radiators-Aluminum vs. copper 6

[JayMaechtlen]

What are the pros and cons of Aluminum ratiators versus brass radiators?



Jay Maechtlen

 

[kenvlach]

daubery,
I appreciate your many contributions, but don’t fully agree on the painting:
1) Corrosion of Al can be worse than Cu in northern climes where salt is used to de-ice roads. Many Al radiators are painted.

2) Rather than the thick, gloppy paint that you describe, manufacturers use thin gloss [prettier & stays cleaner than flat black] black lacquer or polyurethane on radiators. E.g., GM Satin Black (SP139), a polyurethane. “Most engine paints are too thick for radiator use because they can interfere with the heat transfer and block airflow between the cooling fins. This factory-finish aerosol withstands high heat and is just the right gloss and thickness to match most OEM finishes, and is ideal for radiator applications. It is 550ºF (287ºC) chemical resistant.”

3) To avoid the incomplete coverage: “Electrophoretic coating, which is already widely used for auto components, enhances external corrosion protection by providing an even distribution of paint throughout the entire radiator, including all the innermost parts…Electrophoretic coating strengthens the radiator even further by providing maximum corrosion protection in every nook and cranny of the core with little or no addition to the overall weight of the radiator and negligible effect on heat transfer.”

http://automotive.copper.org/no-flux.html

4) Maybe unscientific, but here “The [Al] radiator core was painted with a thin coat of flat black paint, the better to radiate some of the heat.”

http://www.sandsmuseum.com/cars/seven/myseven/radiator/radiator.html

5) For balance: a totally pro-Al radiator site. Even they paint as part of detailing [to match OEM Corvette]: “Every replacement aluminum radiator sold today comes bare aluminum. To keep our product on the same level, we offer a lower cost 941 with a base price and option to detail the radiator for high level shows. All other models include detailing in the price. Detailing includes, painting the radiator a black semi-gloss epoxy base paint, stamping the GM part number and date code, Harrison label, ink stamp, and the correct aluminum drain valve assembly.”

http://www.corvettepartsman.com/dewitt-faq.htm

 

[daubery]

Hi kenvlach,

Thanks for your reply... I will respond point-per-point below:

1) Salt-corrosion is certainly an enemy of any radiator - aluminium, or copper, no question...in USA, Russia, you name it...

Aluminium radiator manufacturers can use superior fins, which control the mode of corrosion a little better... The issue with paint, unless the part is completely dipped, is that some parts are not completely covered... these become preferentially-corroded...

Bare copper suffers the same fate... Salt is terrible stuff...

2)I am not refering to any specific paint at all... goop, or gloss, will ALL be subject to selective-coating, hence induced selective corrosion potential... The issue of importance would be the 'coating thickness'...

3) "Electrophoretic coating" - nice idea (works wonderfully), but WAY, WAY TOO EXPENSIVE... This idea was mooted by the ICA many years back, & still is, but the 'cost-penalty', in practice, proved to be way too prohibitive.

4) Radiation heat-transfer really only 'kicks in' at reasonably high temperatures - do the sums, if you don't believe me. For radiators, it has negligible effect & is not even considered by most serious designers of Automotive Heat-Transfer Devices... (I will do some basic calculations & post them to the board for your information...)

Regards,

Des Aubery...
(adTherm Technology -

http://www.adtherm.com

- info@adtherm.com )

 

[daubery]

Hi 'kenvlach',

I would also like to update & an earlier posting you made regarding the CuproBraze Process & correct a number of your statements. (Please don't take offence, but I would like to set the record straight on a number of technical issues).

1. >>Quote: “CuproBraze is the name of a new manufacturing process for copper-and-brass automotive radiators. The process uses fluxless lead-free brazing..."

Answer: The CuproBraze Process is NOT a fluxless process, as a small amount of flux additives have to be included in the tube-to-header slurry/paste to prevent the 'de-wetting' phenomenon, & porous joints. In addition, the binders which burn off during the brazing process contribute to environmental load.

--------------
2. >>Quote: "to produce new thin-walled radiators that perform better than thicker-walled aluminum products."

