What is a Corrosion Coupon?
A corrosion couponis a key instrument used to determine the corrosion rate of pipelines in various industries. In industries such as oil and gas, pipes can easily rust or be damaged by rust. This is where corrosion coupons come into play.
The process involves inserting a sample (called a coupon) into the tube for a specific duration. After this period of time, the coupons are retrieved for inspection. The basic measurement obtained from these corroded rolls is weight loss, which occurs as a result of the material rusting.
The use of corrosion coupons allows operators to understand the extent of corrosion in the pipeline. The weight loss data on the coupons provides valuable insight into how quickly rust can occur. With this information, the operator can then decide on the right action to take to slow down the rusting process.
This method of using corrosion coupons helps to effectively manage and mitigate the effects of corrosion. As a result, the service life of the pipeline can be extended and its operational efficiency and reliability can be maintained.
Calculate the Corrosion Rate
By reducing the sample weight, one can calculate the corrosion rate using a straightforward ASTM formula:
V: Corrosion rate (μm/year)
M∆: Sample weight change (mg)
ρ: Alloy density (g/cm3)
S: Sample area exposed to the environment (cm2)
t: Duration of exposure (h)
K: Fixed coefficient (106*8.76، With units used for other terms)
Corrosion coupons come in various forms and types. They can be rectangular, round, or spiral in shape, and can be either standard or prestressed. The size of the patch does not usually affect the accuracy of the reading, as the most important factor is the surface area exposed to the environment. The larger the exposure area, the faster and more accurate the reading will be.
Weight reduction and corrosion coupons can be made of any material. However, they tend to be made of environmentally friendly materials (such as those in the pipeline or storage tank under test) or mild steel, which are prone to rust. If you want to replicate the corrosion that occurs in a particular pipe, it is best to use coupons made of the same material.
A mild steel coupon can be used to check whether the corrosion inhibitor forms a protective film. However, it is important to remember that even if these liners prevent corrosion, this does not necessarily mean that the corrosion rate of the actual pipe will be affected in the same way.
Strip Corrosion Coupon
These coupons have two holes for connecting, so they can be used for many different tests. They are used extensively in various types of equipment to check for rust. These joints are usually placed where the pipe opening is narrow or the equipment pressure is low.
The type of coupon that is used the most is usually called a bar coupon. It comes in different sizes and is often available in the following measurements: 3″×3/4″×1/16″；3″×1/2″ ×1/16″
Disc Corrosion Coupon
Disc corrosion test is a tool used to check for rust. These are usually used in pipes where the face of the note cannot stick out into the pipe as it could disrupt the flow of anything in the pipe. This method can also be used when you want to check for rust in multiple places at the same time.
The disc corrosion test has a hole that can be removed. To fit it in place, you need a screw, a special washer, and a non-conductive disc.
Corrosion coupons are indispensable tools for accurately monitoring corrosion rates, reducing maintenance costs, measuring material degradation and determining equipment service life. They provide valuable data on the life of materials and help prevent scaling in pipes, Wells and injection molding lines. Corrosion coupons offer several advantages for monitoring and mitigating corrosion in a variety of industrial environments. Here is a simple summary of the benefits of the rewrite:
- Affordable and Reliable: Corrosion coupons are relatively inexpensive and provide reliable results in terms of weight loss. They are less prone to tool failure compared to electronic corrosion monitoring methods.
- Versatile Application: These coupons can be used in all environments, including gases, liquids, and solids and particles.
- Insightful Analysis: They allow for visual inspection, observation, and analysis of corrosion deposits. The weight loss can be easily determined, and the corrosion rate can be easily calculated from this.
- Corrosion Identification and Inhibitor Performance: They help identify local corrosion and measure the performance of corrosion inhibitors.
- Online Corrosion Coupons: These are used in critical process circuits to evaluate fluid corrosion. Commonly, alloy steel and carbon steel coupons are used for this purpose.
- Assessing Fluid Corrosion: The corrosive nature of the fluid can be assessed based on the corrosion rate of the coupons. This information can be used to optimize the number of additives used in the process.
- Coupon Monitoring and Material Selection: Coupons are useful in environments where corrosion rates don’t change much over time. They can complement other techniques, such as electrical resistance and linear polarization resistance methods. They also help in choosing materials for new pipes, tanks, or ships by testing different alloys under the same conditions.
- Confirmation of Probe Readings: Coupons should always be used to confirm probe readings and to validate long-term corrosion rates.
What is the method of applying corrosion coupons?
- Simple and Clear Testing: Corrosion coupons are easy to use. You weigh them, put them in the area you want to test, take them out, clean them, and weigh them again. The change in weight shows how much material was lost to corrosion.
- Standardized Way of Measuring: The NACE, a well-known organization for corrosion professionals, gives a standard way to calculate weight loss. Most people use miles per year (MPY) to talk about this.
- Works Well with Other Methods: You can use corrosion coupons with other tools like electrical resistance probes and online analyzers, which continuously check the pH, iron, and chloride levels.
- Made from Many Materials: Corrosion coupons can be made from any material that’s widely sold, giving you lots of options.
- Can Study Different Types of Corrosion: By changing the shape of the coupon, you can study different types of corrosion, like galvanic corrosion (when two different metals touch) and aeration cell corrosion (from oxygen in water).
- Works with Different Holders: Coupon holders can hold different types of coupons. This is useful in pressurized containers like tanks, pipelines, and oil wells.
- Easy to Install: You can put coupons in any direction that works for your project.
- Quick Detection: If you put a coupon in a pipeline, you can quickly see how much material it’s losing.
- Reacts Fast to Corrosion: Coupons made of active metals like zinc or aluminum react quickly to corrosion, so you’ll know sooner if there’s a problem.
- Can Be Tested First: You can test coupons in a special container that mimics the conditions they’ll be in. This lets you see how they’ll work before you actually use them.
We offer a wide range of corrosion coupons specifically designed to meet diverse corrosion monitoring needs. We invite you to contact us to find a solution that best fits your requirements.
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Packaging & Delivery
Our products are packaged in cases, which offer the following benefits:
- They are lightweight, feature clean lines, provide insulation, and boast high strength without susceptibility to deformation.
- They eliminate the need for fumigation, making the shipping process more efficient.
Our commitment is to deliver top-quality corrosion coupons promptly and efficiently, prioritizing customer satisfaction at all times.