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Technical Advice on rust pits

Discussion in 'The Hokey Ass Message Board' started by Mark Parylak, Apr 9, 2019.

  1. Mark Parylak
    Joined: Jan 12, 2019
    Posts: 4

    Mark Parylak

    I'll keep this short. I've read probably 200 posts on this subject and cant make up my mind.
    I have fenders I'm working on. 1941 plymouth. Not bad shape, I sanded them down. Clean metal. Except for the areas where some pitting is. I dont want to keep grinding and weaken the metal and I dont want to sand blast and wrap it all up...
    So ive read everything from using metal prep to ospho to different primers to rust converters or rust encapsulators, acids. Etc.
    I have por 15 metal prep. That good enough to take care of that little bit of rust left in them pits before I put on my filler over it?
    Thanks in advance for any input.
     
    Last edited: Apr 9, 2019
  2. Oldioron
    Joined: Dec 12, 2018
    Posts: 511

    Oldioron
    Member

    Hell no, get the rust out.........period.
     
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  3. KenC
    Joined: Sep 14, 2006
    Posts: 222

    KenC
    Member

    Depends on the number of pits. If just a few, or small areas,I'd carefully sand blast. Most older fenders have enough convex shape to prevent warping if one is careful with air pressure and time. If small pits over a large area, my go to magic juice is Picklex 20. More expensive that the alternatives, but a little goes a long way if you follow the directions. It will also prevent rust on dry metal stored indoors for a long time, unlike some of the other rust treatments.
     
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  4. squirrel
    Joined: Sep 23, 2004
    Posts: 41,951

    squirrel
    Member

    if you sandblast with a small nozzle and reasonable pressure (90 psi or less), it should not warp the metal. Folks get into trouble when they use an industrial sandblaster on sheet metal. I've been using small home type blasters for decades, and never had any issue with warping. But it does take a long time to clean up large parts.
     
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  5. Mark Parylak
    Joined: Jan 12, 2019
    Posts: 4

    Mark Parylak

    Wow. Thanks for the quick replies. You guys are all right! :)
    Sounds like gentle sand blasting is what to do...
    Now second question... what filler is better over the clean pitted areas? All metal, a fiberglass reinforced, or a premium type filler?
     
  6. squirrel
    Joined: Sep 23, 2004
    Posts: 41,951

    squirrel
    Member

    did you make holes in the metal when you blasted it?

    I'd want to answer this question, before trying to figure out what to do.
     
  7. Mark Parylak
    Joined: Jan 12, 2019
    Posts: 4

    Mark Parylak

    I'm gonna blast it later after work. I dont think I'll blast through it, fingers crossed. If it does than I'll probably be doing some cutting and patching with the mig welder...
    Let's say it doesn't blast through.. what'd you recommend?
     
  8. testdepth
    Joined: Dec 23, 2018
    Posts: 86

    testdepth

    If the fenders are off I would use Evapo Rust because I know it works and you can use the product over and over until it's gone. Need a way to create a dam to hold the product in place (maybe playdoh). I used this stuff on an antique axe head as I did not want to damage the original metal by grinding on it. Here is the before and after Evapo Rust on my axe. It removed the rust from the pits and I rubbed it with a little steel wool to clean it off.

    AXE head rusted rt.jpg Axe refinished head close.jpg
     
  9. ricky_tbird
    Joined: Aug 20, 2015
    Posts: 11

    ricky_tbird
    Member

    I used to build cold molded wood boats so am versed in the magic of epoxy. To fill a badly pitted fender I mix up some epoxy and thicken it with cab-o-sil (fumed silica, thixotropic agent) and maybe some micro balloons and spread it over the rust pits. Cab-o-sil is a bitch to sand, micro-balloons make it easier but don't add any strength. Sand the epoxy and follow with epoxy primer. Seems to work for me.

    We once faired a steel hull sailboat this way but used epoxy entirely mixed with micro-balloons. Spread it over the hull with a notch trowel and faired it with long boards. Once sanded we went back and filled the gaps in the epoxy with another coat and sanded again. Boy that was a lot of work but the boat came out great.
     
