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Patch Panel Metal
I have to do some sheet metal patching (rust) and as a novice MIG welder, I was wondering what the most appropriate type of mild steel to use is, please? I have seen that some people use galvanized steel and others use untreated steel (cold-rolled?). I recall in my MIG welding lesson, we were warned of the hazard of welding galvanized steel - is it just a case of grinding the weld area thoroughly? Or can a non-galvanized steel be used, along with a rust-preventative paint such as POR-15? Thanks.
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06-03-2014, 01:33 PM
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dkbautosports.com
Join Date: Feb 2009
Location: branford ct
Posts: 3,640
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stay away for galvanized metal !
just good old plain sheet metal is all you need . personally I don't like por products at all ! SEM rust-shield is a better product and a lower cost . if the car has a GALVANISED coating in it like the late model porsches then you can replace it with a E-primer ( Epoxy or Etch ) then a filler primer over the top of the E-primer . |
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06-03-2014, 02:02 PM
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Location: Concord, NC
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Just stay away from galvi all together. Not worth it and it's not the right material. POR-15 is a rust converter and would really use it for just chassis parts that are not intended to be exposed to UV (will discolor). Not really much use for it otherwise, in my opinion.
What are you repairing? Do you have access to a sheet metal brake if needed? Are you welding with a gas equipped MIG wire feed welder? Will it need to be re-coated with something other than paint? First thing I would stress is doing the repair correctly. If there is a patch panel already available, buy it, unless you know how to make it. Doing it wrong will be of no use to you, the next owner, or the value of the car. Do it right. Do it once. Materials... If these are minor repairs to the body (not structural) I would just get a sheet of 18 gauge mild steel (cold rolled type, not hot rolled) from your local steel house or if you just need a little, you can usually get small quantities from your local hardware store. 20 gauge and thinner will just get difficult to weld with a MIG welder and you won't like the results. If it's a structural component, I would probably take a long hard look at the situation. May not be advisable to just start cutting. Welding with a MIG on sheetmetal takes some practice and patience. I would pick up a book or hit YouTube for some tutorials. If you've never welded sheet metal with MIG, only structural tubing, you will find yourself in a warped mess pretty quick if you don't take your time and weld in the right sequence. ALSO! You must have the correct gap and fitment of the panel or again, it will be junk in a hurry. Weld with gas. Do not use flux core wire. And use .024/.025 wire. Make sure the patch is sealed from rust using an epoxy or self-etching primer. Paint stores can put this in a rattle can for you if you're just doing a small area, but if it's a large area, get or borrow a paint gun and buy however much you need. Top coat with a good quality paint system (not single part rattle can paint from WalMart). Use a good quality undercoat system if you're doing work in areas that need it (bottom of the pan, etc.) Hope that helps! Post a thread with your progress. |
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06-04-2014, 09:10 AM
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Thanks for the replies: cold-rolled steel it is.
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I have just picked up a Hobart 140 MIG welder and am going to use it with C25 shielding gas and the smallest gauge MIG wire it accepts (I think that's .023). I have had one introductory welding course and am planning to buy some scrap sheet metal to practice on. I am planning to have an experienced welder come take a look at things too. Quote:
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When you say "good quality paint system" - do you mean a catalyzed/2-part paint? I was planning to coat bare metal that is not UV-exposed with POR-15 and use epoxy primer on anything external (e.g. antenna hole). Sounds like you guys are not fans of POR-15, though. Another question: what do you recommend for cutting patches? Good ol' tin-snips or how about the powered shears, like these from HF: http://www.harborfreight.com/18-gauge-sheet-metal-shear-92148.html Last edited by Ferrino; 06-04-2014 at 09:35 AM.. |
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06-04-2014, 09:26 AM
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Oh yeah! Sounds like you're in good shape with what you mention above. You'll be good with 18 gauge on all that stuff. Keep your favorite body hammer and dolly close by as you weld to counter some of the shrinkage you will see.
