Electrochemical ZRA test cells for determination of galvanic corrosion rates in atmospheric environments
Inventors
Hangarter, Carlos M. • Policastro, Steven A.
Assignees
Publication Number
US-11029244-B1
Publication Date
2021-06-08
Expiration Date
2038-10-26
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Abstract
The invention is directed to a real-time, zero resistance ammeter (ZRA) galvanic corrosion detection instrument that is adapted to measure corrosion under atmospheric conditions. The instrument may be used in accordance with methods for selecting materials based on environmental conditions and electrolyte chemistries. The electrochemical ZRA test cell of the invention may further be used to determine galvanic corrosion susceptibility, aid in forecasting corrosion, and determine the extent of corrosion based on environmental factors.
Core Innovation
The invention provides a real-time, zero resistance ammeter (ZRA) galvanic corrosion detection instrument adapted to measure corrosion under atmospheric conditions. It includes configurations of anodes and cathodes with electrolytes provided as droplets or thin films, separated by a salt bridge that electrolytically connects the electrolytes at the anode and cathode. This arrangement allows galvanic corrosion kinetics to be measured in isolated electrolytes, removing convolution arising from reaction product interactions common in other methods.
The invention further provides methods for measuring corrosion, wherein corrosion current densities are measured using a zero resistance ammeter connected to anodes and cathodes with either separated electrolytes connected via a salt bridge or a single electrolyte contacting both electrodes. These measurements enable comparison of corrosion rates to polarization scan intersection points, allowing determination of accelerated corrosion due to the presence of the electrolytes or accumulation of corrosion reaction products.
The problem being solved is that atmospheric corrosion involves thin film and discontinuous electrolytes with different behaviors than bulk electrolytes, including limited ionic species availability and accumulation of corrosion products affecting kinetics. Existing methods intertwine kinetics with reaction product interactions, producing convoluted results. There is a need for accurate electrochemical corrosion measurements under atmospheric conditions to better understand material interactions and forecast corrosion for time-of-service predictions.
Claims Coverage
The patent includes four independent claims covering instruments and methods for measuring galvanic atmospheric corrosion, focusing on configurations of electrodes, electrolytes, salt bridges, and zero resistance ammeters, and methods for corrosion current density measurements.
Zero resistance ammeter galvanic atmospheric corrosion instrument with separated electrolytes and salt bridge
An instrument comprising an anode and cathode each provided with electrolytes as droplets or thin films, electrically connected by a ZRA, and electrolytically connected with a salt bridge that separates the anode and cathode electrolytes to allow measurement of galvanic corrosion kinetics.
Method for measuring galvanic atmospheric corrosion current density using separated electrolytes
A method involving providing anode and cathode with separated electrolytes connected by a salt bridge, electrically connecting a zero resistance ammeter to the electrodes, measuring galvanic corrosion current density, and comparing it to polarization scan intersection points to determine corrosion acceleration due to electrolytes.
Method for measuring galvanic atmospheric corrosion with single electrolyte contact
A method providing anode and cathode in contact with a single electrolyte, electrically connecting a zero resistance ammeter, measuring corrosion current density, and comparing it to current density from separated electrolytes galvanic couple to assess corrosion acceleration caused by corrosion reaction product accumulation.
Zero resistance ammeter galvanic atmospheric corrosion instrument with partial surface electrolyte exposure
An instrument similar to the first, but wherein less than the entire surface of the anode or cathode is exposed to the electrolyte, with a salt bridge electrolytically connecting the separated electrolytes and a ZRA electrically connecting the electrodes.
In summary, the claims define instruments and methods enabling measurement of galvanic atmospheric corrosion rates by separating electrolytes with a salt bridge and using zero resistance ammeters, facilitating corrosion assessment with and without reaction product effects, and controlling electrolyte exposure on electrode surfaces.
Stated Advantages
Ability to measure galvanic corrosion rates independently of reaction product interactions that can drastically alter reaction rates.
Enables rapid survey and scanning of environmental conditions and materials under varied atmospheric conditions such as diurnal cycles, humidity, temperature, and pollutants.
Permits better informed material selection during design phases and more accurate time-of-service predictions for condition-based maintenance schedules.
Allows observation of transient electrochemical behavior more significant to atmospheric corrosion compared to marine environments.
Facilitates steady-state and transient corrosion measurements in small electrolyte volumes such as droplets and thin films.
Documented Applications
Measuring galvanic corrosion current density of metal and alloy couples under atmospheric conditions using separated electrolytes connected by a salt bridge.
Using a ZRA galvanic atmospheric corrosion kinetics detection instrument to determine galvanic corrosion susceptibility and forecast corrosion extent based on environmental factors.
Selecting materials for structures or vehicles such as aircraft based on measured galvanic corrosion rates in relevant environmental electrolyte conditions.
Determining optimal replacement times for materials to prevent equipment failure by monitoring galvanic corrosion rates with the instrument.
Examining influence of environmental conditions like relative humidity, temperature, and pollutant chemistry on atmospheric corrosion kinetics using controlled environmental chambers.
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