Answer: In general, the CuproBraze radiator can only perform better than a 'poorly designed' Aluminium Radiator... despite all the marketing hype to the contrary...

--------------
3. >>Quote: "The new radiator was developed by the International Copper Association and produced initially by the Universal Auto Radiator Manufacturing Company. They are typically 30% to 40% lighter than traditional copper and brass models, can be made smaller than their aluminum counterparts, and can provide up to 30% less air-side pressure drop. The CuproBraze process also shortens manufacturing time and reduces production costs.”

Answer: Most of this information is from ICA marketing literature from a few years ago (1998/1999)... In practice, these original claims were never upheld in the real world. 'Universal Auto Radiator' is now bankrupt & no longer operates.

----------
4. Quote: “Cost-Efficient CuproBraze® Radiators Show Superior Durability in Road Tests..."

Answer: This claim is, in general, unsubstantiated in practice...

---------
5. Quote: "…In addition, CuproBraze radiators can be made smaller in size, or with significantly higher heat transfer efficiency than aluminum models. The CuproBraze process offers further advantages over standard aluminum radiators, such as greater fuel economy, lower air side pressure drop, lower cooling module costs and weight, and less parasitic engine losses….”

Answer: Again, these claims are, in general, unsubstantiated in practice...

----------------------
6. Quote: “Commercial Production of CuproBraze® Radiators Begins Over 90 different models to be offered in 2000
The CuproBraze® revolution in automotive radiators has begun. Universal Auto Radiator Manufacturing Co. in Pittsburgh, Pennsylvania, USA, became the first company in the world to begin full production of the new CuproBraze radiator."

Answer: Again, UAR is out of buiness (for almost 1 year, now)

--------------
6. Quote: "...the CuproBraze® alloy can be HF (high frequency) welded; ultrasonic weldability had been mentioned as an advantage for Al by Peter7307. See
“Berry Radiateurs Adopts CuproBraze Process and Begins Production”

Answer: HF welding of 85/15 CuproBraze Brass has a lower thickness of around 0.110mm. In many cases, this is not thin enough to save cost over an equivalent Aluminium tube.

--------------
7. Quote: "It appears that CuproBraze® has given Cu the competitive edge over Al in the radiator & HXer market."

Answer: This was the marketing hype we (me included) used to market CuproBraze in the early days. In practice, the expected results have, unfortunately not been achieved...

Regards,

Des Aubery...
(adTherm Technology -

http://www.adtherm.com

- des@adtherm.com )



Best regards,

Des Aubery...
(adTherm Technology -

http://www.adtherm.com

- info@adtherm.com)

 

[daubery]

Hi 'stewbing',

>>Quote: I had heard something about adding a small elctrical charge to an aluminum radiator to prevent corrosion. I know that boat endines and gear often have a zinc plare bolted to them for a similar reason. How does this work?

DA: The zinc plate/block in a marine HX acts as a sacrificial anode which corrodes before the brass components are attacked. This is generally to stop de-zincification of the brass HX components... I have seen the effects of missing blocks & stray electrical currents in marine HX's - the brass tubes are destroyed in a few weeks... On a marine HX, the corrosion effect is more of an overall 'global effect' because the side of the HX subject to the most corrosion, is fully emersed in the sea water.

The small electrical charge to the aluminium radiator would be an attempt to try & prevent galvanic corrosion occurring... but, since, on a radiator, the galvanic corrosion occurs 'in local corrosion cells' it would be difficult to expect a 'globally applied' electrical current to sort this out. This is because the air-side of the radiator (most subject to corrosion) is NOT fully emersed in a liquid media - forcing the corrosion cells to be 'local cells'...

I hope that this explanation helps...


Best regards,

Des Aubery...
(adTherm Technology -

http://www.adtherm.com

- info@adtherm.com)

 

[Metalguy]

It can be done. Some years ago I attended a corrosion conference where a paper was presented on a small impressed-current device for this purpose. Idea was scrapped because it would have had to be manufactured for something like $2 in order for the "car companies" to use it.

So for now, just keep your cooling system full of 50/50 demin. water and a low-phos. silicate-free (and whatever else is new) antifreeze mix, and change it every 2-3 years or so.

