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Thread: Metal prep of chassis after repairs and shot blasting

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    Jedi Warrior red57's Avatar
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    Metal prep of chassis after repairs and shot blasting

    Hi, I will try to keep this as short as I can. I am finally ready to blast, prime, seal, and paint the chassis. It has taken me about 5 years of part time, whenever I can get to it, work. But all cancer and bent metal has been dealt with - new sills, parts of the outriggers, new shut pillars, new floors, etc. The outer body has new patch panels in doors, boot lid, wings, new nose pieces in the front shroud, and all has been rough fitted to the car and removed again.
    IMG_1963.jpg

    Now I have started blasting to get ready to prime & paint the chassis (most of the chassis was blasted about 10 years ago but has some light surface rust). I have done lots of reading over the years but am still unsure about the next steps.

    My original plan was to blast, blow all dust off and spray an etching primer followed by a good 2 part urethane primer. Then seal and paint - simple enough, right? My subsequent reading says I still need to 'wash' the metal to make sure dust and oils are fully removed - I had mistakenly thought blasting would leave the metal clean enough for painting. Also, some don't recommend urethane primers over etching primers....

    I can't 'blast in the morning and prime in the afternoon' simply because I don't think I will all that quick blasting and the rust bloom can be nearly instantaneous. So I was thinking of using Dupont 5717s and 5718S metal prep system for the bare metal after blasting. This is a phosphoric acid etch cleaning system that requires washing the first application (5717S) off with water. Couple of difficulties - this would require rolling the rotisserie outside (I have a gravel parking lot that won't be friendly to the 4" casters on the rotisserie) since my shop does not have a sloped floor or drains. Then there is the questions of water on all that freshly blasted metal - how well can I dry it and what kind of new rust bloom problems do I have? On top of that, how many hours will it take to scrub and brush all that metal in all those nooks and crannies? If I do this it might take days to get ready to prime after blasting.
    IMG_1964.jpg

    I also considered Eastwood's bare metal etch but it requires wiping down all the metal until your rag stays clean, according to a youtube I watched - again, a lot of time consuming and difficult work.

    I have read so many conflicting opinions/methods that I am really not sure how best to proceed - bodywork and paint is not something I have any real training or background in, but I am in the "do it yourself, you will be glad you did" school.

    I'm hoping some of you have done this as a DIY project and have any suggestions? I'm not looking for shops because I can't afford to pay someone else to work on my toys.

    I must admit, I am close to full circle and back to considering just blowing all the dust off after blasting and prime it.... After all, it only needs to last me another 15-20 years or so.

    Looking forward to a learning about how some of you have solved this problem.

    Thanks in advance,
    Dave

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    Jedi Warrior
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    Re: Metal prep of chassis after repairs and shot blasting

    I used metal wash and then two part epoxy primer. The two part urethane paint. Both arms were ready to fall off after painting all those nooks and crannies.
    Dale

    BJ7 frame up restoration of "the car that would not be restored"; began Dec. 2005, est. complete 2023

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    Re: Metal prep of chassis after repairs and shot blasting

    Eastwood
    Metal Wash cleans and protects in one quick step without using harsh or flammable solvents, and promotes topcoat adhesion on bare metal. Mix with hot water; 7 ozs. of concentrate makes 8-10 quarts of solution (or mix 5 level teaspoons with 1 quart of warm water). Apply by dipping or using a pump spray bottle. Metal wash not only removes residual grease and oil but also leaves a protective film behind that prevents rust for up to 3 weeks in dry storage. Metal wash is an excellent prep for any coating. For faster cleaning (without corrosion resistance) use PRE Painting Prep (10041Z).

    No rinsing or wiping down. Blow dry with compressed air.
    Dale

    BJ7 frame up restoration of "the car that would not be restored"; began Dec. 2005, est. complete 2023

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    Jedi Warrior red57's Avatar
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    Re: Metal prep of chassis after repairs and shot blasting

    Thanks Dale, The Eastwood 'Metal Wash' is different than the Eastwood 'After Blast Metal Prep' that I had looked at earlier (
    and looks like it would be a lot easier to use, not requiring washing off)
    .
    I was interested in the After Blast but the washing down with water was not appealing to me.

    I am continuing to read all I can but it is a very confusing thing - responses on forums and utube are all over the place and it's hard to find any consistency in methods.
    Thanks again,
    Dave

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    Re: Metal prep of chassis after repairs and shot blasting

    Quote Originally Posted by RestoreThemAll View Post
    I used metal wash and then two part epoxy primer. The two part urethane paint. Both arms were ready to fall off after painting all those nooks and crannies.
    Ditto, but with one exception...

    Knowing__AND ADMITTING__that it was impossible to do the whole thing at once, I didn't even try. I essentially divided the chassis into six (6) parts: front, middle and rear, top and bottom.

    I'd blast a section, clean with DP 330 (wax & grease remover, or "Prepsol") and then use DP 40/401 epoxy chromate primer. Depending on how much time left in the day, I'd pick off another, slightly overlapping (blasting off some fresh primer, and painting over some previously primed areas) as I'd go.

    I think the area I dreaded the most was the inside cowl and footwells__the rest, even the engine compartment__was comparatively easy.

    To avoid "dry overspray" start with the top panels (say the scuttle) then progress to the lower panels, like the floors/footwells, etc. Particularly important with the topcoats. You can however lightly mist some thinner (lightly tinted with color, like when you're rinsing out the gun) to blend in some areas, but don't get it "wet."

    I used an acrylic enamel with a polyurethane hardener for the topcoats, and for more solvent resistance, put a clearcoat on top of that. Unfortunately, I was getting pressed for time to complete, and the clear was applied on a VERY HUMID Louisiana evening__moisture was literally suspended in the night air__so I lost a lot of gloss in the chassis. But >30 yrs later, it has held up and doesn't look any different; actually looks appropriate for the underhood finish.

    Have fun, and enjoy it, because once the chassis is painted you've turned the corner, now it's time to put stuff together for keeps!

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    Re: Metal prep of chassis after repairs and shot blasting

    Been doing body work and paint for 45 years. Use a product called OSPHO. Apply really light and let it cure (2-3 days).
    It will now be protected from rust till you wan't to paint. Rub off the "dust" before using a 2 part primer, then paint.
    Jobs I did like this 30 years ago still look good.

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