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Aluminum frame corrosion and repaint

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Aluminum frame corrosion and repaint

Old 02-11-24, 07:39 PM
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Aluminum frame corrosion and repaint

I found a 1987 Trek 1200 Frame and fork (ser No. 305758) at the Bike Exchange on Wednesday and when I looked closely there were a number of blisters in the paint due to corrosion.

I was told to just throw the frame in the trash as we have more frames than we need.

I brought it home and used a sharp knife to scrape the rusted spots till I cleaned off all the corrosion and I don't think there is anything structural. .

My thought is to treat the raw aluminum with Rustoleum aluminum primer and paint the rust spots only with a blue that matches the frame color, then paint the frame with a sponge pattern in white or yellow to match the decals.

Any wisdom on how to treat the corrosion would be appreciated.

I read that there is an etch that you should use before priming . I am open to suggestions from the hive mind on this.

One strange detail on this bike is that while the frame is aluminum the fork is steel. It appears to be the original fork. Not sure why they would have done this.






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Old 02-11-24, 08:11 PM
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A lot of those areas are where steel parts are attached to the bike, so it is probably a galvanic reaction between them. Not necessarily a big deal.

On Trek an Cannondale aluminum of that era, steel forks were the original offering, and then later were the fork for lower end models. You can see this in the catalogs, which are all available online.

Another way to go is to strip the frame with Citrus strip and then polish it with a buffing wheel and stainless polish. But your plan sounds good.
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Old 02-12-24, 01:39 AM
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That's just enough finish damage to justify a full strip and repaint, IMO. Especially as the frame isn't that rare or valuable, so originality is not as much a priority for most people.
it will also help you find any other areas of corrosion that might still be hidden under the paint and can bubble up later.
Some might suggest polishing up the frame to a mirror or satin finish after stripping it and just do a clearcoat paint job over it. Doing so will result in an awesome look8ng frame, but the look will not last a long time as corrosion can still form under the clearcoat as desp8te what most people think, most paint is quite porous. Clear anodizing will better protect the aluminum, but anodizing a whole bike frame will be quite difficult, if you do not have the right materials and equipment to do so.
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Old 02-12-24, 07:13 AM
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Originally Posted by Chombi1
That's just enough finish damage to justify a full strip and repaint, IMO. Especially as the frame isn't that rare or valuable, so originality is not as much a priority for most people.
it will also help you find any other areas of corrosion that might still be hidden under the paint and can bubble up later.
Some might suggest polishing up the frame to a mirror or satin finish after stripping it and just do a clearcoat paint job over it. Doing so will result in an awesome look8ng frame, but the look will not last a long time as corrosion can still form under the clearcoat as desp8te what most people think, most paint is quite porous. Clear anodizing will better protect the aluminum, but anodizing a whole bike frame will be quite difficult, if you do not have the right materials and equipment to do so.
I polished a Cannondale in 1990, and it still looked good 20 years later with no clear coat. I wouldn't both with a clear coat.
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Old 02-12-24, 10:09 AM
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If you're going to repaint any exposed areas need to be treated with Alodine to prevent corrosion. You clean them with alcohol then apply the Alodine. It can be brushed on but may thicken around the edges and if you try to sand it smooth you will expose the base metal again and have to start over. It's easier to get an even application using a Prevail sprayer or air brush.
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Old 02-27-24, 05:50 PM
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Here's an update on the Trek 1200.
After looking at the price quoted for Alodine ( high) I chose to sand the bear metal areas, treat with naval jelley, then prime with Rustoleum aluminum primer , I then mixed up some paint from my many sreay cans and brushed on a blue that almost matched the original .

After masking off all the decals and lightly sanding everything I used sponges to dab / smear white, maui blue and mint green Rustoleum gloss enamel (from spray cans) over the entire frame and fork.

Once this dried I removed the masking tape and carefully daubed paint in and around the lettering to match the rest of the bike, then built it up with parts from the Bike Exchange including a 3 x 6 drive train and nifty shimano shifter which is a combination thumb and trigger mech.

The bike is tall at 62cm. it also sports a very long seat post and stem so could probably accomodate anyone from about 5'10" to 6' 4" or even taller.

I don't suppose the color will appeal to the super macho types but as I always say "it takes a real man to wear pink". Plus , if there are any female basket ball players here in the Bay Area that want a kewel ride on campus at Stanford or Cal, come on down. We have just the bike for you.

all masked off and ready for the sponges


an hour later and . . .Ta Da !!!!

I had a set of white, blue, and red tires in my shop that no one else wanted to use. White was the perfect colot for this build.

Various Shimano bits for the drive train


The cockpit, with cheepo "leather " grips from Amazon that are foam grips with the vinal sewed over. actually quire comfy.

looks like an easter egg on wheels

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Old 02-27-24, 06:31 PM
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Originally Posted by capnjonny
I don't suppose the color will appeal to the super macho types but as I always say "it takes a real man to wear pink".
About the only thing that middle school taught me was that I was never going to make the super macho types happy, and to live my life however I wanted. And that bike looks GREAT! The white tires are just right.
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Old 02-27-24, 07:55 PM
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Originally Posted by Murray Missile
If you're going to repaint any exposed areas need to be treated with Alodine to prevent corrosion. You clean them with alcohol then apply the Alodine. It can be brushed on but may thicken around the edges and if you try to sand it smooth you will expose the base metal again and have to start over. It's easier to get an even application using a Prevail sprayer or air brush.
Funny.

Originally Posted by Kontact
I polished a Cannondale in 1990, and it still looked good 20 years later with no clear coat. I wouldn't both with a clear coat.
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Old 02-27-24, 08:01 PM
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FWIW the steel fork was meant to soften the harsh ride of the all-aluminum frame AFAIK.

You did good with that sponge job.
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Old 02-28-24, 01:59 PM
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Wow, great curb appeal on that build. I canít think of a better outcome.
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Old 02-28-24, 07:23 PM
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Originally Posted by Kontact
Funny.
I'm glad your bike has maintained it's finish all these years, I bet it looks great, but it is the exception, not the rule. As of last month I've been in Quality Assurance for 45 years, mostly at defense contractors that manufactured miltary vehicle bodies, weapons systems or aircraft and aerospace systems such as air to air refueling, oxygen generation and air crew safety systems that have to operate in a wide range of environments, most of them involve exposure to salt water. Some of that time over a 20 year period involved testing paint and chemical coatings in an environmental chamber for corrosion resistance. I'm not an "expert" but I do have a little bit of practical experience with the subject.
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Old 02-28-24, 08:17 PM
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Originally Posted by Murray Missile
I'm glad your bike has maintained it's finish all these years, I bet it looks great, but it is the exception, not the rule. As of last month I've been in Quality Assurance for 45 years, mostly at defense contractors that manufactured miltary vehicle bodies, weapons systems or aircraft and aerospace systems such as air to air refueling, oxygen generation and air crew safety systems that have to operate in a wide range of environments, most of them involve exposure to salt water. Some of that time over a 20 year period involved testing paint and chemical coatings in an environmental chamber for corrosion resistance. I'm not an "expert" but I do have a little bit of practical experience with the subject.
Sure - more challenging environments will dull aluminum much faster. But it is important to consider that a lot of components in the past were just polished, not anodized. Unless you intend to ride winter Wisconsin roads or on a windy coastline, aluminum will look good for a long time - especially if you wax it and then keep it wiped down.

For a space shuttle I'd make different recommendations as well.
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