 

[daubery]

This impressed-current device was no doubt attempting to protect the water-side of the radiator/engine cooling circuit... As Metalguy states, the antifreeze mix will keep that under control.

I was refering to the air-side corrosion in my previous posting...

One must never forget that there are always two sides to protect.


Best regards,

Des Aubery...
(adTherm Technology -

http://www.adtherm.com

- info@adtherm.com)

 

[TChronos]

Am I correct in thinking that the radiator should be electrically isolated to avoid corrosion? A manufacturer of racing radiators suggested to me that the radiator be grounded, but this doesn't seem right.

 

[daubery]

Hi 'TChronos',

>>Qupte: Am I correct in thinking that the radiator should be electrically isolated to avoid corrosion? A manufacturer of racing radiators suggested to me that the radiator be grounded, but this doesn't seem right.

DA: I beleive that grounding could prevent 'stray current' passing through the radiator & causing additional electrical effects, over-&-above the galvanic effects already present due to the differing 'galvanic potentials' of the different metals used. Perhaps, it would also ensure that all parts of the coolant loop are at similar ground voltage...

The 'corrosion micro-cells' I was refering to occur due to local 'galvanic differences' between materials - eg. fin/braze/tube joint - all different. The differences will determine which material is preferentially corroded - on the airside of the radiator.


Best regards,

Des Aubery...
(adTherm Technology -

http://www.adtherm.com

- info@adtherm.com)

 

[TChronos]

Here's where I'm puzzled...the source for stray current would be the block, with the coolant itself acting as an electrolyte. Current would end up finding ground through radiator if it was grounded. Any spot in the radiator that was slightly more anodic would tend to become the grounding point. I would expect the result to be one or multiple pinhole leaks.

On the other hand, if the radiator was well insulated from ground, it simply wouldn't be part of the circuit.

 

[daubery]

Hi 'TChronos',

>>Quote: ...the source for stray current would be the block, with the coolant itself acting as an electrolyte.

DA: The block acts as a source of Zinc & is preferentially corroded. This prevents de-zincification of the INSIDE of Brass tubes of the radiator. The effect of this zinc block on the whole radiator/pump/head circuit - I haven't thought about...

As I said before, the zinc block idea works with great success in marine HX's - eg. oil coolers - with oil on the outside of the tubes - sea water inside the tubes... The velocity of flow in the entry section of the tube causes eddies which tend to erode this section of the tube... If the tubes are not protected, this activity seems to leach out the zinc very rapidly - hence the additional protective source of zinc block.

--------------
>>Quote: Current would end up finding ground through radiator if it was grounded. Any spot in the radiator that was slightly more anodic would tend to become the grounding point. I would expect the result to be one or multiple pinhole leaks.

On the other hand, if the radiator was well insulated from ground, it simply wouldn't be part of the circuit.

DA: In my experience with Aluminium radiator tubes, the vast majority of problems occur on the airside of the HX. (In Japan, some radiators are manufactured with double-clad tubes, for additional pitting protection of the tube internals. This is said to be because of the poor quality of Japan's water.)

For airside corrosion of radiators, with large grain sizes in the tubes, if pitting corrosion does begin, there is quick pin-holing of the tube... Thus, the fin material is selected to be sacrificial to the tube - preferably with a 'onion-peeling effect' of the fin (controlled corrosion), in such a way as to protect the tube. Hence the use of Zinc-rich aluminium fins.

On Aluminium condensers, the galvanics become crazy after brazing & the extruded tubes & manifolds can be quickly corroded, if suitable zinc-rich fins are not selected (at least this is my experience).



Best regards,

Des Aubery...
(adTherm Technology -

http://www.adtherm.com

- info@adtherm.com)

 

[Metalguy]

Daubery,
Yes, as you said, I was only referring to the inside of the rad. I wrote my response when you were writing yours, but you hit the &quot;send&quot; button first. <g>

I wasn't aware of airside corrosion, but I can see why it could rapidly pit tubing. While driving along, the rad. is fairly hot, and in wet conditions there must be a lot of wetting and drying cycles. Such cycles concentrate all the harmful impurities like Cl, and corrosion rates can double for every 10 deg C (18 F) rise-if some other mechanism doesn't change things. So, at a rad. outside temp. of 80C the corr. rate *can be* 64 times faster than at 20C!

