August 2016, Vol. 243, No. 8


Integrated Corrosion Management of Oil, Gas Installations

By Tata L.N. Murthy, Andhra Pradesh, India

Corrosion monitoring of oil and gas installation usually peaks during the operations/production stage, but each stage of the project is (design, construction, commissioning, operations, maintenance/shutdown time) is equally important for these facilities. The activities carried out during the design/commissioning stages are necessary for efficient production because corrosion monitoring will be carried out once the facilities are in operation.

Compare corrosion monitoring to the watchful eyes of an eagle: macro to minor, nothing is too small to be ignored. This article discusses the importance of design, construction, commissioning, operations and shutdown activities along with the role of corrosion monitoring.

Corrosion Monitoring Requirements


This is the main phase in any project. If the utmost care is taken during design nearly a third of the corrosion problems can be resolved. Analyzing fluid characteristics and selection of suitable alloys as per requirements are very important.

In the case of external pipeline coating, a better coating can be selected depending on the soil resistivity and ground characteristics. Proper selection of the internal coating can also solve many internal corrosion problems. This stage, too, is critical in the case of corrosion-monitoring instruments because if something goes wrong here, it will considerably affect the later stages. Conferring with material, cathodic protection and coating specialists during the design stage adds more value to the project.


People will take the utmost care in coating the pipeline, but this coating should remain carefully watched up to the burying of the pipeline Normally unskilled people will lift the pipeline with wires or chains in some places. Similarly, at the time of earth filling, workers will throw soil in along with stones. This will spoil the coating and in later stages, create hot spots of corrosion. When leveling the pipeline during the burial process, the pipeline engineer should consider the pits, which are being filled with new soil. In the rainy season this will shrink and cause the pipeline to be exposed  as the lack of proper support is putting stress on the pipe.  This may lead to stress corrosion cracking (SCC).

Sample points will be fixed at the time of design and construction. Normally at this stage no chemist or chemical treatment people will be available. Only after production starts up will these people begin corrosion monitoring and they may find some difficulty with sample points. The main problem may be that there are fewer sample points to check for corrosivity or other corrosion-monitoring activities. The sample points may be in the wrong position or there may be no sample points in key locations. The corrosion-monitoring team must then rely on the existing facilities for doing corrosion tests though this may not provide complete data for decision making. This ultimately will have a strong impact on the system which can lead to undetectable corrosion problems and failures.

Normally buried pipelines may not have sample points in ideal places to collect data. A sample point at the 6 o’clock position is required to get data. Pits should be constructed for these buried lines. There is a need to discuss with chemical treatment and corrosion-monitoring personnel at the time of design and construction to plan for a better facility to corrosion monitoring.


Utmost care must be taken here as priority will be given to the production start-up. The corrosion-monitoring systems’ functionality needs to be checked with the vendor at this point


In this phase corrosion monitoring really needs to be watched over with an eagle’s eye where everything is viewable (Figure 2). An eagle can observe an entire village from the sky and can observe a small creature that it can also catch. Similarly, corrosion-monitoring systems should watch the entire facility plant to a minute level.

In many places, people are solely dependent on coupons. Although this is a good technique, it will not help in preventing corrosion. For example, one coupon is showing a corrosion rate of 5 MPY (mille inches per year). That means corrosion has already happened at the rate of 5 MPY in the pipeline from where the coupon is retrieved.

Despite coupons having the latest corrosion-monitoring technology thanks to newly developed instruments and user-friendly software, corrosion can still exist although there is no reason why it should. These coupons should be in used addition to probes and as a secondary corrosion-monitoring device. The data released should meet the expectations of the corrosion engineer.

Corrosion monitoring specialists need to concentrate more on preventing corrosion. They have to forget about the failure analysis. Getting real-time data does help them in preventing corrosion. But technology has advanced and anyone can know understand the issue with this newly developed corrosion-monitoring instrumentation. Techniques like LPR (Linear Polarization Resistance), EIS (Electrochemical Impedance Spectroscopy) and ER (Electrical Resistance) should be implemented to get data for preventing corrosion. Many people will study corrosion monitoring but only a few are doing corrosion monitoring for real-time data.

Pigging water is the main source for identifying the actual condition of the pipeline. Normally there is less interest in collecting pigging water samples. The pigging water has different characteristics and composition from start to end. The sample should be a homogenous mixture of all these materials. If not, the data will not be useful and may misguide workers.

Many lines often have probes – coupons with a fixing point at 12 o’ clock position only – because this will facilitate easy removal and easy access for readings. To some extent in gas lines, the probe and coupon location won’t make much difference. However, this will make a big difference in wet crude lines. Normally in wet crude lines, free water will be located downside of the line due to the high specific gravity of water when compared to crude. The main culprit for corrosion in any line is water, if this water is having corrosivity. The probe or coupon located in the 12 o’clock position, cannot catch that and in fact, gives the wrong guidance. Probes and coupons should be fixed in the 6 o’clock position for better results.

A corrosion-monitoring team will spend considerable time collecting data, but will pay little attention to the analysis even though this and the interpretation of the results, is essential for decision-making. Quality-control tools like control charts, bar charts, trend charts, fish bone diagrams etc., help with data analysis. Microsoft Excel can be used for preparation graphs. Today many good software packages are able to shorten the time for data analysis.

Many companies will not conduct audits by corrosion experts. They prefer to call experts only after a major failure. It is far better to have a corrosion audit by a team of experts in a periodic manner. Many companies generally prefer to conduct audits\, where there are statutory or legislative requirements.


During the maintenance/shutdown stage, workers need to wash the separators and vessels which are coated with sand produced from the wells. While their main interest is to just get rid of the sand, for which they will use firewater, this is full of bacteria, and the washing process will contaminate the separators. After production starts up, the temperature conditions are conducive to allow the bacteria to begin to develop in the system. Because the direction of flow is toward the storage tanks, the tanks will also be contaminated. Normally, this is the only difficult system in the oil and gas production facility that needs to be treated for bacteria.

The water using for washing the inner part of oil and gas production operations should be treated with biocides, scale inhibitors and corrosion inhibitors. Extra care needs to be taken while washing to avoid contaminating the inner side of the separators, lines, wash tanks, etc.

Almost every plant will periodically conduct ultrasonic thickness surveys for their pipelines, separators, tanks, process facilities, etc. That’s when they should also check underneath the insulation. Normally insulation will be kept for low temperature and high temperature lines or vessels. The measurement team will cut a small portion of this insulation and to take reading and they will close that patch within few hours or days. During this exposed period moisture with high oxygen will ingress into the insulation. The insulation material will be saturated with moisture and oxygen. This material will be in direct touch with the pipeline. This will cause severe corrosion problem, which cannot be directly seen also. This may also cause many types of corrosion failures such as microbiologically induced corrosion (MIC).


Appropriate corrosion monitoring at each stage of a project is critical to protect very expensive oil and gas installations.

Author: Tata LN Murthy is a chemist and internal corrosion specialist working in India at Gujarat State Petroleum Corp.’s onshore gas terminal as an assistant general manager.  He has 14 years of oil/gas laboratory and corrosion experience.


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