Protective Systems for Corroded Steel
| Protective System | System description | Comments | |
| Benefits | Concrete | ||
| Epoxy Bar Coating
|
Two components epoxy coating field applied over cleaned reinforcing steel surface.
Epoxy is brushed onto the bar. |
Provides impermeable dielectric barrier, isolates the steel from contact with oxygen, moisture and chlorides. | 1.Very difficult to achieve 100% coverage. Intersections and backsides of rebar create an almost impossible access.
2. Lower bond with repair material. 3. Isolates the steel from high pH material 4. Contaminates adjacent concrete surfaces with epoxy.
|
| Cement based Coating
|
Alkaline cement-based polymer-modified bar coating.
Applied to the bar with a brush. |
1. Maintains the high alkalinity environment surrounding the bar.
2. Does not decrease the repair material bond to bar. |
The coatings are susceptible to deterioration due to the continued chloride ingress. |
| Sacrificial Metallic Coating
|
Sacrificial metallic coating (galvanic anode method of cathodic protection ) is usually a zinc rich primer. | This coating improves the corrosion resistance of the coated steel in the repair area.
Corrosion products of the sacrificial material are not as expensive and detrimental to repair material as mild steel corrosion products. |
1. Their effectiveness in preventing corrosion of the unexposed steel in chloride contaminated existing concrete adjacent to the repair is not yet known.
2. Zinc rich primer protection has a high consumption (corrosion) rate. |
| Corrosion Inhibitor in Repair Material
|
Calcium nitrite inhibitor added to repair material mix. | 1. Delays the corrosion of embedded steel.
2. Very easy to use. |
Calcium nitrite is effective in maintaining passivity only if present in sufficiently high concentration around the rebars.
The admixture tends to be dispersed in the repair and adjacent portions of the existing concrete rather than at repair/ steel interface. |
