1971 Montreal project - Alfa Romeo Bulletin Board & Forums
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post #1 of 116 (permalink) Old 04-02-2018, 05:43 PM Thread Starter
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1971 Montreal project

Cleaning up the body on my 1971 Montreal before it heads off for paint
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1971 Alfa Romeo Montreal, 1972 BMW 2002tii Alpina A4S, 1971 Triumph TR6
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post #2 of 116 (permalink) Old 04-03-2018, 02:29 AM
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That's what I would call a very clean slate to work from. I gather you had the car acid dipped?
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1971 1750 GTV 105.48 (sold), 1972 1300GTJunior (sold)
1969 1750 GTV 105.5 , 1972 Montreal
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post #3 of 116 (permalink) Old 04-03-2018, 03:01 AM
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Hello mtbjeff, This is such a neat sight. If it was acid dipped, I would be interested in what you did exactly as my chassis is being dipped this week (google “carblast.de Facebook Montreal“ if anyone is interested). It would also be reassuring as it proves it can be dipped without damaging the factory tin in the lower corners of the windscreen which I was told is a small risk. Are you going to have it electro coated as well? Cheers, Christian
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post #4 of 116 (permalink) Old 04-03-2018, 03:31 AM Thread Starter
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Hello mtbjeff, This is such a neat sight. If it was acid dipped, I would be interested in what you did exactly as my chassis is being dipped this week (google “carblast.de Facebook Montreal“ if anyone is interested). It would also be reassuring as it proves it can be dipped without damaging the factory tin in the lower corners of the windscreen which I was told is a small risk. Are you going to have it electro coated as well? Cheers, Christian


Hi Christian, Yes it was acid dipped and I’m very happy with the results. I did remove the aluminum spacers in the front frame rails for the steering box and steering idler arm before the dip. I’m reinforcing both those locations and it aided in flushing out the inside of the frame rails.

I had no problems with the Tin welded locations on the car. Getting the body this clean has really helped in finding any flaws in the car, cracked seat mounts, rust repair or broken spot welds after 47 years.

I also dipped the Fuel tank and it is incredibly clean too. I’m really happy with the process.

The car was dipped at Metal Works in Eugene Oregon.

Jeff
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1971 Alfa Romeo Montreal, 1972 BMW 2002tii Alpina A4S, 1971 Triumph TR6
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post #5 of 116 (permalink) Old 05-26-2018, 03:27 PM
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I'll be following this project. Has anything progressed since the initial photos? Peter.

1966 GTA replica, 1967 Duetto, 1987 Quadrifoglio
1972, 1973, 1974 Montreal
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post #6 of 116 (permalink) Old 05-26-2018, 03:44 PM
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Wow ... still scares the heck out of me the concept of acid dipping your car, especially as these old cars were not (I believe) designed for dipping as more modern cars were so there would be drain holes, etc.

Yes, any updates?
Pete

'71 1750 Series 2 GTV:
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post #7 of 116 (permalink) Old 05-26-2018, 05:11 PM
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......especially as these old cars were not (I believe) designed for dipping as more modern cars were so there would be drain holes, etc....
Tha was probably true for the pre 1960's cars....but the Montreal, GT Junior and GTV's were definitely dipped. The large holes in the floor pan that are plugged with the rubber bungs are there for this very reason...drainage. As well there are openings in the lower flange of the sills that will allow liquids to drain out. The site below has photos of this and a nice little slideshow of other interesting Montreal photos.

