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Discussion Starter · #1 ·
I am asking this here because you guys know a lot about materials.

So, I have enough old parts laying around in my bins to build another bike. All I need is a frame. I don't have a steel MTB, so I am going to look for a used steel HT frame. I like the look of naked steel with discolored welds. So, my ? is: If I strip a steel frame of it's paint, am I going to find discolored welds?

Also, I have an old RS SID 100 fork that needs new seals. The paint is looking pretty shabby, so while it's apart, I am going to strip the paint off. So, my ?'s are: Does Mg polish up well. Does it do well naked? Or does it corrode? Or, should I give it more of a brushed finish?

Any other ideas would be greatly appreciated.
 

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you won't find discoloured welds and if you're asking these questions you're not a good enough painter to clearcoat it.

Magnesium will oxidise if left uncoated, doesn't polish well and is a total ***** to paint. paint over the existing primers and paint.
 

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Discussion Starter · #3 ·
C Dunlop said:
you won't find discoloured welds and if you're asking these questions you're not a good enough painter to clearcoat it.

Magnesium will oxidise if left uncoated, doesn't polish well and is a total ***** to paint. paint over the existing primers and paint.
It looks like we have a 16 year old who woke up on the smart ass side of the bed this morning.

Unlike your apparently closed mind, I can learn and do anything I put my mind to.

Here's an example. I have never made anything out of wood and I have never ridden a skateboard. I grew up on a huge ranch here in So. Cal. Great place to ride my dirt bikes every day, but not a good place for skateboards. I have always wanted a beautiful long board skateboard, so I decided to make this long board. It's 72", made from two pieces of Red Balau, also known as Red Mangaris. I had to learn every aspect of the build. From designing the shape all the way to applying multiple coasts of varnish, polishing the varnish and applying the strips. Then I had to learn how to ride it. That was just as hard as building it. Here's a couple of pics to keep you entertained, as you can see, it came out perfect:




Here's another example. I polished this frame so good I can use it as a mirror:



So, the moral of the story is, keep your mind open and even you can accomplish whatever you set your mind to. I'm pretty sure I can learn how to clear coat a steel frame, it's not rocket science. And, we don't don't need your Jack Wagon negativity here!
 

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C Dunlop said:
you won't find discoloured welds and if you're asking these questions you're not a good enough painter to clearcoat it.

Magnesium will oxidise if left uncoated, doesn't polish well and is a total ***** to paint. paint over the existing primers and paint.
What does painting ability have to do with knowledge of steel welding?

Why would you say that magnesium doesn't polish well, when it does? People in the automotive industry polish mag parts all the time. If you think that it doesn't polish well, then you're not smart enough to answer Shawn's questions. :rolleyes:
 

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"Fake" discoloration

So Shawn, here's the story:
-When you weld the joints on a steel bike frame, it makes neat pretty colors. Cool. That's the very surface of the metal reacting with the atmosphere (well, ok, basically the oxygen). It's only a surface thing - if you sand off the top few molecules of steel, you won't see it anymore.
-When you want to paint or powdercoat the frame, you need it *very* clean. So generally you sandblast it, or something along those lines, and all the discoloration goes away as part of that process.

If you want to clearcoat over a frame with this look, the best way (IMO, but I'm not an expert on cool looks) is to go back over all the joints with an O/A torch (after blasting) and just heat them up a *little* bit until you get the look you want (if you don't like it on the first try, you can remove the discoloration and try again). Then clearcoat the frame.

Some people call this "fake", but IMO there's nothing wrong with the process unless you way overheat a joint and damage something or pull the frame out of alignment.

-Walt
 

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Discussion Starter · #9 ·
shiggy said:
But it does corrode easily.
Now your the kinda guy I like to hear from! What do you think. Heat up the welds till I get some good color in them and clear coat the frame? And the fork? Polish it till my palms bleed, but stop before I catch it on fire and then clear coat it?
 

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Mountain Cycle Shawn said:
Or maybe, give the steel frame a little polish, then heat the welds for some color then clear?
mag does corrode quickly. Maybe polish and then clear coat?
 