    Last edited: Apr 9, 2019
  10. squirrel
    Joined: Sep 23, 2004
    Posts: 41,951

    squirrel
    Member

    If you get all the rust out of the pits, you might just use an epoxy primer, then use normal filler to fill the pits, then sand and use a K2 (urethane) primer, and do the normal sand/prime thing till it's perfect.
     
  11. fordrodsteven
    Joined: Apr 1, 2017
    Posts: 96

    fordrodsteven
    Member

  12. fordrodsteven
    Joined: Apr 1, 2017
    Posts: 96

    fordrodsteven
    Member

    X2 (100%)
     
  13. Mahty
    Joined: Nov 20, 2016
    Posts: 30

    Mahty

    I’ve been testing every rust remover i can find. Citric acid and a wire brush works best for me. Just used a rag soaked in it, lay I on the area if soaking isn’t an option. Cleans ALL the rust out. IMG_8162.JPG IMG_8171.JPG


    Sent from my iPhone using The H.A.M.B. mobile app
     
  14. This is generally the best way, but you can get rust out of pits if it isn't super-deep with a cup wire brush on a grinder. Some of the same cautions apply; keep the brush moving, don't let a lot of heat build up or you will get warping. I wouldn't try this on thin, relatively flat panels. Older (thicker) curved metal, it can work...
     
  15. Mark Parylak
    Joined: Jan 12, 2019
    Posts: 4

    Mark Parylak

    Mahty.
    Those pictures you posted are identical to the pits I have on my fenders...
     
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  16. rusty valley
    Joined: Oct 25, 2014
    Posts: 672

    rusty valley
    Member

    all good advise above. living in the rust belt i have been fighting rust pits for 50 years. i have a big sandblaster, and a little siphon blaster, and the bead blast cabinet, and have used rust 911, evaporust, molasses, and have experimented with electrolysis untill i wrecked my favorite battery charger. my findings are this NOTHING gets it all!!!! there will always still be tiny black pits you cant get without grinding away gobs of metal,and we are not going to do that. so, i feel everything should still be treated with oshpo or similar products that will stop whats left from growing. its cheap and effortless to do after all the time you spent on the other processes to get to that point. the other thing is, although we try to do the best job possible, in most cases the part will out live most of us even with a poor prep job
     
  17. indyjps
    Joined: Feb 21, 2007
    Posts: 3,572

    indyjps
    Member

    Agree, I still like an acid etch after blasting before I shoot costly paint. Neutralize well, DA, prime.

    Citric acid and oxalic acid are becoming my go to's. Reasonable cost and Im more patient than I used to be, not quite patient enough for molasses.
     
  18. PHIL COOPY
    Joined: Jul 20, 2016
    Posts: 364

    PHIL COOPY
    Member

    If you get a few pinholes a 000 torch tip and some silicon bronze rod will fill them in without warping.
     
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  19. Mahty
    Joined: Nov 20, 2016
    Posts: 30

    Mahty

    It works like a charm. It’s cheap, fast, and it doesn’t burn your eyes or cause more rust. Wash off with soap and water. It even takes that wormy looking rust off. Pics don’t lie.


    Sent from my iPhone using The H.A.M.B. mobile app
     
  20. Pats55
    Joined: Apr 29, 2013
    Posts: 123

    Pats55
    Member
    from NJ

    Get rid of the pits. My primer[ three coats] will level up sheet metal pits. Besides leveling up the pitting it will do 8000 hours salt spray. You can put any kind of primer or paint over it there's no need for fillers to bite you in the ass later. This works well for for irregular surfaces where you can't sand. I have an old seat frame that I will, blast then prime. This'll be my next video project and I'll post it next week
     
  21. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 7,194

    mgtstumpy
    Member

    Here goes, try this method.;)
     

    Attached Files:

  22. Im with Mahty, soak a rag in water/ powdered citric acid mix. let it sit overnight, wire brush off the loose rust and youll be left w clean metal.

    Sent from my SM-J727T1 using The H.A.M.B. mobile app
     
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