About Plating and My Engine Bay Cleaning

[thelews]

quote:Originally posted by mdsalemi
John, if you meant powder coat in general, well, it provides a surface that looks exactly like paint, at about the same cost, in the same available colors, but infinitely more durable.  The OEM wheels were originally powder coated, as were many parts.  If one considers re-painting some part (a battery hold down; a wheel; a fuel-pump cage; a suspension part) that can withstand the heat of the curing process, it's a better finish.  But you knew that.

I'm not convinced.  I know professionals who would not choose it (based on experience), it is not what the factory did (my 250 SL wheels are powder coated?)and it is not spot repairable for the inevitable wear, damage, etc. that will occur during driving or maintenance.  Today's quality epoxy paints are extremely tough, have a beautiful finish, are easy to spray (rattle cans), require no special equipment and can be scuffed and touched up should a need for repair or freshening occur.  In another car of mine, damage occured to the powder coated front subassembly.  No way to repair it other than repowder coat the whole assembly if a match is desired.  It was redone, but in epoxy paint so that the next time around a scuff, mask and spray while on the car is all it would have needed.

P.S. The previous meticulous owner of my car, refreshed the front sub and components after some cosmetic damage using the factory painting process.

[mdsalemi]

John,

If you don't like powder coat, don't use it.  Simple.

The OEM wheels (with the 108 part number) that came with my 280 were powder coated.  So were the aluminum replacements I installed.  Yes, I had them re-coated.  If you go through the car you'll find quite a few powder coated parts.  Modern cars, even more so.  In fact, a lot of formerly plated parts are now powder coated.  Have a drink to calm you down.

You don't have to like it, and if you choose to refinish things paint is always a viable option.

[thelews]

quote:Originally posted by mdsalemi

John,

If you don't like powder coat, don't use it.  Simple.

The OEM wheels (with the 108 part number) that came with my 280 were powder coated.  So were the aluminum replacements I installed.  Yes, I had them re-coated.  If you go through the car you'll find quite a few powder coated parts.  Modern cars, even more so.  In fact, a lot of formerly plated parts are now powder coated.  Have a drink to calm you down.

You don't have to like it, and if you choose to refinish things paint is always a viable option.

Don't need a drink, Michael, although you're welcome to buy me one anytime. Simply my opinion and experience in an ongoing debate amongst enthusiasts of vintage cars of all brands and models.  Powder coat for components and clear coat for paint are modern methods.  Nothing wrong with them.  I was offering the alternative view for members to consider, especially those seeking originality.  Absolutes of best, only, infinitely, etc. can be misleading.  Modern finishing methods are shades of gray and one should definitely choose what satisfies their judgment best.  Discussion of various viewpoints and shared experiences helps toward this end.

[wwheeler]

Michael,

Your comments about the plating and powder coating were very well put and I completly concur.

[wwheeler]

I have done an appearance comparison between golden cad plating and yellow chromated zinc plating. I just had my throttle linkages and relay support on the firewall professionally replated using golden cadmium. I have also plated many small things at home using a zinc plating kit and then coloring (chromating) to a yellow tint. Here are the appearance differences:

The golden cadmium has a rainbow effect on top of a gold opaque base. The yellow zinc also has a rainbow effect but the gold color is more transparent or clear. The look of the base gold color is the big difference.

I like to apply a thin satin gloss clear (Eastwood)to the plated surface to seal it and prevent fading. This clear will make the plating last a very long time and will be easy to clean. The downside to the clear is that it mutes the rainbow effect on both zinc and cadmium. The good news is that it brings the two types of plating closer in appearance.

As stated earlier, cad is more durable and correct than zinc. Since these linkages were too large for me to plate at home, I had them cad plated. Cad does not cost that much more than professional zinc plating but cannot be done at home because cadmium is highly toxic. However, taking small nuts and bolts to the plater can get expensive in a hurry and is a pain which is why I do them at home. For me, it is a compromise between corectness, durability, price and convienence. I always try to use the same plating system on mating parts so the appearance is consistent.

[Garry]

Hi Wallace,

I am interested in your comparisons as I have purchased a small home Zink Plate kit with chromate and propose to do some of the parts from the engine bay that way rather than fiddle around with a professional plater.
Did you finish off the clear in gloss, mat  or semi gloss/saturn finish and did you use a heat resistant paint?

Garry

[mdsalemi]

quote:Originally posted by wwheeler

I have done an appearance comparison between golden cad plating and yellow chromated zinc plating. I just had my throttle linkages and relay support on the firewall professionally replated using golden cadmium. I have also plated many small things at home using a zinc plating kit and then coloring (chromating) to a yellow tint. Here are the appearance differences:

The golden cadmium has a rainbow effect on top of a gold opaque base. The yellow zinc also has a rainbow effect but the gold color is more transparent or clear. The look of the base gold color is the big difference.