Cutting... Use a thin cut-off wheel (.046-.063) on a right angle grinder, GOOD hand shears (don't buy cheap ones, they really do suck), or an electric shear. I've actually had good luck with the HF/Chicago 14 GA electric shear. Works really well. I was really surprised. I bought it in a pinch when I was helping someone with a top-chop job and it worked great. I've not tried the style you provided the link for. In that link they show the other ones I mentioned though. I use mine a lot, now that I have them. ALSO! A WONDERFUL tool to pick up is a shrinking disc. It will help if you have any big distortion problems or tin-canning. Almost like magic! I use the pro-shaper system. You can get them off Ebay. For paint, I would definitely use a 2-part catalyzed system. You should have a local paint place that can color-match or do any custom color you want. There are several types available. Acrylic Urethane single stage 2-part or a base-clear system would probably be good for the application, but there are several systems to choose from. That is a whooooole nother topic though. For a lot of my projects I use TCP Global's house brand (Restoration Shop or Kustom Shop). I've had good luck with it. TCP Global - Quality & Service Since 1974 But they also sell PPG, House of Kolor, etc. Lots of good brands. But I would definitely work with your local paint shop for some guidance on this part. If you decide to you need a paint gun, there are several entry-level guns that will work just fine. TCP, Eastwood, even Harbor Freight's "Professional" series guns will work fine for small jobs, but I won't say they are the best for big jobs. Prep and finish work will be what saves you either way, though. |
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06-04-2014, 10:08 AM
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Thanks. I picked up the HF 14 GA shears last night, along with their welding cart. I forgot to mention that I will also be doing Carrera flares after all the patching, so I am thinking of buying their electric body saw - anyone used this?
Electric Body Saw I don't have and don't plan to get an air compressor large enough to run air tools, so I am thinking this would be good for cutting off the old flares and also excising rust patches. I also have 4.5" and 3" cutting wheels that you mention, which I can run in my angle grinder and drill. TCP are local to me, but I have not been thinking beyond simple rattle-can painting for things like the engine bay and under the hood. I have been reading about the electric turbine-based HVLP sprayers recently - do you think these are OK for spraying catalyzed paints (e.g. epoxy primer) for those who do not want to buy/store a large enough air compressor? Or would I be better off just using those Preval sprayers? Quote:
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06-05-2014, 08:38 AM
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The body saw is handy, but your cuts will tend to be all over the place. They're really intended for some of those hard to reach spots. Sort of a unique tool. If it were me, I would mark out your cut lines and use a cut-off wheel on a right angle grinder. I wouldn't buy anything smaller than a 4.5" cutting wheel and as thin as you can get them. They will make quick work of those fenders/quarters and your cuts will tend to follow the line better. Do a pass with the cutting wheel first to start your cut path, then make the cut on the second pass. The first pass will set the path for the cutting wheel, prevent mistakes, and if you have to make two passes before cutting all the way through, do it. Take your time. If you try and cut through with one pass, it will introduce a lot of unneeded heat into the panel as well as increasing the risk of a mistake. Home Depot and Lowes sell thin cut-off wheels in 4.5 and 5 inch sizes. They usually have .046 and .063. I personally like the offset style, they tend to last longer. DeWalt brand burn up quick and I've had good luck with Diablo brand, and others from Home depot. Expect to go through a half dozen for cutting the fenders/quarters. Don't buy the HF cutting wheels, they're a waste of money and don't cut as well.
Don't use a drill with a cut-off wheel. They are low RPM and it's hard on the drill itself. And it will take you forever. I would definitely consider buying the shrinking disk kit if you're going to do the flares and weld them with a MIG welder. Cutting wheel wells for flares is a big task. For the sake of the car and the value of the car, spend the time and make sure everything lines up right so you don't have to use a lot of filler. Sounds like you have big plans. Do you have a build thread somewhere? Quote:
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06-05-2014, 09:59 AM
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OH! And the sprayer stuff... I guess you could get one of those turbine systems. They're great for humid weather. For the price of one, you could probably buy a gone and decent compressor though.
Are you planning on painting the whole car? If you do, you'll more than likely have to strip off the rattle can stuff first. You will likely have issues with those areas in the future. Doing paint and body work the right way, is not cheap. Doing it the wrong way with the wrong materials is even MORE expensive in the end. In the grand scheme of things, if you can afford the car, you can afford to do it right. |
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06-05-2014, 10:06 AM
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Thanks for the cutting tips - I will pick up one of the thin ones for my angle grinder.
