To polish or not to polish take 2
07-25-2001, 02:18 PM
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To polish or not to polish take 2
OK, the first time I brought this up I was just trying to see what I could get started, this time I actually have a point.
You should not polish alloyed aluminum if it is subjected to any load or significant vibration because it will crack. The aluminum parts on your car come either anodized or coated to prevent intergranular corrosion from occuring. If you remove this protective layer you expose the alumnium to the environment, which will allow it to begin to corrode within its crystal structure and eventually crack.
I used to manage a bicycle shop in Atlanta. We sold Cannondale bikes which are aluminum tubed bicycles. Some of our customers would buy a Cannondale, take it home and strip the paint. Most often they would polish the frame, but without exception the frames would crack and fail, polished or not.
After a while Cannondale caught on and started selling frames which where polished and clear anodized to prevent the problem.
Anodization helps because it creates an electrical boundry layer, thereby preventing the (galvanic) intergranular corrosion.
How about American Airlines planes with the polished fuselage? The skins of aircraft are a sandwich of alloyed aluminum, for strength, between two layers of pure aluminum, which does not corrode. Even still, stress cracks form around the rivet holes which eventually lead to failure, like at 30,000 feet over the Pacific.
If you must polish, at least keep your mitts off of the aluminum suspension pieces.
You should not polish alloyed aluminum if it is subjected to any load or significant vibration because it will crack. The aluminum parts on your car come either anodized or coated to prevent intergranular corrosion from occuring. If you remove this protective layer you expose the alumnium to the environment, which will allow it to begin to corrode within its crystal structure and eventually crack.
I used to manage a bicycle shop in Atlanta. We sold Cannondale bikes which are aluminum tubed bicycles. Some of our customers would buy a Cannondale, take it home and strip the paint. Most often they would polish the frame, but without exception the frames would crack and fail, polished or not.
After a while Cannondale caught on and started selling frames which where polished and clear anodized to prevent the problem.
Anodization helps because it creates an electrical boundry layer, thereby preventing the (galvanic) intergranular corrosion.
How about American Airlines planes with the polished fuselage? The skins of aircraft are a sandwich of alloyed aluminum, for strength, between two layers of pure aluminum, which does not corrode. Even still, stress cracks form around the rivet holes which eventually lead to failure, like at 30,000 feet over the Pacific.
If you must polish, at least keep your mitts off of the aluminum suspension pieces.
07-25-2001, 03:03 PM
#2
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Manning, what are you trying to start? You may have some good points but I think you are going to mislead some people.
I'm no materials expert but I do know that aluminum is very brittle and quite subject to repeated flex stress doing a crystallization fracture. This will happen eventually no matter what you do. Unless you never stress it.
I don't believe the act of polishing is a problem and probably would be good to relieve stress points. Similar to drilling a round hole at the end of a crack on an airplane's skin to stop it from propagating.
Now polishing and then trying to protect and preserve that mirror finish is an issue that shouldn't be treated lightly in high stress components as AL is highly reactive. Starts to oxidize the micro second you expose it.
But I don't think many Listers are down polishing critical parts, wheels being the notable exception. And that may be where you are headed. To that I agree, watch out.
But for cast manifolds and valve covers, who cares?
From a guy that sails and is always concerned about losing an older AL mast in a blow - now that would be a real problem on par with losing a wheel turning to avoid a rock wall at high speed. With these lighter wheels maybe the rock wall stories will become as frequent as big trouble and death from snapped sticks?
I'm no materials expert but I do know that aluminum is very brittle and quite subject to repeated flex stress doing a crystallization fracture. This will happen eventually no matter what you do. Unless you never stress it.
I don't believe the act of polishing is a problem and probably would be good to relieve stress points. Similar to drilling a round hole at the end of a crack on an airplane's skin to stop it from propagating.
Now polishing and then trying to protect and preserve that mirror finish is an issue that shouldn't be treated lightly in high stress components as AL is highly reactive. Starts to oxidize the micro second you expose it.
But I don't think many Listers are down polishing critical parts, wheels being the notable exception. And that may be where you are headed. To that I agree, watch out.
But for cast manifolds and valve covers, who cares?
From a guy that sails and is always concerned about losing an older AL mast in a blow - now that would be a real problem on par with losing a wheel turning to avoid a rock wall at high speed. With these lighter wheels maybe the rock wall stories will become as frequent as big trouble and death from snapped sticks?
07-25-2001, 03:23 PM
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Well, I guess what I am getting at is why spend a couple of weekends coating yourself in polishing compound when you could be compromising your health (from inhaling the dust and schmootz) and the parts integrity.
I absolutely stand behind not polishing very critical parts such as suspension pieces and wheels perhaps, but why take the time to polish out a intake manifold only to have it crack at a flange (at some perhaps distant point in the future) because of intergranular corrosion. That big plenum bounces even if it is braced.