Also, for non-salt water internal use, Mg anodes are better than Zn for protecting Al. They will also protect Zn.

But if I were buying a RR or $$$ equiv., I'd want a nice Ti unit (and bigger is better!).

 

[daubery]

Hi 'MetalGuy',

Thanks for your posting...

Wow... That corrosion rate is frightening - but it definitely occurs in practice. I have seen pictures of Russian uncoated Aluminium radiators after 1 season of operation in the Russian Winter - you can push your hand right through them... A total disaster - no wonder they began coating them...

Best regards,

Des Aubery...
(adTherm Technology -

http://www.adtherm.com

- info@adtherm.com)

 

[kenvlach]

So many comments about corrosion of radiators – it seems surprising that our cars and trucks can even run!!!

1) I had mentioned earlier the nasty effect of salt on Al radiators, a major factor in OEM’s having them painted. The effect of salt on copper and copper alloys is much less – saltwater evaporators often use Cu alloys rather than stainless steel.
2) Radiator mounts and straps include rubber for electrical isolation, to prevent galvanic corrosion with the steel frame.
3) An applied electrical charge to the outside of a radiator does no good (except when wet).
4) Neither a sacrificial anode (Mg or Zn) nor an applied cathodic electrical charge to the inside of a radiator will give much protection beyond a very limited area. The protection will not extend done the tubes (unless you can connect and run a network of anode wires down the tubes without shorting!). Perhaps you guys should do some electroplating and anodizing to learn how the current density drops off with distance inside holes.
5) Aluminum brazing actually comes closer to welding in terms of composition and temperature than other metals. There shouldn’t be much galvanic corrosion. CuproBraze® achieves something similar for Cu alloy – gets rid of the solder, which is both a mechanical and corrosion weak point (as I had also mentioned previously).
6) For protection of Al radiators exteriors, an alternative to painting is anodizing. Thinner and protective. Navy submarines use anodized radiators for liquid-to-seawater cooling. The anodize develops pits after about 1.5 years, then is ‘slow-stripped’ and re-anodized.

An automotive radiator given reasonable care should last the lifetime of the vehicle in normal usage. Additional washings will help where salt is used on the roads in winter.

 

[finman]

During my time running a Nocolock Brazing plant, non of our units were painted, all were supplied in the natural condition. The Nocolock flux provides a good anti corrosion barrier after the braze process. This coupled with the use of a layer of non corrosive aluminium on the inside of the tubes and headers ment we didn't suffer any major problems.

Our units had been tested by many of the OEM's and the M.O.D. for performance, mechanical strength and corrosion without a problem.

It maybe that the Cupro-Braze suppliers saw a diminishing busines with the Copper/Brass/Lead materials both on cost and environmental issues and needed something to reinstate themselves into the market due to the defection to Aluminium by the majority of radiator producers.

Alot of the claims made for Cupro-Braze are ambiguous or generalisations which are little more than sales B.S. but I still believe that CB has a place in the market.

 

[daubery]

Hi 'Finman',

>>Quoteuring my time running a Nocolock Brazing plant, non of our units were painted, all were supplied in the natural condition. The Nocolock flux provides a good anti corrosion barrier after the braze process. This coupled with the use of a layer of non corrosive aluminium on the inside of the tubes and headers ment we didn't suffer any major problems.
Our units had been tested by many of the OEM's and the M.O.D. for performance, mechanical strength and corrosion without a problem.

DA: This has been my typical experiences with both Nocolok & Composite Deposition (CD) Technology... The Nocolok wasn't perfect, but generally good enough for most applications. I believe that the painting is really only for the 'extreme' corrosion applications.

------------
>>>Quote:It maybe that the Cupro-Braze suppliers saw a diminishing busines with the Copper/Brass/Lead materials both on cost and environmental issues and needed something to reinstate themselves into the market due to the defection to Aluminium by the majority of radiator producers.

