.... I wonder how many inspectors spotted this!

quote:

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Copper brake tube was clipped with the original Cortina bent metal bits on the rear axel - this would fail due to dissimilar metals corroding the copper tube; glad he spotted this ( original Ford brake tube is steel, so no probs);

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What a load of tosh!

It just shows that a little knowledge is a dangerous thing. When galvanic corrosion occurs between dissimilar metals it is the most reactive (anodic) metal which corrodes.

Steel is more anodic that copper so it is the steel which will corrode.

He obviously didn't listen in his science lessons.

The list below illustrates my point.

Table 1. Standard Galvanic Series Of Common Metals In Sea Water
(Ranked from most corrodible to least corrodible)

Anodic End (most corrodible)

Magnesium
Magnesium Alloys
Zinc
Galvanized Steel
Aluminum 5052H
Aluminum 3004
Aluminum 3003
Aluminum 1100
Aluminum 6053
Alcad Aluminum Alloys
Cadmium
Aluminum 2017
Aluminum 2024
Low-carbon Steel
Wrought Iron
Cast Iron
Ni-Resist
Type 410 Stainless Steel (active)
50Sn-50Pb Solder
Type 304 Stainless Steel (active)
Type 316 Stainless Steel (active)
Lead
Tin
Muntz Metal (C28000)
Manganese Bronze (C67500)
Naval Brass (C46400)
Nickel (active)
Inconel (active)
Cartridge Brass (C26000)
Admiralty Metal (C44300)
Aluminum Bronze (C61400)
Red Brass (C23000)
Copper (C11000)
Silicon Bronze (C65100)
Copper Nickel, 30% (C71500)
Nickel (passive)
Inconel (passive)
Monel
Type 304 Stainless Steel (passive)
Type 316 Stainless Steel (passive)
Brazing Filler Metals (silver-copper-zinc alloys)
Silver
Gold
Platinum

Cathodic End (least corrodible)

True- worst case scenario would be the clip corroding resulting in a lose pipe.

Being Ford the clip would have rusted away long before galvanic corrosion occured

Wrong. You're all wrong! The SVA man's never wrong and always right, that's his job you know (Stands back!)
No I gree really, was just looking for a periodic table to prove it but Kendo's well in there.

What the heck, it should have a rubber sleeve, or insulated type P clip holding the brake pipe on. The galvanic corrosion will take much longer to puncture the pipe than a steel clip rubbing directly onto the copper pipe. (even if it is done up tightly, it will still vibrate)

Thats a much better reason for the fail.


(ducks and runs for cover)

mine failed on exactly that at sva! just put some split rubber tube around the pipes and that made them happy

Yes MOT failure point -- Rubber sleeve required to prevent chaffing even on a steel bundy pipe. Chaffing causes fretting corrosion.

Copper brake pipes ---- not great idea anyway -- Kunifer is the stuff to use.

hi again
from memory"i am a relic" ford used to fit a small rubber sleave on the bundy tube where required.
graham.

quote:

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Originally posted by BenB

Being Ford the clip would have rusted away long before galvanic corrosion occured

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When galvanic corrosion occurs between dissimilar metals it is the most reactive (anodic) metal which corrodes.

Steel is more anodic that copper so it is the steel which will corrode.

Are you sure?

I've seen it where copper hot water pipes have been rested on bare angel iron supports and its pin-holed the pipe.. it did take a long time tho, probably over 40 years.

Unless it was the movement of the pipe or thermal expansion and contraction making it rub on the bracket, but aparently its not un-common for them to do this and all new steel brackets have rubber pads in them.