I like to apply a thin satin gloss clear (Eastwood)to the plated surface to seal it and prevent fading. This clear will make the plating last a very long time and will be easy to clean. The downside to the clear is that it mutes the rainbow effect on both zinc and cadmium. The good news is that it brings the two types of plating closer in appearance.

As stated earlier, cad is more durable and correct than zinc. Since these linkages were too large for me to plate at home, I had them cad plated. Cad does not cost that much more than professional zinc plating but cannot be done at home because cadmium is highly toxic. However, taking small nuts and bolts to the plater can get expensive in a hurry and is a pain which is why I do them at home. For me, it is a compromise between corectness, durability, price and convienence. I always try to use the same plating system on mating parts so the appearance is consistent.

Wallace,

It is important to remember--not so much for you but for everyone else without the direct experience either with the chemistry kits you are playing with or the professionals you have used, that the "gold" color applied is not a plating.  It is a reactive "phosphate wash" so to speak, that is created on top of the fresh zinc or cadmium plating, and isn't there for looks but for added protection.

I think that even when pros do it, there are differences in how the coloring looks.  The color comes from whether or not "Trivalent" Chromates are used, or "Hexavalent"; how many times the product is dipped; the thickness of the coating created, and the underlying color of the base plating.

The "gold cadmium" that I had done had not a whit of rainbow look to it; the silver cadmium (clear) was flat, too.  These were from Prime Plating.  But if you look at paint kits from Eastwood that want to mimic gold cadmium plating they are trying to achieve a mottled, rainbow look that you describe.

Check around and you'll see that many platers offer a variety of these protective finishes over their base plating; in addition to the traditional yellow, there's blue, black, olive drab to name a few.

[wwheeler]

Garry,

I used a clear paint from Eastwood called diamond coat(eastwoodco.com)and they have gloss or satin finishes in aerosol or brush-on. This clear is claimed to be good to 350 F. I goes on very thin and isn't noticeable once it is on. It does not have great scratch resistance which is similar to other paints. I used the satin finish and use it on almost all of my plated surfaces to further increase protection from the elements.

Micheal,

I did not ask for anything special when I got the parts plated with golden cad and the part did have a bit of rainbow color. I am not sure which chromate they used. You are correct about the yellow color not being just for appearance. It in fact helps protect the cad or zinc plating from acid attack. Cad, and more so zinc or prone to damage from even the mildest acids (coca-cola). The yellow acts as a shield.

[Longtooth]

Micheal.. I live in CA, SF Bay area, and Cad plating ain't to be found in these here parts that I've been able to find, nor others that are replating engine linkgages and other originally cad plated parts. Maybe CA's and MI's environmental or toxic / hazardous waste laws differ? or are enforced differently?

Yellow zinc chromate is used instead, as you say.  It may be possible to find out of state Cad plating sources... I haven't tried though.

I recently judged some show class, classic MB's, including a couple of W113's and a 300SL Coupe, and while I wasn't on the engine compartment judging team, at the judging rules meeting before hand it was stated that there were to be no deductions for yellow zinc Chromate vs Cad.... and the comment by the lead judge was that in CA it's rare if ever to see actual Cad plating anymore.  Just fyi... deductions for painted or clear-coated plated parts though... an authenticity deduction (50% of available points).  

[Longtooth]

I haven't seen anybody post yet about why MB didn't use highly polished alumimum valve covers, but maybe I missed it.  If not, the reason was and remains heat dissipation.  The non-polished surface emits more heat than polished surfaces... significantly so considering the difference in emitting surface area.  It's part of the W113's engine cooling "system".  Same applies to chrome plating engine compartment parts.. only even moreso.

[mdsalemi]

quote:Originally posted by Longtooth

Micheal.. I live in CA, SF Bay area, and Cad plating ain't to be found in these here parts that I've been able to find, nor others that are replating engine linkgages and other originally cad plated parts. Maybe CA's and MI's environmental or toxic / hazardous waste laws differ? or are enforced differently?

Yellow zinc chromate is used instead, as you say.  It may be possible to find out of state Cad plating sources... I haven't tried though.

I recently judged some show class, classic MB's, including a couple of W113's and a 300SL Coupe, and while I wasn't on the engine compartment judging team, at the judging rules meeting before hand it was stated that there were to be no deductions for yellow zinc Chromate vs Cad.... and the comment by the lead judge was that in CA it's rare if ever to see actual Cad plating anymore.  Just fyi... deductions for painted or clear-coated plated parts though... an authenticity deduction (50% of available points).  

Longtooth,

Most interestingly and coincidentally, contrary to your experience I'm sad to say, the two true cadmium platers I've spoken with and used are in California.

Burbank Plating http://www.burbankplating.com/  and
Prime Plating http://www.prime-plating.com/

[wwheeler]

Longtooth,

That is interesting and good information about the point standard for cad vs. zinc plating. Given the current enviromental positions, that seems fair. I also think that deducting points for clear coating and painted parts where not done by the factory is absolutely correct. Cars that are being judged to that degree, should be held to a higher standard. In my case, I don't intend on having my car judged and am sacrificing originality for longevity.

