A possible cause of structural decay is ‘concrete cancer’. This is caused when water and contaminants seep into concrete and react with the steel reinforcement. The steel reinforcement corrodes and the concrete structure is weakened. To prevent this from happening cathodic protection can be employed.
Cathodic protection uses an anode to apply a current to the reinforcement. The steel reinforcement then becomes cathodic and as such resistant to corrosion. This cathodic resistance against corrosion decreases the chances of concrete cancer and potentially increases the structural life of your building or structure.
Galvashield
Type 1A Embedded Galvanic Anode Units with 2G Technology
The Galvashield XP range of embedded galvanic anode units utilize an innovative zinc anode core design surrounded by an enhanced formulated cement-based mortar to provide corrosion mitigation to reinforced concrete structures. The anode units are alkali-activated (Type 1A) with an internal pH of 14 or greater to keep the zinc active over the life of the anode while being non-corrosive to reinforcing steel. The anode units utilize 2G Technology™ to provide higher current output. Once installed, the zinc anode corrodes preferentially to the adjacent reinforcing steel, thereby providing galvanic corrosion prevention or corrosion control.
Applications
- Mitigates incipient anode formation (halo effect) in patch repair
- Bridge widening and other structure modifications
- Slab replacements, expansion joint repairs and other interfaces between new and existing concrete
- Repair of prestressed and post-tensioned concrete
- Chloride contaminated or carbonated concrete
- Repair of structures with epoxy-coated rebarMitigates incipient anode formation (halo effect) in patch repair
- Bridge widening and other structure modifications
- Slab replacements, expansion joint repairs and other interfaces between new and existing concrete
- Repair of prestressed and post-tensioned concrete
- Chloride contaminated or carbonated concrete
- Repair of structures with epoxy-coated rebar
Features and Benefits
- Proven technology – Galvashield anodes have an extensive 10+ year track record in the field and have received British Board of Agrément (BBA) approval.
- Type 1A anode – alkali-activated to maintain activity of zinc while being non-corrosive to reinforcing steel.
- 2G Technology™ – provides enhanced current output and protection.
- Cast zinc core – provides high anode utilization in addition to a secure long-term connection between the zinc and the lead wires .
- Integral steel lead wires – allows for quick and convenient anode installation. Provides dependable steel-to-steel contact with no intermediate materials such as galvanizing (which can corrode over time) that may compromise the long-term electrical connection.
- BarFit™ design – grooved edges on Galvashield XP2 and XP4 anode units assist with secure anode placement.
- Economical – provides localized protection where it is needed the most, at the interface of the repair and the remaining contaminated concrete.
- Versatile – can be used for both conventionally reinforced and prestressed or post-tensioned concrete.
- Low maintenance – requires no external power source or system monitoring.
- Long lasting – 10 to 20 year service life* reduces the need for future repairs.
- Proven technology – Galvashield anodes have an extensive 10+ year track record in the field and have received British Board of Agrément (BBA) approval.
- Type 1A anode – alkali-activated to maintain activity of zinc while being non-corrosive to reinforcing steel.
- 2G Technology™ – provides enhanced current output and protection.
- Cast zinc core – provides high anode utilization in addition to a secure long-term connection between the zinc and the lead wires .
- Integral steel lead wires – allows for quick and convenient anode installation. Provides dependable steel-to-steel contact with no intermediate materials such as galvanizing (which can corrode over time) that may compromise the long-term electrical connection.
- BarFit™ design – grooved edges on Galvashield XP2 and XP4 anode units assist with secure anode placement.
- Economical – provides localized protection where it is needed the most, at the interface of the repair and the remaining contaminated concrete.
- Versatile – can be used for both conventionally reinforced and prestressed or post-tensioned concrete.
- Low maintenance – requires no external power source or system monitoring.
- Long lasting – 10 to 20 year service life* reduces the need for future repairs.
*As with all galvanic protection systems, service life and performance is dependent upon a number of factors including reinforcing steel density, concrete conductivity, chloride concentration, humidity and anode spacing.
