Corrosion Coupon

Description

Corrosion coupon is a simple yet effective tool for providing a quantitative estimation of corrosion rates occurring in an operating system. They also provide a visual indication of the type of corrosion that may be occurring in the monitored system. So if you want to know more about Corrosion Coupon, please contact our professionals to answer them for you.

Common pipeline corrosion types

For a long time, most of the corrosion conditions were not identified as early as possible. Or we identified but failed to handle it properly. Or problems that are directly ignored can lead to corrosion. Corrosion has always been a problem, and it will bring huge economic losses. This is also the main application scenario of our Corrosion Coupon

Pipeline damage

Pipeline damage is usually the first indication of a corrosion problem. However, in many cases, such signs of pipeline damage will be obvious for months or years. It’s just that we’ve been ignoring it.
This damage can be very small (in the form of pinhole leakage). It can also be disastrous. Because no matter whether the water quality is damaged or the pipeline is replaced, it will bring great economic losses.

Pipeline maintenance

There are various forms of pipeline maintenance. In many cases, the consequences of not facing the corrosion problem are serious. That is to face frequent failures or to carry out continuous maintenance. This will waste a lot of valuable time. Therefore, we should face the problem correctly from the very beginning. This will minimize corrosion damage.
The single failure or multiple failure of a part is often due to the failure to find out the hidden causes. Absolute trust will make us relaxed. But this is also a dereliction of duty. It is known from the corrosion rate data provided by the corrosion coupon. The frequently corroded pipeline is contrary to those obvious physical indicators. Such as pipe thread leakage and high rust deposition. High corrosion conditions continue unabated, resulting in more repair problems.

Pipe thread leakage

The thread of each pipe is an inherent weak point. The loss is that about 50% of the pipe wall is cut off. Leakage at the pipe thread is usually the first sign of corrosion problems. This will prompt us to conduct further investigations. And if it is ignored and no solution is taken. Catastrophic water related losses will occur at all pipe intervals.
For the person in charge of a building or factory, the inherent conditions of a large pipeline trunk line are the most worrying. Because they are all threaded pipes. This usually causes the greatest damage. Even if the pipe wall is thick enough to prevent greater damage. However, high pitting conditions will still lead to the failure of any area of the thread. Although in this case, the water may still continue to pass.
Corrosion problems such as small leakage, dissolution of iron oxide and accumulation of other deposits may occur at the pipe thread. At first, they will be reflected on the outer surface of the pipe. However, in fact, this is an internal corrosion problem.
For those threads where the pipe wall is uneven and under high corrosion conditions. The situation is more dangerous. This is because the uniformity of the pipe wall is reduced. They thus fail to provide an indication of leakage problems. All forms of pipe thread leakage. They all have a potential risk of thread failure.

Electrically induced failure

As long as different metals are connected together, electrochemical corrosion may occur. The corrosion degree depends greatly on the corrosion conditions and the pipeline system.
For example, compared to chilled water or fire fighting system water. This corrosion is more common in open condensate and production water systems. This corrosion often occurs between carbon steel pipes and copper valves. The connection between galvanized carbon steel pipe and copper valve is particularly serious. The blue-green deposits at the valve and the connection between the steel pipe and the steel pipe on the reverse side have no leakage. Which provides a condition for current communication. This is a very common and common corrosion behavior. This may lead to large-scale failure and separation of the main pipeline.
In many cases, thread leakage between carbon steel pipe and brass valve or copper pipe is naturally considered to be caused by electro activity. But in fact, it is caused by a larger and more threatening high corrosion problem. In this case, it would be an expensive “misoperation” if the steel pipe was simply replaced with a dielectric insulation fitting. It will lead to long-term, continuous high corrosion behavior and ultimately the failure of the whole system.

Deposits inside the pipeline

The deposits formed by rust inside the pipeline are usually called corrosion nodules. For most pipeline systems, it means the inevitable death penalty. They are light and low-density products produced by corrosion of steel pipes. Once the high and uncontrolled corrosion conditions are determined, the internal deposits will become an induced point causing greater deep pitting.
The most serious corrosion of this kind usually occurs in horizontal pipelines with low flow rate or dead angle. These places are particularly prone to deposit large amounts of sediment. Of course, vertical pipelines and main vertical pipelines will also occur. It’s just that this situation is not so serious.
Although the areas where high corrosion tumors occur are random. But it is actually a direct result of high spot corrosion or battery corrosion. The volume and height of rust deposition are proportional to the depth and volume of pipe wall loss.

