Oxygen is one of the most destructive forces in modern society, especially because we build and manufacture using metals. From rusting iron rebar, to stress corrosion cracking on aluminum hulled craft, to the extremely corrosion resistant nickel alloys used for potential nuclear waste storage, corrosion happens.
Gamry has been at the forefront of electrochemical corrosion testing since our inception in 1989. Read on to learn more about corrosion research and how Gamry people and systems fit in.
Corrosion is the chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the metal and its properties (see ASTM G 15). A chemist would classify corrosion as an oxidation, an electron-transfer reaction involving the loss of electrons.
Since corrosion is an electrochemical process, it follows that electrochemical techniques and electrochemical instrumentation can be used to study the corrosion process. Indeed, a number of electrochemical techniques have been developed over the years especially for the measurement of corrosion processes. Electrochemical techniques are very well accepted by the corrosion community and it is the rare corrosion laboratory that does not make routine use of these tools.
The reasons for the popularity of electrochemical techniques for corrosion measurement are based in practicality:
They are fast. Corrosion, even rapid corrosion, is a slow process. Real-time weight loss measurements need days and sometimes weeks to make a reliable measurement of corrosion rate. Electrochemical instrumentation can make a corrosion rate measurement in minutes or hours.
They are sensitive. Modern, well-designed electrochemical instrumentation can measure extremely low corrosion rates.
They are accurate. Electrochemical techniques have been exhaustively tested before finding general acceptance. Organizations such as ASTM and NACE have sponsored a number of symposia and published peer-reviewed papers describing the use and results of these techniques.
They are versatile. Electrochemical techniques can be used to study a wide range of corrosion-related phenomena. The rate of uniform corrosion can be measured. The tendency of a metal to exhibit localized (pitting or crevice) corrosion can be measured. The passivation behavior of a corroding system can be studied. Galvanic corrosion can be quantitated. Sensitization effects can be studied. Electrochemistry can be used in the laboratory or in the field. Measurements can be made on the lab bench or in a pipeline or in an autoclave or in a slow strain rate machine.
Since electrochemistry was recognized many years ago as the basis for corrosion, a number of electrochemical techniques have been developed specifically for corrosion measurement. The techniques breakdown into DC, AC, and Noise.
All Gamry potentiostats can be set up to perform DC, AC, and/or Noise corrosion testing, though for very low corrosion rate systems, the Reference 600 is the best choice due to its superior low current performance. All Gamry potentiostats can also be operated isolated from earth ground (aka floating), making it possible to do testing even when the counter is grounded like in autoclaves.
Gamry offers simple multiple channel testing with our ECM8 Multiplexer which allows for one potentiostat to do the work of 8, and greatly simplifies longer run experiments.
Different techniques are covered under various software packages. Details are available in the software section but briefly:
- The most common DC techniques are part of DC105.
- Critical pitting temperature, which requires some specialty equipment, is available in CPT110.
- EIS300 and EFM140 (a Gamry exclusive) offer AC techniques.
- Electrochemical noise can be done simply with EN120, but is most potent using ESA410.
Gamry also has several electrochemical cells that are good for various corrosion tests (MultiPort, EuroCell, ParaCell, Flexcell). Our VistaShield may also be necessary for studying materials that exhibit very low corrosion rates.
Gamry Instruments has been producing lower cost, electrically isolated potentiostats for corrosion testing since 1989. We have the most comprehensive electrochemical corrosion technique library around, including Gamry developed/exclusive experiments.
We are also very willing to share our expertise with our customers. There are Applications Notes which are relevant to corrosion scientists and engineers. We also have electrochemistry specialists available over email or phone that understand corrosion testing, and can get you pointed in the right direction.
If you are new to corrosion research and electrochemical corrosion testing in particular, you may want to start with a quick look at our Application Note on DC Corrosion Techniques, and consider enrolling in a short course like the one taught at Pennsylvania State University every summer. For those who are already familiar with the corrosion process, please have a look at our Application Notes covering Electrochemical Impedance Spectroscopy, and consider swapping your Rp/Ec Trend out with EFM Trend.