Montreal Assembly | alfa-male


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1971 1750 GTV 105.48 (sold), 1972 1300GTJunior (sold)
1969 1750 GTV 105.5 , 1972 Montreal
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post #8 of 116 (permalink) Old 05-26-2018, 09:26 PM
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Piece of art! I would be tempted to just steel wool the surface, clear coat it and hang it up on my living room wall!!!
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post #9 of 116 (permalink) Old 05-27-2018, 02:44 AM
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I am not sure these stripping baths are acid based I used to do a lot of paint stripping on furniture and metal years ago and I had a 7' by 5' by 4' tank full of caustic soda or sodium Hydroxide as it says on the label, it handled most paint well enough, old enamels and oil based, varnishes. The tough ones were water based and polyurethane types, I do remember once putting in an aluminium grill for too long it was partly dissolved when it I took it out! If someone knows what the acid is I'd like to know what it is.
Tim
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post #10 of 116 (permalink) Old 05-27-2018, 06:28 AM
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What were the cars being dipped in 20-30 years ago to get the paint off? As a guess is was caustic soda. When the paint comes off, the caustic soda (NaOH) interacts with the steel (Fe) under the paint and you get a thin Magnetite (Fe3O4) layer on your panel, which is black/blue in colour. Magnetite has a Mohs’ hardness level of 5.5 to 6.6 and the only way you can get that black Magnetite later off is to use something that has a higher hardness!

Last edited by Steve105; 05-27-2018 at 06:32 AM.
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post #11 of 116 (permalink) Old 05-27-2018, 07:34 AM
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Steve is the usage of an acidic neutralizer the answer after the dipping process? I used to use acetic acid otherwise know as Vinegar on the gear that was dipped in the stripping tank, it was first thoroughly pressure washed with water then sprayed with vinegar.
Tim
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post #12 of 116 (permalink) Old 05-27-2018, 10:01 AM
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Acid dipping may be fine. My personal concern would be in the areas the acid has reached (any boxed sections, i.e. rocker panels, A Pillar, B Pillar, etc.) that you cannot get the neutralizing solution into with spraying. It would almost having to dip the car in a acidic neutralizer tank after the acid dipping...
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post #13 of 116 (permalink) Old 05-27-2018, 10:42 AM
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The car I purchased was sitting in 'black primer' for the last 20 years . When it came time to get rid of what I thought was black primer I was wrong, it was magnetite.
I did send the car to have it lightly blasted to get the black layer off. It could be the magnetite was too hard for the aluminum oxide or garnet abrasive which just bounced off the magnetite film, then the etch primer over the top the magnetite well some one forgot to tell me the black layer did not come off !, they just put lots of grey etch primer which was also very hard as well. I had the car sitting inside garage for about 2 years. then took it to the panel shop. The magnetite layer was still there under the grey etch primer I just did not know it, so not only the etched primer would not come off neither did the black film (magnetite) double trouble.
I just had to work it out as quickly as possible overnight as my panel/paint guys were upset as it was taking too long to prepare!
The simple job became complicated and more costly. I remembered some one said to me it was dipped before. The only black film/coating possible on mild steel was to have it dipped or in caustic soda (Sodium hydroxide). I don't think caustic = acid, Caustic soda = alkaline. This was the same technique they used back in the old days when they did not have access to high quality harden steels for gun barrels. That is why early gun barrels are blackish /blue. In one chemical article they talk about 'magnetite films produced on the mild steel surface could prevent or minimize the corrosion on its surface' which in effect what happened to my car as it had no paint on it for 20 years. Only problem is magnetite has a slippery structure so some paints primer / filler will not stick to it so compromising the job. Unless you like the black magnetite look.

I don't know all the details, but logic tells me if you leave painted steel (car or parts) in caustic soda NAOH and it works faster than you expect thus giving more time for the steel to be exposed you will get a thicker film layer of Magnetite, making it harder for you to get it off latter. We had to use Zirconium 3M sanding discs which got us mostly there.

Last edited by Steve105; 05-27-2018 at 11:20 AM.
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post #14 of 116 (permalink) Old 05-27-2018, 11:25 AM
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Quote:
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Steve is the usage of an acidic neutralizer the answer after the dipping process? I used to use acetic acid otherwise know as Vinegar on the gear that was dipped in the stripping tank, it was first thoroughly pressure washed with water then sprayed with vinegar.
Tim
Not sure you may be talking about HCL Hydrochloric acid which I don't know much about except I don't like for use in rust removal. I prefer Molasas solution for rust removal as they used back in the old days, but it can get stinky and stains your hands.
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post #15 of 116 (permalink) Old 05-28-2018, 01:09 AM
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monte chassis is way cool...
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