So I just got my hands on an old Concorde Aquila as a renovation project, but I dont know a lot about old bikes. The chrome on this frame is rusty as hell, but hopefully ill be able to save it.
Which year is it from? somewhere between late 80s and early 90s i recon. It has Shimano 600 if that helps.
What kind of tubing? SL, SLX or TSX or something else? not sure of the seatpost dia unfortunately.
I threw in a few pics which will hopefully help.
BB serial: 080644

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Shimano 600 Ultegra was released in 1988 but the dual pivot brake option wasn't available until 1991. The STI brifters were released in 1992, so the presence of down shifters suggest it's 1991, provided everything is OEM. The red bordered fork decal, if OEM, indicates SLX or TSX, as opposed to SL. The bicycle obviously needs an overhaul so removing the bottom bracket will allow you to inspect the inside of the ends of tubes to determine if it actually is SLX or TSX.

The phrase "rode hard and put away wet" comes to mind, except it looks more like it was left outside after being rode hard. That was a nice bike, hopefully the damage is not all the way to the inside.

Probably a really good rider if you can bring it back. Oxalic acid bath would help the fork.

Wow, thanks for all the great answers! Unfortunately it didnt get the love it deserves! The fork should be saveable, just need to get some acid. Abit unsure if the seatstay can be saved. Should i sand it down, or is there a better way to find out?

Also, what should i look for inside the tubing to get my answer?

This is what the helical ridges inside SLX and TSX look like.

I wouldn't sand it down unless you plan to re-chrome it, in which case you will need to polish it to a 'chrome finish' before the re-chroming.
I'm not a frame-builder but I don't think that part of the seat stays takes a lot of stress or is a critical safety risk so if the remaining metal appears solid I would feel safe riding it. Oxylic acid should remove only the rusted metal and not any sound metal so get rid of the rust first and see what's left.

Would it work to put the whole frame and fork in a acid bath, or would that ruin the paint?

oxalic acid will not harm the paint. Decals...depends but usually OK, too. Search the forums for more details and tips on how to do it.

Hey guys, just wanted to give you an update on how its going. I've almost stripped it down except from the cranks, as im awaiting the tools for it. Most of the parts seems to be in pretty good condition and has been cleaned up. The frame and fork is still quite rusty, but ive managed to get rid of the surface rust with steel wool. Unfortunately, the rest of the rust is on bare metal and the chrome is gone. The OA might make that dissapear if i go that route, but then I'll "need" to get it rechromed. Tips and suggestions are welcome as this is my first restoration.
Here's a few pics:

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find a new fork on eBay if possible? are you using a power tool to try and get that rust off? a simple dremel with a wire brush attachment could work too.

That is an option if i find one, but im trying to keep the cost down and id like to have it original even if that means it'll have some wear and tear.
At this point ive only used steel wool by hand as im unsure of using powertools. Wouldnt it scratch the chrome/paint?