
                              Hypertherm 800
                              PlasmaCam CNC cutter
                              Fadal Toolroom CNC Mill
                              SiberHegner CNC Mill
                              2 ea. Bridgeport
                              LeBlond 15" Lathe
                              Haberle 18" Cold Saw
                              Doringer 14" Cold Saw
                              6 foot x 12 foot Mojave granite

                              Comment

                              Working...
                              X