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Cylinder heads? who cares I have shiny coolant pipes!
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240Gordy
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PostPosted: Mon Jan 25, 2010 9:37 am    Post subject: Cylinder heads? who cares I have shiny coolant pipes! Reply with quote

Loogy pointed out a potential problem with stainless steel coolant pipes on a thread here,

loogy wrote:
This is NOT a knock on any vendor for selling the product, but I will NEVER install stainless cooling tubes on any of my vans. The answer as to why can be found here.

http://www.thesamba.com/vw/forum/viewtopic.php?t=218412&highlight=galvanic


here is the previous post that he made on the subject, which few posters bothered to read,

loogy wrote:
Terry Kay wrote:
The plain jane steel coolant pipes would have been more guilty of causing an electroletical reaction in the aluminum than the stainless pipes.

A good grade of stainless won't hurt your Van or the engine.


Really?

The galvanic voltage aluminum is 0.70-0.90
The galvanic voltage for steel is 0.60-.070
The galvanic voltage for 300 series stainless is 0.00-0.15

In order to prevent or reduce galvanic corrosion, the galvanic voltages of the dissimilar metals need to as close as possible to each other. In the galvanic series, the metals with the higher voltage potential (aluminum in this case) becomes the anode when coupled with with a metal of lower voltage potential and therefore corrodes faster that it would if it were all by itself. Looking at the numbers above, it is clear to see that aluminum has a much closer potential to steel than it does to stainless steel.

Mild steel welded to stainless steel rusts (corrodes) much quicker than mild steel by itself for the exact same reasons, the large differences in galvanic potentials between the two metals.

Terry Kay wrote:
This is why all food processing plants,& milk production facilities use stainless tubing, tanks, vats, etc.

kayakwesty wrote:
it's why we use stainless steel in our nuclear plants, it's not affected by much.

you are worrying about nothing


Yes, but those facilities are made up almost entirely of stainless, not a stainless/aluminum mix therefore little or no galvanic reactions.

As far as the coolant being an electrolyte, it can most certainly. All it needs is a small electrical leak connected to the engine. Vanagons are obviously notrorious for ground and electrical issues so a small electrical leak could easily go unnoticed. Even if there were no electrical leaks, if the coolant is broken down too severely or mixed with water that has a high mineral content, it becomes an electrolyte very easily. The introduction of exhaust gases into the cooling system will break down the corrosion inhibitors in the coolant very rapidy allowing the coolant to become an electrolyte. Vanagons are also notorious for head sealing issues.

Provided none of the above applies, the corrosion inhibitors in the coolant will break down in time allowing the galvanic corrosion process to eat your engine alive if you fail to keep up on your maintenance. Yes, the same could be said for a system with steel or other kinds of coolant tubes but the galvanic difference between aluminum and stainless is so much greater than steel and aluminum that the corrosion process will progress much faster.

Stainless is simply not the correct choice for cooling tubes on an aluminum engine. It's great for keeping the outside looking pretty but the potential damge that it can cause to the engine are not worth it. Not to me anyway.


and a further great post by Vanagoneer about corrosion, and mitigation,

Vanagonner wrote:
I agree Chris, the SS tubes will increase the cathodic area, resulting in a higher current density in the aluminum (anode).
Here's a paragraph for anyone wants to skool up-
(college chemistry)
Factors Affecting Galvanic Corrosion
1. Area Effect.
When current flows between the anode and cathode, the CURRENT will be the same in the anode and cathode independent of the surface area of each electrode. It is the CURRENT rather than the CURRENT DENSITY which is equal for the anodic and cathodic reactions. Therefore, if the current flowing between the anode and the cathode is one amp and the surface areas are one cm2, then the current density in each electrode is one A/cm2. However, if the area of the anode is only 0.1 cm2, then the current density in the anode with the same one amp flowing is 10 A/cm2. From Faradays Law, the corrosion rate depends on the CURRENT DENSITY in the anode. In this case decreasing the surface area of the anode increases the corrosion rate by a factor of 10.
As a general rule to minimize galvanic corrosion, the anode area should be large and the cathode area should be small. This leads to a result that on first appearance would seem incorrect. For protection from galvanic corrosion, the CATHODE of the system should be painted if a coating is applied. This arises from the area effect, in that if the paint is damaged by a scratch for example, then a small cathode to large anode area ratio is formed which results in minimizing corrosion rates. If the anode is painted, then damage to the paint results in a large cathode to small anode ratio which results in large corrosion rates in the anode and rapid penetration into the metal.
The anode to cathode area effect is an important characteristic. It is important in several other forms of corrosion including pitting corrosion, crevice corrosion, stress corrosion cracking and corrosion fatigue. Remember the important effects of the anode to cathode area ratios.