DA: Aluminium brazing entered that Automotive Heat-Transfer market with a superior product in terms of 'Specific Power' & advanced lightweight radiator designs. It was soon killing the sale of Copper & Brass radiator strip. The Copper producers & Strip Manufacturers (no names mentioned) felt that they had to counter this threat to their business... At that time it was basically considered that Aluminium would eventually 'kill' copper-brass radiators & that a 'brazing technology' for Copper-Brass had to be developed. The 'CuproBraze Technology' was originally developed in the USA by the ICA, in parallel with research being performed by the largest copper/brass radiator strip supplier in the world - in Sweden (again, no names). This process limped along for some 8 years, before I joined began assisting the Swedes as an Executive Technical Consultant... My brief was to build a team & to assist the comercialisation of the CuproBraze Process.

I travelled the world; built the team; generated Technology Vision; Technology Marketing Strategies; & then helped the Swedes to implement them - Asia was the main thrust of my endeavours. We had great success in interesting the Asian auto market.

In parallel with the marketing I pressed for rapid Technical Development in order to leapfrog the new technology ahead of Nocolok... We began to have success & then the internal politics & petty jealousies within the Swedish group became too much for me... I resigned, & we back to assisting them on a part-time consulting basis.

---------------------
>>>Quote:Alot of the claims made for Cupro-Braze are ambiguous or generalisations which are little more than sales B.S. but I still believe that CB has a place in the market.

DA: Absolutely true - they are ambiguous & always will be, because the real intrinsic Technical Capability behind the CuproBraze Technology is NOT WELL ENOUGH DEVELOPED... I had set forward clear Technology Roadmaps & Strategies that would pull it ahead of Nocolok - but the internal politics have basically slowed all USEFUL new developments to a grinding halt...

----------
This is why I started my new 'hi-tech' company - 'adTherm Technology' to serve as a technical sprinboard & to answer at a fundamental level if CuproBraze could ever seriously compete with Nocolok... My answer lies in my discoveries with the 'Specific Power' of the fins... See my earlier posts... Copper-Brass is not viable, unless 'radical' fin designs are used... it becomes far too complex...

IMHO opinion, CuproBraze does not have sufficient knowledgable technical resources to be able to adequately support the high-volume production of Copper-Brass HTD's - other than for a small number of factories - it is also beginning to lose ground to Aluminium again as far as costs are concerned...



Best regards,

Des Aubery...
(adTherm Technology -

http://www.adtherm.com

- info@adtherm.com)

 

[Metalguy]

Kenvlach,
Your post made me think back a little harder to that corr. conf. You're correct, of course. What was being presented wasn't a CP system, but an electronic corrosion-potential *monitoring* system. Sorry for the brain-fade, hope it ain't perman--er, what's the subject again?

 

[finman]

Hi Des

It seems that we have alot in common! I have been frustrated for years by the lack of research companies put into fin design, I'm convinced that the humble fin is the key to significant improvements. I can appreciate the concept of Fin Specific Power although not an academic myself I would be hard pushed to determine the figures. I have always been the man who makes fins &quot;The Finman&quot; and my motto has always been if you can dream it, I can make it.....

 

[daubery]

Hi 'finman',

>>Quote: Hi Des
It seems that we have alot in common! I have been frustrated for years by the lack of research companies put into fin design, I'm convinced that the humble fin is the key to significant improvements. I can appreciate the concept of Fin Specific Power although not an academic myself I would be hard pushed to determine the figures. I have always been the man who makes fins &quot;The Finman&quot; and my motto has always been if you can dream it, I can make it.....

DA: The multi-louver fin design has the highest impact on the heat-transfer of Automotive Heat-Transfer Devices (HTD's). Current technology is essentially refined versions of a technology that was originally introduced around 50 years ago.

There all types of speculation about how these fin work - what factors are important - louver angle, louver pitch, fin thickness, fin height, louver length, fin pitch... you name it... How to link these all toghether to provide optimum designs - most folks have absolutely no clue...

The reason - it is impossible to find small-enough temp sensors to insert into these tiny spaces, to accurately profile the air temperatures within the fins.

