Galmac^®: The New Generation

Maccaferri Mission

Maccaferri Gabions has always researched and developed technically advanced and improved solutions to meet the requests of its customers worldwide dealing with soil erosion environmental protection related problems.

The Problem

The increasing environmental decay, due mostly to more corrosive agents in the atmosphere and in watercourses has led Maccaferri to look into products which have a better corrosion resistance than traditional zinc coating. Recent findings corroborated by several independent field trials have provided a new solution which lengthens the life of steel wire products and dramatically reduces the costs of maintenance. Proven in both laboratory and field tests, a zinc-aluminum alloy has been chosen by Maccaferri from many other possible solutions and prototypes.

GalMac^®

In 1979 ILZRO (International Lead-Zinc Research Organization) was awarded a research contract to conduct specific tests on the eutectic Zn-(/5%)-Al alloy which as been proved to have a lifespan greater than traditional steel coatings. This new zinc-based coating has been named Galfan® which stands for "Galvanization Fantastique". Since then millions of dollars have been invested in research in universities, industry and specialist research centers to improve the new coating which is today acknowledged to be a breakthrough in galvanizing technology both for its chemical-physical characteristics and for its quality.

Since 1995 Maccaferri Gabions has been manufacturing new products using a Galfan® coated wire named GalMac® (Galfan Maccaferri.)

Increased Corrosion Resistance of GalMac^®

• GalMac® has a fine non-porous eutectic microstructure which corrodes more uniformly than the laminar random disposition of traditional galvanizing, thus slowing its rate of corrosion.
• GalMac® combines the strengths of both zinc and aluminum, giving better passive barrier protection than regular galvanizing and better sacrificial protection than alloys having a lower zinc composition. In fact, aluminum is more electropositive than zinc, and is therefore characterized by lower corrosion rates, whereas zinc has a cathodic feature which promotes its sacrificial protection: when zinc is scratched, damaged or abraded away, oxides cover the exposed steel surface.
• Oxidation involves a chemical reaction between steel, oxygen and water causing the formation of both a crystalline porous mass and uniform aluminum crystals which make GalMac's® passivating performance more effective.
• Aging tests have demonstrated that the percentage of aluminum on the external surface of GalMac® products increases with time thus improving the GalMac® corrosion resistance over the life of the structure.
• GalMac® is also a highly ductile alloy which has been found to have an improved formability withstanding flaking and cracking when it is bent or twisted.

Exposure to Corrosive Environments

The improved resistance to corrosion and the consequent increase in durability have been proven qualitatively by independent tests in a wide range of corrosive environments.

The results gathered from different exposure have proved that GalMac® products have an improved corrosion resistance.

Durability

The exposure test results have substantiated our assumptions that Galfan's corrosion resistance progressively improves over time.

GalMac® corrosion rate per year is very rapid, at first, then it slows down progressively until it virtually stabilizes. This phenomenon occurs when the surface coating produces an oxidizing film which covers the exposed steel wire blocking both the wire oxidation and corrosion. Oxidation of buried steel wires tends to disappear completely.

GalMac^® Plastic Coated Wire

Maccaferri has been promoting its plastic coated products to provide a long-lasting solution suitable for all applications where an improved corrosion resistance is required. This type of coating completely protects the wire from corrosion.

Specifications

Presently new international standards covering the Zn-5%Al steel wire are being drafted, however they will differ from the current standards only in regard to the chemical composition of the original materials.

The thickness of GalMac® coated wire complies with BS 443, NF A 91-131, DIN 1548, UNI 8018, ANBT NBR 8964.

Standard specifications adopted are:

• EN /Euronorm 10244/2 Zinc or Alloy coatings on steel wire - draft
• ASTM 856 Zinc-5% Alluminum-Mishmetal Alloy Coated Carbon Steel

Characteristics of GalMac^® Wire

• Resistance 372 � 490N/mm²
• Elongation >= 12%
• Coating
  2.0 mm >= 240 g/m²
  2.2 mm >= 240 g/m²
  2.4 mm >= 260 g/m²
  2.7 mm >= 260 g/m²
  3.0 mm >= 275 g/m²
  3.4 mm >= 275 g/m²
  3.9 mm >= 290 g/m²