It seems the case against uncoated stainless steel pipes is pretty damning (can I use that word on the internet? ) . The solution would appear to be coated stainless steal, if you must have stainless for its durability, or plain steel, or plastic or rubber.
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Last edited by 240Gordy on Mon Jan 25, 2010 11:47 am; edited 1 time in total
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climberjohn
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PostPosted: Mon Jan 25, 2010 9:55 am    Post subject: Reply with quote

Calling tencent . . .

As one of the Samba resident engine and electrical experts, what do you think about this?
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PDXWesty
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PostPosted: Mon Jan 25, 2010 9:56 am    Post subject: Reply with quote

Seems to me like you're just trying to start another argument. Galvanic corrosion is prevented in piping systems of dissimilar metals by providing dielectric fittings (non conductive) between the dissimilar metals. It seems the number of rubber hoses and couplings in the system more than makes up for this. You're making a big deal out of nothing.
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Wildthings
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PostPosted: Mon Jan 25, 2010 10:18 am    Post subject: Reply with quote

PDXWesty wrote:
Seems to me like you're just trying to start another argument. Galvanic corrosion is prevented in piping systems of dissimilar metals by providing dielectric fittings (non conductive) between the dissimilar metals. It seems the number of rubber hoses and couplings in the system more than makes up for this. You're making a big deal out of nothing.


I agree somewhat, but not fully. If a metal pipe touches a ground anywhere then the electrical circuit will have been completed.

It would be nice if someone where to do a test by taking a chunk from an old head and a 304 SS plate and putting them in a hot bath with some two year old antifreeze for a thousand hours or so.
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PostPosted: Mon Jan 25, 2010 11:32 am    Post subject: I "worked" in a cathodic engineering environment Reply with quote

...for one summer eons ago. We would go around telling people that their natural gas lines (and others) were corroding and likely to kill us all (we also protected sunken fuel storage (gas stations) etc.)). The commercial peeps always bought in, so we would dig a bunch of holes and sink is these 20lb bags of magnesium and tie them up to the system. We also had some means of measuring whether or not we had the system isolated so the magnesium would indeed be the sacrificial anode (?) rather than some other unsuspecting piece of metal in the system.

That is just a little example that might allow for other to better understand this issue. You can also just take about 10 seconds to see how rust works, and another minute to learn how cathodic engineering is meant to divert the cancer. It seems to me that years ago, car companies tried using sacrificial anodes (magnesium I am guessing) on cars (bodies), but the lack of current prevented success in prohibiting rust. Or maybe that was all a dream?

Anyway, it seems like the success of the anode is easy to measure, with the quickness? I mean, we did it, and we were just a bunch of inebriated college kidz.

So, do I need to replace the SS lines or just buy a different engine, put in some non-conductive fittings...I think all in all this ranks like #473 on my vanagon to-do list. But interesting none the less. Peace
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PostPosted: Mon Jan 25, 2010 11:38 am    Post subject: Reply with quote

I think this is one of three current posts about coolant pipe metallurgy. I think it's a total non-issue. The plastic pipes are going to last long after the humans and cockroaches are extinct. The only problem with the plastic pipes is the loosening inserts, which can be permanently held in place with the gowesty kit that costs $50. Problem solved. No coolant loss, permanent pipes, no rust.
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240Gordy
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PostPosted: Mon Jan 25, 2010 11:49 am    Post subject: Reply with quote

PDXWesty wrote:
Seems to me like you're just trying to start another argument. . . .


absolutely not. I am trying to get to the bottom to this. I am at work and don't have time to finish my OP but I am not trying to start a war just . . .
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PostPosted: Mon Jan 25, 2010 11:56 am    Post subject: Reply with quote

If the stainless steel coolant pipe is insulated from the chassis, there is no circuit that allows the current to flow so no corrosion can take place from the inside. The original steel pipes are mounted using plastic clamps and all the ends are connected to the engine and radiator using rubber hoses. I thought the steel coolant pipes that rust were rusted from the outside in and not from inside out, assuming the anti-freeze are in good health.
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?Waldo?
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PostPosted: Mon Jan 25, 2010 12:32 pm    Post subject: Reply with quote

What about those times when the underside of the van is wet or better yet, wet with water from a salted road. Wouldn't the water on the rubber hoses or isolators complete the circuit?
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PostPosted: Mon Jan 25, 2010 12:37 pm    Post subject: Reply with quote

Hope my freshly painted hub caps don't go 'galvanic', is that contagious?
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PostPosted: Mon Jan 25, 2010 12:47 pm    Post subject: Reply with quote

funagon wrote:
I think this is one of three current posts about coolant pipe metallurgy. I think it's a total non-issue. The plastic pipes are going to last long after the humans and cockroaches are extinct. The only problem with the plastic pipes is the loosening inserts, which can be permanently held in place with the gowesty kit that costs $50. Problem solved. No coolant loss, permanent pipes, no rust.