No, I don't have a build thread - going way too slowly! Re. paint: my plan is to repaint the engine bay, under the hood and the wheel wells. I haven't figured out my gameplan for the body yet. Obviously I will need some level of paintwork if I'm welding on rear flares. The current paintjob is likely a cheap respray as it is flaking in a couple of locations, so I would love to take the whole thing back to metal and repaint. I just don't have the budget to farm that work out - my philosophy is to put my budget into restoring the car mechanically and structurally - cosmetic stuff can wait. For a budget respray, I have contemplated stripping the car back to bare metal, epoxy priming and doing bodywork myself, then having the car shot somewhere. For sure, I won't be one of the guys shelling out 7-12K for paint when I could put that to much better use on engine/suspension parts. Yesterday I saw a car that was shot by a DIYer at home (base + clear) and to me it looked amazing - he said he spent $1,000 in materials and no doubt countless hours of prep! |
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06-08-2014, 12:54 PM
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When you pay someone to paint your car, for the most part, it's labor costs that are killing you because of the prep work. The prep work is the hard part. If you are willing to do the body work yourself and put it in primer, applying a base-clear paint system will be a SNAP! Just get good materials, educate yourself on the process and correct tools to get to do the job, and build yourself a rotisserie. Then just dial up your patience and get after it. You WILL need to buy a compressor and a good filtering/water removal system to do it. But all of that is cheaper than buying a paint job. I'm currently finishing a paint job on a car that I've been building for several years (off topic to this forum) and I have about $1000 in paint, filler, and supplies for this job and I would say it's comparable in size to an early 911. Plus abrasives and tools (which I had). A person can EASILY do a paint job for under $2500 doing it themselves with some patience. I say go for it! Don't spend the money on painting it twice. Just touch up the areas you're fixing with a primer and sealer coat. Then when you're ready, strip the whole car and go to it. Running around in primer won't do you a lot of good. Generally speaking, primer is like a sponge for moisture and dirt. It won't stop rust. You have to use a sealer. In most cases you will need to strip it and start fresh for a good paint job that won't give you troubles later in life. Painting over "dirty" primer is a baaaad idea. Some articles you can read were done by a good friend of mine who has been painting his entire life and doing very high end paint jobs. Have a look at his links on this site. They are a good read and broken down nicely. Stripping Paint by Carl Brunson | Hotrod Hotline Paint and Body Tips from Carl Brunson | Hotrod Hotline Preparing a Surface for Paint by Carl Brunson | Hotrod Hotline Spot Painting ... Melting in the Paint Edges by Carl Brunson | Hotrod Hotline Color Sanding and Buffing by Carl Brunson | Hotrod Hotline Cleaning with a Tack Rag by Carl Brunson | Hotrod Hotline Enjoy! Get on it! |
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06-10-2014, 01:17 PM
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Thanks for the articles!
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06-10-2014, 04:33 PM
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Custom Shop - Epoxy Primer PPG, Dupont, HOK, and many other companies, make a similar product. Any catalyzed primer/sealer will do the trick. Just follow the instructions on all paint products and especially the flash times. I once had an English guy tell me (in a thick English accent), "Don't get in a hurry to lay down that next bloody coat. Set an alarm clock, have a beer ready, and ****-off until that alarm rings. Then paint." Flash times are very important. Especially when doing a high-build job where you're laying down lots of material that you plan to block or color sand. Talking about all this has actually got me motivated to finish what I've been dreading working on. I have two other cars, including my 911, that need to be put in sealer because of work that will be done and I plan to use the same primer-sealer system I used before. It's definitely a lot of work, but I'll tell you what, it's very rewarding to make a metal repair and then do the finish work to make it beautiful again. Last edited by scootermcrad; 06-11-2014 at 03:56 AM.. |
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06-11-2014, 03:49 AM
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Thankyou for that product link. So let's say that I want to weld on my new flares and do bodywork on the quarter panel, but want to protect the metal until I can invest the time in a proper paintjob. After smoothing down the welds, would I then shoot the epoxy primer, then apply filler, and then apply the sealer (reduced primer)? Or would I go: filler -> epoxy primer -> sealer.
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06-11-2014, 09:58 AM
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...Well... it seems that you may get a lot of answers, however, most every paint company and filler company will recommend that you start on clean, bare metal, that is free from rust and contaminants, put down filler, then primer, then seal it. I've heard any number of combinations, but that seems to be the most recommended by the manufacturers and that's the way I prefer to do it. You will hear/see arguments about it and I'm not sure if putting down sealer or primer first is in better; never tried it. I've always stuck with filler over perfectly clean metal, followed by primer and sealer. Filler likes a mechanical bond, and depending on the type you buy, some like to chemically bond with the metal. Some fillers have an etching property to them, which is nice when you have a piece of metal that may have started a little pitted from rust. The filler I've grown to love is Rage Xtreme lightweight filler. It is incredible stuff and it will make your life SOOOO much easier when you start cutting it down and pinholes are rare. Al that means less paper, less work, and less stress. I also like to use a skim coat type filler for areas that might have a little pitting or scratches, but don't need any real build. I forget which one I use, but I think it is also an Evercoat product. You will also want to get yourself a long flexible block, or two and buy rolls of paper. The flex-firm blocks are awesome and I like the 16" since they will also work with standard board paper, if you buy it in that size. Having the right tools for the sanding is very helpful, since it's the most agonizing part of the job. Those links I gave you will help you with the prep and paint work. Carl breaks it down way better than I could. Last edited by scootermcrad; 06-11-2014 at 10:53 AM.. |
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06-11-2014, 10:48 AM
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