Repair of corroded reinforcement in concrete using sacrificial anodes
AssigneeAston Material Services Limited
InventorChristopher L Page
Life of this patent
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Abstract
Reinforcement in concrete is cathodically protected by galvanically connecting a sacrificial anode, such as a zinc or zinc alloy anode, to the reinforcement, and contacting the anode with an electrolyte solution having a pH which is maintained sufficiently high for corrosion of the anode to occur, and for passive film formation on the anode to be avoided. The pH of the electrolyte is preferably at least 0.2 units, and preferably from 0.5 units to more than 1.0 units, above the pH value at which passivity of the anode would occur. The electrolyte may be for example sodium hydroxide or potassium hydroxide but is preferably lithium hydroxide which also acts as an alkali-silica reaction inhibitor.
Claims16
A method of cathodically protecting steel reinforcement in concrete, comprising the steps of:
- (a) galvanically connecting a sacrificial anode to the steel reinforcement, the anode being zinc or a zinc alloy so as to have a more negative electrode potential than that of the steel reinforcement;
- and
- (b) casting around the anode a porous material containing an electrolyte solution with sufficient alkali that its pH is at least about 14 so as to be above a pH at which passivity of the anode would occur, whereby corrosion of the anode and substantial protection of the steel reinforcement are maintained and passive film formation on the anode is avoided.
A unit for use in the cathodic protection of steel reinforcement in concrete, the unit comprising:
- a sacrificial anode for embedding in the concrete and for connecting to the reinforcement, the anode being zinc or a zinc alloy so as to have a more negative electrode potential than that of the steel reinforcement;
- and
- a repair material for repairing concrete cast around the anode such that the anode is substantially enclosed in the repair material, the repair material containing an electrolyte having a pH which is at least about 14 so as to be above a pH at which passive film formation on the anode would occur when the anode is galvanically connected to the steel reinforcement, whereby corrosion of the anode and substantial protection of the steel reinforcement are maintained and passive film formation on the anode is avoided.
A repair kit for corrosion-induced cracked steel reinforced concrete, the repair kit comprising:
- a container;
- a sacrificial anode for embedding in the concrete and for connecting to the metal reinforcement, the anode being zinc or a zinc alloy so as to have a more negative electrode potential than that of the steel reinforcement;
- and
- a repair material for concrete for contacting the anode and containing an electrolyte having a pH which is at least about 14, and thereby above the pH value at which passivity of the anode would occurs when the anode is galvanically connected to the steel reinforcement, and whereby corrosion of the anode and substantial protection of the steel reinforcement is maintained, and passive film formation on the anode is avoided;
- and
- wherein said sacrificial anode and said repair material are disposed in the container.
Dependencies are inferred from the claim text.