Determination of chloride corrosion threshold for metals embedded in cementitious material
AssigneesMMFX Steel Corporation of America, The Texas A&M University System
InventorsDavid Trejo, David R. Miller
Life of this patent
Estimating the term…
Abstract
The chloride corrosion threshold of a metal embedded in a cementitious structure is determined in an accelerated manner by using an electric field to increase the rate of migration of chloride ion into the structure and monitoring the interface between the metal and the cementitious material to detect the onset of corrosion, then determining the chloride corrosion threshold, which is defined as the chloride content of the cementitious material once corrosion has begun. This determination can be performed over a time period of as little as 2 to 3 weeks rather than the months or years required by conventional chloride corrosion test procedures.
Claims26
A method for determining the chloride corrosion threshold of metal embedded in a cementitious material, said method comprising:
- (a) encasing a sample of said metal in a set mass of said cementitious material in which are embedded components comprising an anode, a counter electrode and electrical leads capable of individually joining said metallic sample, said anode and said counter electrode to electrical circuitry external to said mass,
- (b) placing a liquid solution of chloride ions in contact with said set cementitious material, with a cathode immersed in said liquid solution;
- (c) applying in time increments an electric potential between said cathode and said anode to induce migration of chloride ions from said liquid solution through said set cementitious material to said metallic sample, without directly polarizing said sample;
- (d) between time increments of step (c), determining the half-cell potential of said metallic sample or applying an electric potential between said metallic sample and said counter electrode while detecting the value of a parameter indicative of the presence or absence of corrosion activity of said metal at an interface between said metallic sample and said set cementitious material;
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- (e) analyzing said set cementitious material for chloride content at a location adjacent to said metallic sample at a time corresponding to the point at which the half-cell potential or corrosion activity indicated by said detected value exceeds a selected critical level, said chloride content thus detected representing said critical chloride threshold.
Apparatus for the determination of the chloride corrosion threshold of a metal embedded in cementitious material, said apparatus comprising:
- a mold having an open top to receive cementitious material and a sample of said metal and to allow said cementitious material to set into a solid unitary block with said metallic sample embedded therein;
- a receptacle capable of retaining liquid and shaped to be placed in communication with said open top of said mold in such a manner that when liquid is retained in said receptacle and a solid unitary block resides in said mold, said liquid contacts said solid unitary block;
- means for applying an electric potential between the interior of said mold and the interior of said receptacle;
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- means for determining current density at the surface of a metallic sample in said mold when an electric potential is applied across said surface.
Dependencies are inferred from the claim text.