An autoclave is basically a test cell for high-pressure and often high-temperature environments. Autoclaves can be used as static independent autoclaves and as dynamic autoclaves when connected to recirculation loops. Autoclaves as well as test loops can be manufactured from various materials: stainless steel is a standard material but more corrosion resistant materials such as Hastelloy and titanium are used, too. For low-temperature applications, autoclaves can be coated with Teflon.
Autoclave geometry is typically cylindrical, but they can be manufactured in different forms depending on the application. A flow through cell is essentially a tube through which there is a water flow. Electrochemical sensors and corrosion probes are installed through the bottom and top lids.
Low-pressure test cells allow more freedom with the design because a cell does not have to contain the pressure. Test cells for Hydrogen Induced Cracking (HIC) are often large glass walled containers in which tests according to NACE TM0284-11 and TM0177-05 Method B are performed.
Autoclaves can comprise many instruments such as electrochemical tools, electromechanical and servohydraulic loading devices, mixers and rotating electrodes.
Top of Line Corrosion (TLC) instruments are used for studying the corrosion caused by condensed water in a pipeline. Cormet has a versatile TLC instrument with continuous bubbling and a cooled finger-type specimen. Optionally, there is a small funnel under the specimen where water drops condense. This water can be taken out of the autoclave for chemical analysis or electrochemical tests can be performed on line in the funnel.
Hydrogen permeation tests are performed according to ISO 17081:2004(E) using a two cell autoclave with a steel plate between them. A corrosion reaction producing hydrogen takes place in one autoclave. Hydrogen permeates through the steel plate into the other autoclave, where the hydrogen content is measured using an electrochemical method. Cormet has built this kind of instrument for high-pressure high-temperature applications with a loading device applying stress on the steel plate. One can study the effect of pressure, temperature and stress on the hydrogen-permeation kinetics.