Insulation layer failure

This may be contrary to the manufacturer’s statement. Standard glass fiber insulation materials can not provide an effective waterproof and breathable layer for low-temperature pipelines.
Secondary concentration and condensation of water vapor outside the pipeline. This is usually a hidden external corrosion condition. In cold water and dual temperature systems. The external corrosion rate is up to 10 times or more of the internal corrosion rate. For decades, the failure of those hidden insulation layers can destroy the entire pipeline system.
In fact, insulation is not hidden in most cases. Therefore, the failure of insulation layer should be easily identified. The breaking, damage and loss of thermal insulation materials may be a problem worth studying. When the external surface of the insulation pipe shows signs such as deterioration of water quality, dripping of water, discoloration or crystallization of water quality, etc. We should further look for potential corrosion problems.
Aluminum and vinyl jacket can provide less resistance to moisture migration. But at the same time, they also cover up some signs of discoloration. In addition, the surface of the vinyl jacket often condenses more water. This creates a greater threat of corrosion outside the pipeline.
Because the wall thickness of the small diameter pipe is small. So the insulation material used in combination with it will be thinner. Then it becomes the biggest threat to the failure of the insulation layer of the small-diameter pipeline. The low temperature of the water supply in the pipe further increases this threat.

Damage due to weather conditions

In all corrosion forms of the pipeline system. Damage due to weather conditions such as rain, snow, atmospheric conditions, or excessive spray of cooling towers is relatively easy to prevent. Because this kind of pipe is usually exposed to the outside, we can get close to it easily. At the same time, its corrosion behavior is always so obvious. So it’s easy to find with the naked eye.
Most failures due to damage caused by weather conditions take decades to occur. The reason is only due to insufficient maintenance. Of course, small-diameter pipes are still the most vulnerable due to their inherent small wall thickness.

under-deposit corrosion

Under scale corrosion is the most representative and destructive corrosion of pipeline systems. It is often called “galvanic corrosion”. It is characterized by aggressiveness and locality.
Only a small area of the metal surface has corrosion under the scale, which may lead to very deep penetration. This will also cause a large area of corrosion in the surrounding area. Due to the existence of corrosion factors such as surface deposition, uneven potential or other initiation mechanisms. This will lead to erosion of some individual points.
In most cases, pitting will spread over the entire metal surface. Eventually this will result in an irregular or very rough profile of the metal surface. Of course, there are also some individual cases where potholes are concentrated in a specific area. Most of the metal surfaces of the equipment look very new.
Galvanized pipes are more sensitive. Therefore, it is often corroded under the scale under the attack of microorganisms. Whether or not there are potential rust conditions in the internal pipeline. However, once rust is formed, it indicates that there are many potential problems to us in varying degrees.
Under scale corrosion is an inevitable dead angle of pipeline system. Therefore, these deposits are effectively eliminated so that the chemical inhibitor can further reduce the loss of corrosion. We must give priority to this.

Corrosion under insulation

Corrosion under insulation (Cui) is very common. But it is usually hidden. The underlying problem is that we always have a misunderstanding. We think glass fiber and soft foam insulation materials provide a moisture-proof layer. But please do not forget this. That’s why we choose these insulation materials because they can reduce heat transfer. Rather than reducing humidity migration.
Most low-temperature pipelines have the problem of insufficient insulation layer thickness. Or improper material type or improper installation. Even the above three problems exist. The damage and loss of thermal insulation materials will indeed make water migration easier. This is a common and very big problem for those apartments where double insulation and cooling risers are installed outside the building walls. Those buildings with the age of 45 years or more. Except for those who have already replaced the main pipeline at great cost. The other external riser pipes have been almost completely scrapped.
For pipes with small diameter, due to their thin insulation layer and pipe wall thickness. It is more susceptible to corrosion under the insulation layer. The situation of the water supply end pipe will be worse. Because this is affected by the lower surface temperature. In addition, the threaded end adds another hidden danger. This usually occurs on smaller pipes in cold water and double temperature systems.

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