Every single home polished frame that came into our shop wound up with a cracked of head tube and a very injured rider. Cannondale got sick of seeing this happen and started polishing the frames themselves. The only difference is they clear anodized the framed to prevent galvanic reaction.
On the other hand, I do see the point in polishing to prevent stress risers, such as in a connecting rod, but then that is a different material and has different structural limitations.
But like you said , what difference does it make on a part like a cam tower. Well, other than the fact that most people do a half-*** job preparing and polishing the surface and instead of looking good, all you see are the casting defects and voids.
On the other hand, pulling all of those parts does give you a chance to replace all of the seals and gaskets
I absolutely stand behind not polishing very critical parts such as suspension pieces and wheels perhaps, but why take the time to polish out a intake manifold only to have it crack at a flange (at some perhaps distant point in the future) because of intergranular corrosion. That big plenum bounces even if it is braced.
Every single home polished frame that came into our shop wound up with a cracked of head tube and a very injured rider. Cannondale got sick of seeing this happen and started polishing the frames themselves. The only difference is they clear anodized the framed to prevent galvanic reaction.
On the other hand, I do see the point in polishing to prevent stress risers, such as in a connecting rod, but then that is a different material and has different structural limitations.
But like you said , what difference does it make on a part like a cam tower. Well, other than the fact that most people do a half-*** job preparing and polishing the surface and instead of looking good, all you see are the casting defects and voids.
On the other hand, pulling all of those parts does give you a chance to replace all of the seals and gaskets
07-25-2001, 03:44 PM
#4
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Guess we are passing in our concerns. 
Yeah, I understand the crap jobs that the amatures do, or even the pros. I just don't think it is a big safety deal unless you are monkeying around with wheels or other critical parts.
I can't believe you said "wheels perhaps" with respect to polishing concerns. If anything deserves it, they do.
We should think about refinish of wheels and what to do if someone wraps a chain around the front A-arms to pull up on a flat bed and leaves nice impressions in the metal.
Yeah, I understand the crap jobs that the amatures do, or even the pros. I just don't think it is a big safety deal unless you are monkeying around with wheels or other critical parts.
I can't believe you said "wheels perhaps" with respect to polishing concerns. If anything deserves it, they do.
We should think about refinish of wheels and what to do if someone wraps a chain around the front A-arms to pull up on a flat bed and leaves nice impressions in the metal.
07-25-2001, 04:29 PM
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Yeah, I cannot believe I said "perhaps" either. I was kind of thinking that most folks at least clearcoat their wheels when they polish them, which at least adds some protection.
And I don't really think a cracked manifold is safety issue as much as it is a bummer to have one crack. And you know, it really only cracks to where you can just see it. Not a problem for most, but for someone who wastes the time polishing you can pretty much assume they will notice it in a heartbeat.
And I don't really think a cracked manifold is safety issue as much as it is a bummer to have one crack. And you know, it really only cracks to where you can just see it. Not a problem for most, but for someone who wastes the time polishing you can pretty much assume they will notice it in a heartbeat.
07-25-2001, 04:37 PM
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Hey Rick. That was a tongue in cheek response right?
The reason I commented on the aircraft skin is to point out that the strength layer is protected by pure AL, which can be polished since it is not susceptible to the same corrosion as alloyed AL. This is why you see polished aircraft.
The reason I commented on the aircraft skin is to point out that the strength layer is protected by pure AL, which can be polished since it is not susceptible to the same corrosion as alloyed AL. This is why you see polished aircraft.
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07-25-2001, 10:23 PM
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Manning, you forgot some of the benefits of polishing aluminum like its ability to reflect radiant heat.You also stated that you would be concerned about polishing an intake manifold because it could develop cracks or breaks,etc.......Well I can tell you that this is not the case.The intake manifold is pretty thick(1/4" at least) to begin with.Very little material is removed in the polishing process so it does not take away from the structural integrity of an intake manifold or cam housing in any way whatsoever.I have had both of these things polished for years with no adverse effects.The finish is still good too even though it was never clearcoated or anodized after the polishing process.As far as breathing compounds and aluminum dust goes.....It is a health hazzard.If you are going to polish your parts yourself, you should take precautions so you can avoid hurting yourself or the enviroment.Eye protection and a dust mask are a must!
Tim
86 951 http://www.speedforceracing.com
Tim
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07-26-2001, 02:16 PM
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I can't speak to what polishing can do to the integrity of the metal, but IMHO it looks poser and overdone. I like to leave the Polish to the Asian cars, Polish does not product HP or make the car handle better.
As for heat reflection... give me a break, Guys polish to show off not cool the car down. I have installed plenty of superchargers and turbos and have not ever heard heat reduction as a selling point for polishing.
As for heat reflection... give me a break, Guys polish to show off not cool the car down. I have installed plenty of superchargers and turbos and have not ever heard heat reduction as a selling point for polishing.
