Erosion corrosion also known as flow-enhanced corrosion or impingement attack takes place in flowing systems where turbulence occurs and solid particles i.e. sand is associated, typically in pipe bends (elbows), flow constrictions, and other internals, pipe fittings that alter flow direction or velocity.
The mechanism for this type of corrosion is the continual flow of water, which removes any protective film, such as corrosion inhibitor or metal oxide from the metal surface. The exposed surface quickly corroded and the resulting oxide is in turn eroded away.
Erosion is a complex issue; dictated by fluid phase, flow regime, density, solids content, solids hardness, solids geometry and flow-enhanced corrosivity (erosion-corrosion). Erosion corrosion involves a synergistic relationship between erosion and corrosion, where the combined rate of metal loss can be higher than the sum of the rates expected for erosion and corrosion separately.
A related corrosion mechanism is flow-induced corrosion in which the fluid is the erosive component. The corrosion rate of carbon steels increases with increasing mass transfer rate and wall shear stress.
Why Is It Important to Control Erosion Corrosion?
Managing erosion corrosion is essential because this form of damage can quickly weaken industrial systems that transport or process fluids. Unlike ordinary corrosion, which develops gradually, erosion corrosion accelerates material loss as protective surface films are repeatedly stripped away by fast-moving liquids, abrasive particles, or entrained gas bubbles.
If not addressed in time, erosion corrosion can create serious challenges, such as:
- Unexpected Failures: Rapid wall thinning may result in leaks, bursts, or equipment collapse.
- Increased Operating Costs: Frequent part replacements and repairs raise maintenance budgets.
- Production Interruptions: Equipment breakdowns lead to costly downtime and reduced efficiency.
- Workplace Safety Risks: Damaged pipelines or vessels carrying oil, gas, or chemicals can endanger workers.
- Environmental Harm: Uncontrolled leaks may contaminate surrounding waters or ecosystems.
Proactive measures—such as selecting resistant materials, applying protective coatings, optimizing flow design, and performing routine inspections—are the best defense against erosion corrosion.
Erosion corrosion
Erosion corrosion can lead to rapid failure. The primary method of avoiding erosion and erosion-corrosion is to design facilities with velocities below the limit given by API Recommended Practice 14E. Although this limit is known to be conservative in most cases, it provides a reliable design that is tolerant of design changes and unexpectedly erosive flows (e.g. from slugs of solids). However, it is only applicable to straight pipe and does not consider geometry or entrapped solids.
Sand production has been considered in design basis. Presence of solid or sand in the system is considered as a major threat if not properly mitigated. It may cause erosion corrosion and plugging the facilities that will reduce the mechanical integrity of the facilities.
Material selection is affected by sand and harder material for valve sheets is provided to minimize erosion. The design of piping should also taking into consideration to evaluate the possibility of using thicker pipe or additional corrosion allowance, using long radius bends, etc. Erosion resistant materials, such as cermet’s (tungsten carbides with metallic binder) or ceramics can be applied as coatings on local parts of the system being most exposed to erosion.
The threat also can be reduced by installing sand jetting system in production separator and sand handling facilities downstream of production separator so that the sand can be prevented from entering to all systems. Unlike copper alloys, stainless steels generally offer very good resistance to impingement attack.
Higher surface hardness of 22Cr or 25Cr DSS compared to austenitic stainless steels (i.e. SS 316L) can in some cases be an advantage.
Sand monitoring should be performed in order to control the sand production effectively. Inspection of the most exposed components to erosion is recommended to be performed regularly to control the material degradation.
Frequently Asked Questions (FAQs) on Erosion Corrosion
1. What exactly is erosion corrosion?
Erosion corrosion is the combined effect of rapid fluid movement and chemical attack that gradually strips away protective surface films, leaving the material vulnerable to wear and thinning.
2. What triggers erosion corrosion in equipment?
It usually arises from high-velocity liquids or gases, suspended particles, bubbles, or aggressive chemicals that continuously impact the surface, accelerating metal loss.
3. Which sectors face the biggest challenges with erosion corrosion?
Oil and gas operations, power plants, chemical facilities, marine systems, and desalination units often deal with this issue due to harsh fluids and abrasive environments.
4. How can erosion corrosion be minimized?
Effective strategies include lowering fluid velocity, optimizing pipe layout to reduce turbulence, applying protective coatings, using corrosion inhibitors, or switching to more durable materials.
5. What materials stand up best against erosion corrosion?
Alloys such as duplex stainless steels, titanium, nickel-based alloys, and even ceramics are favored for their durability, depending on the fluid composition and service conditions.
6. How do engineers detect erosion corrosion in practice?
Specialists rely on routine monitoring, including ultrasonic thickness testing, corrosion probes, and visual checks, to identify early signs of thinning before failures occur.
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