This is the reason I have developed the 'Virtual Wind-Tunnel Concept' at adTherm Technology... It is to allow designers to test proposed fin designs, & to predict the performance... It entails a combination of CFD & proprietary software to map the flow regime within the fins themselves... Take a look at the adTherm website (

http://www.adtherm.com)

for a sneak preview of the next generation of design tools...



Best regards,

Des Aubery...
(adTherm Technology -

http://www.adtherm.com

- info@adtherm.com)

 

[turbododge]

From what I have seen, it is very difficult to directly compare most aluminum and copper/brass radiators. I have a very difficult cooling job on a twin turbo 340cid V8, that has a fully packed engine compartment and not a lot of space for a radiator. I have tried several versions of both copper/brass and aluminum, and I think the design differences had more to do with the results than the materials.

Here is what I found:

3 core copper/brass cooled well at speed, not well at idle

4 core copper/brass cooled better at idle, but worse at speed than the 3 core

Single (1.25&quot core aluminum, cooled OK at speed and not well at idle

2 core (1.25&quot;X 2) aluminum cooled extremely well at speed, and a bit better at idle than the single core.

I would rate them this way:

At speed from best to worst 1. two core aluminum 2. 3 core copper/brass 3. tie between single core aluminum and 4 core copper/brass

At idle from best to worst 1. 4 core copper/brass 2. tie between 2 core aluminum and 3 core copper/brass 3. Single core aluminum

The results lead me to believe that how the tubes and fins are laid out, and how dense they are, make more difference than what they are made of. The radiators that had the lesser resistance to airflow, because of less fins and/or thickness, did better at speed because they allowed more airflow through the radiator. The radiators that did best at idle, had more fins and/or thickness, that could dissipate the heat better at the low airflow rates at idle.

The aluminum radiators use big tubes and wider spacings of tubes and fins, so they can allow a lot of air through. If you can supply the air, they will cool extremely well. The copper brass use smaller tubes (burst strength issues) and high density finning, so they perform better at lower airflow rates, but you can't put enough air through them to get bigtime cooling.

My final solution was to use the 2 core aluminum radiator, which gave outstanding cooling at speed. To address the idle heat up issue, I made a pulley that would spin the fan at 1.3 times the speed I had, and added a viscous clutch to get rid of the added drag at speed. The extra airflow made the aluminum 2 core out perform all the others at idle.

If radiator manufacturers start telling you they cool &quot;X&quot; amount better than the competition, be sure to ask them what they are running for airflow velocity and static pressure drop though the radiator, and at what heat dissipation rate they are operating (to simulate idle, cruise, full power etc). Most either don't know, won't tell, or don't care because the numbers they are giving are bogus.

 

[kenvlach]

The remarks of daubery and finman demonstrate some basic truths: necessity is the mother of invention, competition improves the product – otherwise, mfrs. are content with the status quo, etc. Thanks for the Nocolock and CuproBraze© info and history. Too bad that progress is always impeded by petty politics, empire builders, etc. Dilbert, anyone?

turbododge, ‘shoehorning’ in an oversized engine created a greater cooling demand while simultaneously reducing airflow. In any event, your considerable industriousness shows that the engine and radiator have to be integrated into the overall vehicle design. A bigger radiator won’t help without increased air and coolant flow (presume your water pump speeds up with the fan). Two questions: 1) Have you done any sheetmetal work to direct air toward the radiator and out of the engine compartment? 2) Were your copper+brass radiators the conventional soldered type?

Maybe radiator salesmen don’t have much technical info, but I am certain that the radiator and vehicle mfrs. do have the ‘real numbers,’ e.g., per SAE J819 Engine Cooling System Field Test (Air-to-Boil), J1393 On-Highway Truck Cooling Test Code, J1994 Laboratory Testing of Vehicle and Industrial Heat Exchangers for Heat Transfer Performance, J1542 J1994 Laboratory Testing of Vehicle and Industrial Heat Exchangers for Thermal Cycle Durability, J2082 Cooling Flow Measurement Techniques, etc.

An interesting thread.