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Determine testing/analysis needs based on area of interest
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Alloy Selection
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Alloy SelectionSelection of materials of construction requires knowledge of: - the corrosion behavior of several candidate materials.
- the mechanical requirements of the components of equipment.
- the corrosivity of the service requirement.
At times, this information may be known from prior service experience or through a survey through the corrosion literature. In other cases it requires the use of lab or field corrosion test methods.
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Failure Analysis
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Failure analysis involves the review of physical information regarding a failure event or a series of failure events with the intent to develop an understanding of the cause. Such studies usually requires a certain degree of knowledge of the following: - System operating history.
- The intended materials of construction
- The chemical nature of the service environment.
Oftentimes, supplemental testing of the materials and the environment are required to verify their properties and chemical nature. In some cases where remedial actions and high reliability are needed, it is common to conduct tests in the laboratory under simulated service conditions.
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Inhibition
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InhibitionInhibition of corrosion involves the addition of a chemical species into the service environment which results in a reduction in the rate of corrosion of the material(s) used in construction. Effective chemical inhibition is usually obtained through one of the following processes: - Filming of the surface by inorganic molecules.
- Reaction or removal of corrosive species in the environment.
- Control of electrochemical potential of the material.
Care should be taken to prevent unexpected results from the use of inhibitors which can, in some cases: - Increase general or pitting corrosion rates of some alloys.
- Produce incompatibility of inhibitors with wither metallic and non-metallic materials in the system.
- Promote fouling, emulsions, environmental or other problems not directly related to corrosion.
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Corrosion Monitoring
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Corrosion MonitoringEvery system which involves the exposure to corrosive environments should have an organized program of corrosion monitoring. Techniques which can be utilized in corrosion monitoring vary greatly depending on the nature of the system and the need for reliability. They are usually aimed at monitoring changes in the severity of service environment, determining the nature of corrosion (i.e. uniform or localized corrosion), or establishing a trend of corrosion rate for use in service life prediction. These techniques can include the following:- Exposure and examination of corrosion coupons.
- Corrosion Problems using electrical resistance or linear polarization methods (or other more sophisticated electrochemical techniques).
- Ultrasonic Testing (UT) of materials thickness or crack growth by SCC.
- Hydrogen Probes (in hydrogen sulfide or other hydrogenating environments).
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