07-26-2001, 06:35 PM
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I was only pointing out that there are some benefits to polishing besides looking good. Someone made a point to post about the drawbacks, so I figured why not post the benefits?
One of the main reasons I polished the parts on my car was to avoid having a grimey looking engine bay.Mine looked bad when I got it and cleaning proved to be futile.Let me tell you,trying to clean years of grease and grime off a cast intake manifold or cam housing is a real bitch.Now....If I get stuff on my intake, I just wipe it off. If the finish starts to fade I just use some aluminum polish to bring out the luster.Overall, I am happy with the way it looks, the ease of maintenance and the response I get from people who see it.
Whether you like it or not is your opinion.However, I would definitely think twice about calling me a poser because of it.I am far from a poser and I think 420 horsepower and 450 ft/lbs of torque (that was put together with my own hands) proves it.Take care.
Tim
86 951 http://www.speedforceracing.com
One of the main reasons I polished the parts on my car was to avoid having a grimey looking engine bay.Mine looked bad when I got it and cleaning proved to be futile.Let me tell you,trying to clean years of grease and grime off a cast intake manifold or cam housing is a real bitch.Now....If I get stuff on my intake, I just wipe it off. If the finish starts to fade I just use some aluminum polish to bring out the luster.Overall, I am happy with the way it looks, the ease of maintenance and the response I get from people who see it.
Whether you like it or not is your opinion.However, I would definitely think twice about calling me a poser because of it.I am far from a poser and I think 420 horsepower and 450 ft/lbs of torque (that was put together with my own hands) proves it.Take care.
Tim
86 951 http://www.speedforceracing.com
07-26-2001, 09:00 PM
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Tim,
My comments are to point out that people are not polishing engine components to cool them down. Ease of cleaning has some merit. The majority of polished components don’t show up at your local track or performance driving event. These parts show up at custom car shows, and are used to get attention. The implication that it will keep things cooler to the point of making a performance enhancement would be stretching a bit.
I am sorry if you took my opinion personally, but I was clear at the beginning it was my opinion. I have no idea what your car looks like, or what you may or may not have polished.
My comments are to point out that people are not polishing engine components to cool them down. Ease of cleaning has some merit. The majority of polished components don’t show up at your local track or performance driving event. These parts show up at custom car shows, and are used to get attention. The implication that it will keep things cooler to the point of making a performance enhancement would be stretching a bit.
I am sorry if you took my opinion personally, but I was clear at the beginning it was my opinion. I have no idea what your car looks like, or what you may or may not have polished.
07-27-2001, 03:07 AM
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I didnt really take it personally. I knew what you meant. I was just having a little fun;^) Afterall.... I think you misinterpreted what I said. Do not get me wrong, I am not trying to say polishing does this or that for performance.It does help reflect radiant heat.Does that add horsepower? I cannot say for sure but I seriuosly doubt it.What I do know is that polishing some of these non critical parts is not going to compromise their structural integrity. BTW, here is a pic of my engine bay since you havent seen it.
Tim
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07-27-2001, 12:46 PM
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I, for one, hate those polished asian cars at all those stupid car shows...
But I think TurboTim is the man. That just looks tight, and on top of all that his car is a rocket built by him and him alone (and Hans and Fritz in Stuttgart some 13 years ago of course).
Good job Tim I think it looks great. And as I told you before, I'll be contacting you as soon as I get my 951 (whenever that may be) to spend a little hard earned money...
-Matt
But I think TurboTim is the man. That just looks tight, and on top of all that his car is a rocket built by him and him alone (and Hans and Fritz in Stuttgart some 13 years ago of course).
Good job Tim I think it looks great. And as I told you before, I'll be contacting you as soon as I get my 951 (whenever that may be) to spend a little hard earned money...
-Matt
07-31-2001, 01:29 PM
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Tim,
I am with you on the polished looking pretty good argument, and it is most definitely easier to clean, but I am not too sure about the reflecting heat issue.
Obviously polishing the inside of the intake helps.
Regarding the fact that polishing without protecting the resulting surface can compromise the integrity, this is due to exposer to the elements causing intergranular corrosion, not because you have removed too much material. And I have seen small crack develop at the flanges after polishing. Not right away, but it did happen. Is it a safety issue? No. Does it look dopey? Yes.
By the way, did you get the drawing of the flange I e-mailed to you?
I am with you on the polished looking pretty good argument, and it is most definitely easier to clean, but I am not too sure about the reflecting heat issue.
Obviously polishing the inside of the intake helps.
Regarding the fact that polishing without protecting the resulting surface can compromise the integrity, this is due to exposer to the elements causing intergranular corrosion, not because you have removed too much material. And I have seen small crack develop at the flanges after polishing. Not right away, but it did happen. Is it a safety issue? No. Does it look dopey? Yes.
By the way, did you get the drawing of the flange I e-mailed to you?
