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Thread: Back coating metal

  1. #1

    Default Back coating metal

    So a few thoughts here that I'm hoping you guys can throw some advice my way again...As I am doing some rust repair on my old Ford, (1979) what do you guys back coat your metal with? Weld thru primer may be one? If I coat it with a rustoleum type product and have to patch in the future, will it cause weld thru issues? Some patches that are cut out are not easily accessed from the backside. Always wonder if you guys try and clean up the backsides at all? I try and read all the posts here and watch youtube vid's but I can't say most guys comment on backside prep much. When I'm taking out a section of metal, I hope to clean the backside of existing, if I can access, so I have something clean for welds to bite into. Am I thinking along the right track? And, once the new piece is in, I'm hoping again to reach behind so I can seal the welds from rusting? Is this a big deal? So many videos show guys happily replacing sections and not treating the backsides. Is this maybe not a big deal? I'm thinking it is, but what do I know lol. My 40 year old truck kind of lasted this long, probably those welds will out live me and not rust through?

  2. #2

    Default

    Maybe rust repair forum woulda been better...

  3. #3
    Join Date
    Nov 2005
    Posts
    45,847

    Default

    Quote Originally Posted by Jimmystoys View Post
    So a few thoughts here that I'm hoping you guys can throw some advice my way again...As I am doing some rust repair on my old Ford, (1979) what do you guys back coat your metal with? Weld thru primer may be one? If I coat it with a rustoleum type product and have to patch in the future, will it cause weld thru issues? Some patches that are cut out are not easily accessed from the backside. Always wonder if you guys try and clean up the backsides at all? I try and read all the posts here and watch youtube vid's but I can't say most guys comment on backside prep much. When I'm taking out a section of metal, I hope to clean the backside of existing, if I can access, so I have something clean for welds to bite into. Am I thinking along the right track? And, once the new piece is in, I'm hoping again to reach behind so I can seal the welds from rusting? Is this a big deal? So many videos show guys happily replacing sections and not treating the backsides. Is this maybe not a big deal? I'm thinking it is, but what do I know lol. My 40 year old truck kind of lasted this long, probably those welds will out live me and not rust through?
    What causes most rust through spots is moisture being trapped behind the metal and if that happens it's usually in a place that's difficult or impossible to access after repairs are made or even after rusted metal is removed. There are some tools and materials that can coat hard to reach areas but it takes some concentration to get it coated properly.

    As far as the welded seams are concerned it's almost impossible to seal them well from the back but like other areas there are some ways of coating them that work. I've found that metal bonding instead of welding can help prevent the seam from leaking when the bonding is done properly.

    Below is a Cavity Wax than can be applied by drilling a hole and inserting an application wand and spraying wax on the back of the repair area.


  4. #4

    Default

    Thanks for that Len. So this cavity wax just sticks to everything? How long could it last? (noticed how I didn't say 'will') Should it be done every few years? I've just welded some small patches on my floor. Easy to reach from underneath. I'm guessing epoxy would be the best sealer for moisture followed with a paint of my choice? I'm thinking a couple, few coats of what we have up here is Tremclad, your Rustolem?

  5. #5
    Join Date
    Nov 2005
    Posts
    45,847

    Default

    Quote Originally Posted by Jimmystoys View Post
    Thanks for that Len. So this cavity wax just sticks to everything? How long could it last? (noticed how I didn't say 'will') Should it be done every few years? I've just welded some small patches on my floor. Easy to reach from underneath. I'm guessing epoxy would be the best sealer for moisture followed with a paint of my choice? I'm thinking a couple, few coats of what we have up here is Tremclad, your Rustolem?
    The only place I use the cavity wax is in closed areas where I can't apply my Fusor sealer. I drill a hole and spray a couple coats of wax using the applicator wand. Since the area is normally closed I think the proper applied wax will last a long time.

    However if you can get to the seams it would pay to use Fusor sealer by pumping it on then spreading it with a brush.




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