Primer for protecting body panels whilst restoring/welding

Discussion in 'How To' started by Joe Hill, Nov 23, 2022.

  1. After lots of digging around on here, I'm still a little bit unclear on a good process for priming/protecting newly welded body & underbody panels/parts to stop rust.

    My current thinking seems to be:
    1. Grind out any rust from surrounding area/parts that aren't being cut out and treat with a rust converter (Bilt Hamber Hydrate 80 seems to have generally positive reviews on here)
    2. Prime any new panels I've fitted, and surrounding treated bare metal with a non-porous etch primer. (Seems like either Bonda Zinc Red primer or Rustoleum come up trumps here for good protection, adhesion and won't catch fire if welding nearby)
    3. Potentially spray on top coat for extra protection If van will be outside during restoration process. (don't know if this is overkill tho if using bonda or Rustoleum)

    Would anyone who's been there and done that be able to advise if this approach seems sound?

    I'm also unclear on which kind of rustoleum product would be best. I understand the combi-colour products work well for people here as underbody paint, but don't know if they make any other kinds that would also work well?

    Any help is really appreciated! :)
  2. Joe, I worked in a garage which had a fair bit of condensation so my approach was to get something on the new metal to protect it as soon as possible. For this reason I went with Bonda prima as it was easy to paint on and unlike other primers is not porous. Other people have used epoxy primers to good effect but I would suggest they are working in a more controlled environment to achieve the adhesion of the base coat.

    Personally I think if you have anything which is more than surface rust, it needs to be cut out and replaced...... I don't think there is any magic bullet for dealing with corrosion.
    Marzydj, ginger ninja and Joe Hill like this.
  3. stirlingmoz

    stirlingmoz Supporter

    I used Rustoleum products on the entire underside of the crewcab after a rusty section of floor was replaced.

    I used their grey primer followed by 2 coats of satin black Combi colour.

    All brushed on (I don’t have a compressor or spray equipment)

    Bit of s mucky job but 18 months later, it’s still clean as a whistle under there and it’s seems tough / resistant to damage. Inside the wheel arches are still good.

    It’s not cheap but I like Rustoleum.

    Joe Hill likes this.
  4. Appreciate the response! Glad to hear you got results you're happy with so far. I'll also be brushing whatever I choose to put on, as I also have no compressor, so that's good to know you can get good adhesion :)
  5. stirlingmoz

    stirlingmoz Supporter

    3E5DEFF3-B490-470C-84A2-2E4026301710.jpeg It was August 2020.

    Just found some pics of my underside painting assistant.
    Joe Hill likes this.
  6. Haha, an all too familiar position for us all!
  7. docjohn

    docjohn Supporter

    Personally, I've never had much success with rust converters; I think I posted something to that effect on another thread. Anyway, I prefer to either cut out any corrosion and weld in zintec steel and then prime with zinc-rich 2K, or, use a proper rust remover to get rid of all corrosion and do the zinc primer.
    Joe Hill likes this.
  8. That's helpful to know @docjohn , thanks so much. Would you reccomend any specific rust remover products you've used which gave you good results? I'm up for doing some experimenting to see what works best
    docjohn likes this.
  9. docjohn

    docjohn Supporter

    Bilt Hamber Deox C is good, if pricey although I think the liquid is better than the gel. Anything that's essentially phosphoric acid works fine: jenolite or similar. I've ended up making my own with a blend of citric and phosphoric acid and made into a gel with xantham gum powder. Sometimes I wipe over with sulphuric acid that I've pickled copper in which gives a nice thin film of copper on the steel which prevents flash rusting for a short while. With all of these it's worth washing afterwards with a mild alkali such as a solution of baking soda. Just try a few things and see what you like; the key is to get rid of the rust and get back to the steel.
    paradox, Joe Hill and Chrisd like this.
  10. Thanks so much for the reccomendations @docjohn ! Always helpful to know what products and methods people have tried tested themselves. I like the sound of the homebrew recipies too. Love a good science experiment!
    docjohn likes this.

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