I'm convinced that the GoWesty insert kit is complete bunk. I started a thread here:

http://www.thesamba.com/vw/forum/viewtopic.php?p=4345097#4345097

If anyone wants to reply to that, then the appropriate place to do so would be in the linked thread.
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PostPosted: Mon Jan 25, 2010 12:51 pm    Post subject: Reply with quote

Why is this a new thread? This would fit just as well under either of the two previous entries, particularly under Loogy's previous post.

Isn't the samba scattered enough already?
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PostPosted: Mon Jan 25, 2010 12:58 pm    Post subject: Reply with quote

noganav wrote:
Why is this a new thread? This would fit just as well under either of the two previous entries, particularly under Loogy's previous post.

Isn't the samba scattered enough already?


Are you talking about this thread that we are currently in or the thread I just started about the GoWesty coolant pipe repair kit? If you are talking about the GW repair kit thread, then I started it as a separate thread because it is a different topic and I have been criticized before for continuing a discussion that was off the topic of the original post in a thread.
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PostPosted: Mon Jan 25, 2010 1:28 pm    Post subject: Reply with quote

I dont get it. Are the pipes grounded that good against the frame(with all the talk of Vgons needing clean grounds....)?
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PostPosted: Mon Jan 25, 2010 1:28 pm    Post subject: Reply with quote

IMHO, the GW repair kit is an entirely new topic, so "new thread" away!!

This thread, as started, seems like a spin off of the other coolant pipe debate that has, unfortunately, spun down the death spiral of any thread that dares challenge TK.

Not sure why we needed this one, but I'm not the thread police.
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PostPosted: Mon Jan 25, 2010 3:20 pm    Post subject: Reply with quote

I was talking about this thread, but I'm not the thread police either. It just seems like it's already hard enough to find information on here without spawning new threads on topics that are already alive in other currently active threads.

Anyway, this OT and thus contributing to the problem. My apologies.
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PostPosted: Mon Jan 25, 2010 6:26 pm    Post subject: Reply with quote

Coolant, being made with water is conductive. It doesn't matter how many rubber parts you have separating your metals. The electrolyte is the conductor.
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PostPosted: Mon Jan 25, 2010 6:40 pm    Post subject: Reply with quote

Vanagonner wrote:
Coolant, being made with water is conductive. It doesn't matter how many rubber parts you have separating your metals. The electrolyte is the conductor.


I hate to disagree with you, but it's basic engineering practice (based on real science) to seperate the metals and it does work. If you have a sufficient length of rubber or plastic seperating the pipes, the galvanic process is stopped.

"Preventing Galvanic Corrosion: One way is to electrically insulate the two metals from each other. Unless they are in electrical contact, there can be no galvanic couple set up. This can be done using plastic or another insulator to separate steel water pipes from copper-based fittings or by using a coat of grease to separate aluminium and steel parts. Use of absorbent washers that may retain fluid is often counter-productive. Piping can be isolated with a spool of pipe made of plastic materials or made of metal material internally coated or lined. It is important that the spool has a minimum length of approx 500 mm to be effective."
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PostPosted: Mon Jan 25, 2010 6:41 pm    Post subject: Reply with quote

Vanagonner wrote:
Coolant, being made with water is conductive. It doesn't matter how many rubber parts you have separating your metals. The electrolyte is the conductor.


It takes two conductors to make a circuit. The coolant is only one. Plus with the correct additives coolant is not much of a conductor, this is why you either must change the coolant after a certain amount of use or replenish the additive package.

This may not be the most definitive page about antifreeze, but people should be aware of what they speak.

http://74.125.155.132/search?q=cache:35mk9xhuTGwJ:...&gl=us
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PostPosted: Mon Jan 25, 2010 7:23 pm    Post subject: Reply with quote

I started this thread to consolidate the info about stainless steel as causing galvanic corrosion of the aluminum in the cylinder heads, rather than the threads which talk about the "quality and durability" of the pipes themselves, in the other threads. It was clear that readers were not getting the point that the corrosion issue is not about the durability of the pipes, but rather the effect they have on aluminum parts in contact with coolant in the cooling system.

To respond to some posts about the quality of coolant itself and how it effects corrosion, keep in mind that the coolant MUST be conductive for the coolant level sensor too work. A weak charge must go through the coolant from prong to prong, or your warning like will light up.

Mitigating the effect with sacrificial anodes: why add more complexity and wear parts to something that can be avoided in the first place, by

1. Using a non-conductive coating on metallic cooling system parts,

or,

2. Using non-metallic parts only in the cooling system.
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