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you can't just clear coat it. the magnesium will oxidise, which forms magnesium oxide, which causes paint to blister. You need to use a magnesium primer, which is not clear. Even if you do manage this, the magnesium will have oxidised slightly when you have had it exposed to the air while preparing it for paint/polish/whatever. I imagine that in an industrial environment magnesium is either painted in a low oxygen booth or a redox agent is used in the primer, or a form of plating is used before paint is applied, or something else that has had a lot of industrial R&D put into it.

I've tried to do both of these things on a moto, they work for about a week. Clearcoating steel is very difficult (you can't see where you are painting and clear primers are (a) rare and (b) don't work. I'm not 16 and not negative by disposition, i'm just saying that you're trying to do two very difficult things.

Magnesium fires are put out with a bucket of sand. If you try to turn it on a lathe it will burn anyway, but you only have to worry about the big-ish flames, not the little ones.
 

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MCS, the board looks nice as well as the polished frame. Doing so takes quite a bit of time if done by hand. I know did this on a Titus once over the winter. Regardless I believe that both are possible it is just a time commitment and getting to know the process with each.

For polishing the Mag fork I would think the finer the finish the longer it would last as there is effectively less surface area or cracks and pours exposed to the atmosphere. I do not know the exact micro level composition of the material to be 100% certain but it sounds logical. Once finished with sanding and polishing the Mag I would think that using a wax would help slow the oxidation. Ever so often you will need to polish and re wax if you want to keep it gleaming or could let it develop an oxide layer and call it done. Either way should like you have a few projects.
 

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as far as the steel goes, this comes up quite a lot. The people that have tried a DIY version of it have reported disappointing results because it's really difficult to keep steel from rusting.

If you look at last year's Speedvagen "surprise me" paint job, it features fake welding discoloration under clear. I am not sure what the clear coating was, but the only clear over bare metal that makes sense to me is powder.
 

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Mountain Cycle Shawn said:
Now your the kinda guy I like to hear from! What do you think. Heat up the welds till I get some good color in them and clear coat the frame? And the fork? Polish it till my palms bleed, but stop before I catch it on fire and then clear coat it?
I would not bother stripping a steel frame to clear coat. Raw is something you get when you you do not want to do anything, and are willing to accept a little rust.

I want to try this stuff on a never-painted steel frame: http://roadsters.com/gibbs
(somebody on the board mentioned it several years ago)

No desire to strip a frame to try it. And it would not look the same in any case.

I would keep a nice thick coat of opaque paint on the fork.
 

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unterhausen said:
as far as the steel goes, this comes up quite a lot. The people that have tried a DIY version of it have reported disappointing results because it's really difficult to keep steel from rusting.

If you look at last year's Speedvagen "surprise me" paint job, it features fake welding discoloration under clear. I am not sure what the clear coating was, but the only clear over bare metal that makes sense to me is powder.
I have a few small parts I fillet brazed, then used a wire wheel on them and powder coated with a transparent red. No signs of rust 3-4 years later.

I do often wonder how much rust is under an opaque paint/powder that we never see.
 

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Discussion Starter · #17 ·
shiggy said:
I would not bother stripping a steel frame to clear coat. Raw is something you get when you you do not want to do anything, and are willing to accept a little rust.

I want to try this stuff on a never-painted steel frame: http://roadsters.com/gibbs
(somebody on the board mentioned it several years ago)

No desire to strip a frame to try it. And it would not look the same in any case.

I would keep a nice thick coat of opaque paint on the fork.
I didn't know powder coat came in clear.

the Gibbs looks very interesting. I'm thinking a couple applications of that could keep a steel frame from rusting. I live in So. Cal., about 45 minutes north of Los Angeles, just west of the San Fernando valley, or just The Valley. And I don't ride in the rain or in the mud, and for the most part, it's pretty dry here most of the time. Although it did snow here today, No, I'm serious it did. I can't even remember the last time that happened. I know it snowed here in '88 and one other time since then.

Anyway, I like to do projects, especially bike projects, so I won't mind stripping the pain off a frame and doing all the other work. Thanks for the suggestion Shiggy!
 

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C Dunlop said:
Magnesium fires are put out with a bucket of sand. If you try to turn it on a lathe it will burn anyway, but you only have to worry about the big-ish flames, not the little ones.
I've turned mag on a lathe with no problems. proper feed/speed and lubricant (just like any other material), and it's safe.
 
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