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[TowerTalk] aluminum wire corrosion...

Subject: [TowerTalk] aluminum wire corrosion...
From: Jim Lux <>
Date: Fri, 14 Jul 2006 07:04:40 -0700
List-post: <>
A bit of googling turns up some info that indicates that it should be 
possible to get decent longevity for buried aluminum radial fields:
Al-alloys in Soil : Corrosion Hazards

which has this:

Corrosion of the copper-containing 2XXX and 7XXX series alloys in moist 
low-resistivity soils, measured by weight loss and pitting depth, is 
several times greater than corrosion of the more resistant 1XXX, 3XXX, 
5XXX, and 6XXX series alloys. Use of cathodic protection or Alclad products 
effectively reduces corrosion or limits penetration.

In actual service, alloys 3003, 6061, and 6063 (which are most frequently 
used for pipelines) showed corrosion attack ranging from almost none to 
deep pitting after many years of service in unprotected conditions. 
Cathodically protected sections of some of the same pipes in corrosive soil 
showed no attack or only mild etching.

--- This seems to say that picking the right alloy AND some cathodic 
protection might be a good way to do it.  Note that one can create the 
protection current either with a sacrificial electrode (so the current is 
produced by galvanic action) OR by externally applying a suitable current 
to an inert electrode.  Seems to me that the latter scheme, with a solar 
panel, might be the way to go, depending on the current required.

And also this:


Abstract:A description is provided of laboratory and field evaluation 
procedures used to evaluate the corrosion resistance of aluminum culverts, 
storm drains, structural plates, and retaining walls. Relationships of the 
physical and chemical properties of waters and soils with the performance 
of aluminum pipe are discussed. Results indicate that there is a 
qualitative relationship between corrosion resistance of aluminum and the 
water and soil pH and resistivities, with good performance of unprotected 
aluminum pipe observed in the pH range of 4 to 9 and minimum resistivities 
greater than 500 ohm-cm. The extent of localized corrosion on the soil side 
of pipe can be accurately measured by portable ultrasonic metal thickness 
instruments. The low pitting corrosion rates of the thin wall Alclad 3004 
culvert are demonstrated to be the results of the galvanic protection 
provided by the cladding alloy.
Supplemental Notes: This paper appeared in Transportation Research Record 
N1001, Symposium on Durability of Culverts and Storm Drains.
Pagination: p. 77-87
<>Summerson, T J
Features: Figures (12); References (15); Tables (4)

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