Cut-away of Galvashield XP4
| Level of Protection | Description | Galvashield XP/XPT | Galvashield XP2/XP$ |
| Corrosion Prevention | Mitigates initiation of new corrosion activity | – | – |
| Corrosion Control | Reduces on-going corrosion activity | – | |
| Cathodic Protection | Reduce or eliminate on-going corrosion activity |
“Ring Anode” Corrosion (without Galvashield XP)
Galvashield XP prevents “Ring Anode” Corrosion
Specification Clause
Embedded galvanic anodes shall be pre-manufactured with nominal [add zinc mass] of zinc in compliance with ASTM B418 Type II cast around a pair of uncoated, non-galvanized steel tie wires and encased in a highly alkaline cementitious shell with a pH of 14 or greater. The anode unit shall contain no added sulfate nor shall it contain chloride, bromide or other constituents that are corrosive to reinforcing steel. Anode units shall be supplied with integral unspliced wires with loop ties for tying to the reinforcing steel.
How It Works
When two dissimilar metals are coupled together in an electrolyte (in this case concrete), the metal with the higher potential for corrosion (zinc) will corrode in preference to the more noble metal (reinforcing steel). Galvashield XP-type anodes are embedded in concrete repairs to provide corrosion prevention or corrosion control to the reinforcing steel in the adjacent area.
Product Anode Details
| Anode Name | Anode Type | Nomimal Dimension (mm) | Zinc Mass (g) |
| XPT | 1A-P | 125 mm x 25 mm x 25 mm | 60 |
| XP | 1A-P | 65 mm (dia.) x 30 mm | 60 |
| XP2 | 1A-C | 70 mm x 65 mm x 30 mm | 100 |
| XP4 | 1A-C | 110 mm x 55 mm x 30 mm | 160 |
Anode Type and Class
1 – Embedded in Repairs
2 – Embedded in Sound Concrete
A – Alkali-activated using High pH
H – Halide-activated using Corrosive Salts
P – Corrosion Prevention
C – Corrosion Control
Installation Instructions
Concrete shall be removed from around and behind all corroding rebar in accordance with good concrete repair practice such as ICRI Guideline R310.1R. Exposed reinforcing steel should be cleaned to remove all residual rust and concrete residue.
The anode units and repair material should be installed immediately following preparation and cleaning of the steel reinforcement. The location and spacing of the units shall be as specified by the designer (refer to design criteria). The units can be placed around the perimeter of the repair or on a grid pattern to protect a second mat of steel if required.
Securely fasten the anode units from the side or beneath the exposed rebar as close as practical to the surrounding concrete (preferably within 4 in. (100 mm)) while ensuring that enough space remains to fully encapsulate the unit in the repair. Wrap the tie wires around the clean reinforcing steel at least one full turn in opposite directions and twist tight for secure connection. The minimum cover of the repair material over the units should be ¾ in. (20 mm).
Anode-to-steel continuity and steel-to-steel continuity within the patch should be verified with an appropriate meter; discontinuous steel should be tied to continuous bars using steel tie wire and re-tested. A value between 0 and 1 ohm should be achieved.
Repair Materials
For optimum performance, use a repair material with resistivity less than 15,000 ohm-cm. If a higher resistivity repair material is to be used or if the resistivity of the material is unknown, pack Galvashield Embedding Mortar between the anode unit and the substrate to provide an ionically conductive path to the substrate. Prior to placing the repair material, pre-wet the concrete substrate and the anode units to achieve a saturated surface dry condition, then complete the repair. Do not soak the anode units for greater than 20 minutes.
Precautions
Galvashield XP-type anode units are intended to provide localized corrosion prevention or corrosion control and do not address or repair structural or concrete damage. Where structural damage exists, consult a structural engineer. To provide protection to a broader area, install Galvashield CC anode units on a grid pattern or consult us for further product recommendations.
Storage
Store in dry conditions in the original unopened box. Avoid extremes of temperature and humidity. Units should be installed within 2 years.
Health and Safety
As with all cement-based materials, contact with moisture can release alkalis which may be harmful to exposed skin. Galvashield anode units and Galvashield Embedding Mortar should be handled with suitable gloves and other personal protective equipment in accordance with standard procedures for handling cementitious materials. Additional safety information is included in the Material Safety Data Sheet.