Thanks for the info!

[Mark280SL]

I just found it very interesting that a polished valve cover will not emit as much heat as a non polished one one. Why is this? Does the polishing compound seal it somehow or the abrasive action of polishing on the metal create a less porus surface that then holds in the heat?

quote:Originally posted by Longtooth

I haven't seen anybody post yet about why MB didn't use highly polished alumimum valve covers, but maybe I missed it.  If not, the reason was and remains heat dissipation.  The non-polished surface emits more heat than polished surfaces... significantly so considering the difference in emitting surface area.  It's part of the W113's engine cooling "system".  Same applies to chrome plating engine compartment parts.. only even moreso.

[thelews]

quote:Originally posted by Mark280SL

I just found it very interesting that a polished valve cover will not emit as much heat as a non polished one one. Why is this? Does the polishing compound seal it somehow or the abrasive action of polishing on the metal create a less porus surface that then holds in the heat?

My valve cover is polished.  In the hottest weather the temp barely rises above 180.

[psmith]

quote:Originally posted by Mark280SL

I just found it very interesting that a polished valve cover will not emit as much heat as a non polished one one. Why is this? Does the polishing compound seal it somehow or the abrasive action of polishing on the metal create a less porus surface that then holds in the heat?

As LT said, the smooth surface has less surface area than the rough one.

[Mark280SL]

I guess I must be thick, how can it have less surface area if it's polished? surface area would not be changed by polishing or anything else for that matter unless what we're saying is polished vs unpolished areas, is that it?

[Rolf]

The smoother the surface the less nooks and crannies it has.Polishing a surface smooths the high points of a surface so the high points become less; therefore less surface.

[thelews]

quote:Originally posted by Rolf

The smoother the surface the less nooks and crannies it has.Polishing a surface smooths the high points of a surface so the high points become less; therefore less surface.

If you had to quantify that percentage of greater surface vs. polished, what would be your guess?  Or, what percentage of surface is polished off of the cover?


By the way, Peter, this is why we use quotes...so we know who is being spoken to and with respect to what issue.  I'm the first to reply to Rolf's comment above.

[Mark280SL]

I thought about that but on an object as small (relatively speaking) as the valve cover that is already very smooth to begin with (at least mine is) I'm surprised that the polishing could reduce the surface area more then an insignificant amount and therefore affect its ability to cast off heat. Live and learn.

quote:Originally posted by Rolf

The smoother the surface the less nooks and crannies it has.Polishing a surface smooths the high points of a surface so the high points become less; therefore less surface.

[Rolf]

I was just making a general statement regarding what Mark had questioned about how an area could haveless surface area if polished. I agree that the surface area on the valve cover, when polished, should not change significantly enough to have any effect on the temp.

[thelews]

quote:Originally posted by Rolf

I was just making a general statement regarding what Mark had questioned about how an area could haveless surface area if polished. I agree that the surface area on the valve cover, when polished, should not change significantly enough to have any effect on the temp.

I appreciate your response and it's pretty much the answer I expected.  What you explained made perfect sense, but from a practical point of view didn't seem significant enough to make a difference in temp.

[Longtooth]

Micheal, I stand corrected re: CA Cadmium plating facilities.  Thank-you for the web-sites.  The local (Santa Clara Co.) facilities have been telling me they had to stop Cad plating due to EPA or Hazardous waste rules... sounds like they meant they couldn't afford to comply in our area.  One of the ones that shows up in NorCal (Santa Clara) on googleing for Cadmium plating actually doesn't do it anymore.  There are a plethora of them in SoCal though, so I guess there's some kind of industry that needs it down there ... marine? air-craft?


Anyway, thanks. I'll have to spend more time looking in our area next time I decide to get some Cad plating done.

[Longtooth]

Regards cooling capacity of a smooth/polished v rough finish, the area of a rough surface is approximately 1.5x (practical) to 2x (idealized) that of a highly polished surface. See attached diagram --- an isoscelese triangle type surface finish would actually have more than 2x the surface area of a smooth (highly polished) finish in the idealized case.  

Furthermore there are 2 types of heat dissipation involved... radiant and convective (i.e. air movement over surface)... in either case (rough or smooth).  However, radiant energy passing from the inside of the metal to the outside is affected by the interface between the internal volume and the external surface.  The more highly reflective the external surface, the more the heat passing from the inside to the external surface is reflected back onto itself.. and less escapes.  This is also true with highly thermally absorbant surfaces vs highly thermally reflective ones.  Thus, black bodies radiate more heat than white bodies.  That is to say that if the external surface is painted black or has a black oxide coating it will radiate more heat than the white surface.... even though the convective dissipation will be the same.


Download Attachment: Surface Area - Rough v Smooth.JPG
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