Most assets depreciate, losing value over time as a result of wear and tear, age, or ob-solescence. Corrosion, like

depreciation, results in the often hid-den cost of a non-cash expense — mea-surable in terms of reduced operating life — that reduces the value of as-sets. Many engineers in the chemical process industries (CPI) see corrosion on a “straight-line basis” in terms of repair, maintenance and replacement during fixed-interval turnaround in-spections. New technology, however, can assess corrosion deterioration in realtime, using the plant control-and-automation system.

The latest technology links corro-sion to process conditions more di-rectly and immediately. It also allows corrosion depreciation to be assessed in much-shorter time intervals with the ability to control and mitigate the rate of damage, and more accurately factor-in its true economic impact on plant operations.

Illustrating the importance of cor-rosion depreciation is the fact that corrosive attack leads to plant break-downs with some very considerable costs. Consider these figures based on recent studies:• The annual cost of corrosion in the

U.S. is estimated to be about $300 billion (about 4% of the gross domes-tic product)

• For the petrochemical and pharma-ceutical sectors, the annual cost is about $2.5 billion

• The annual corrosion cost in the CPI is over 10% of the annual plant capi-tal expenditures across these indus-trial sectors

• Globally, the cost of corrosion in the CPI appears to be about $50 billion per year and is projected to climb still higher over the next five years

Indeed, corrosion gives a whole new meaning to the term “depreciation,” particularly when both immediate- and longer-term effects of corrosion are considered.

Still, to many CPI engineers, corro-sion is simply a routine part of plant operations and a cost of doing busi-ness. A corrosion specialist is called when a problem arises. Once the prob-lem is solved, the plant operates more or less as before, until the next upset occurs. The major impact of corrosion to the business lies in costs associated with lost production, health, safety and environmental issues, and legal liabilities.

New technology allows corrosion monitoring via the plant distributed control system (DCS), whereby corro-

sion measurement is coupled to a suite of key, realtime process variables. This process can lead to gains in many parts of the corporate balance sheet.

Process optimization often brings an immediate reduction in direct costs and also helps increase plant produc-tivity and revenues while minimizing corrosion damage. Ultimately, it can provide major gains through reduced “corrosion depreciation allowance” and increased plant asset life.

Staying ahead of the damageIn many regards, the corrosion engi-neer’s job is viewed as that of a histori-cal record keeper. This is because tradi-tionally, the tasks to measure corrosion damage have been documented over relatively long time intervals — typi-

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34 ChemiCal engineering www.Che.Com June 2007

Cover Story

A New Approach to Corrosion MonitoringRussell D. KaneHoneywell Process Solutions The impact of corrosion on assets and processes

is great. Advances in technology allow engineers to assess corrosion in a whole new way, with realtime monitoring and the ability

to link deterioration with process conditions

Figure 1. These data, which depict realtime corrosion data on a hydrocarbon/water stream, show that the rate of corrosion is not steady over time. Peak corrosion episodes occur

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cally months to years — using corro-sion coupons and periodic inspections. This historical information is then used to confirm or predict the effective-ness of corrosion control measures, the risk of future failures, and the need for maintenance. This approach, however, has a major limitation.

Modern plant operations are likely to encounter changes in feed, process conditions and control limits that are based on current market conditions. In one recent case, a plant feed changed every two-to-three days based on de-liveries of particular constituents, which were being purchased on a global basis and influenced by market prices. Unfortunately, these constitu-ents also had widely varying impurity levels that led to corrosivity changes, which made historical corrosion mea-surement worthless.

Now, however, emergence of online,

realtime corrosion monitoring can im-prove the relevance of corrosion mea-surements. This approach reduces the manual effort and the high expenses required to obtain this information. Most importantly, corrosion informa-tion can be obtained quickly — some-times in a matter of minutes — and in a manner consistent with that used for collecting other key process data.

This new approach utilizes exist-ing data acquisition and automation systems found in production facilities. For example, the plant DCS is used to monitor and control processes, trend key process information, and manage and optimize system productivity. Cor-rosion monitoring can be integrated into this system, and the data can be automated and viewed with other process variables (PVs). Advantages of this approach over stand-alone sys-tems include the following:

• more cost effectiveness• less manual labor to accomplish

key tasks• a greater degree of integration with

in-place systems to record, control and optimize

• efficient distribution of important information (corrosion and process data, related work instructions and follow-up reports) among different groups required for increased work efficiency and ease of documentation

The rate of corrosionThe perception of constant-rate corrosion. In field and plant opera-tions, corrosion is typically viewed as the difference between two mea-surements performed over a rather long interval of time. These corrosion measurements commonly come from measured changes in metal thickness (such as from ultrasonic inspection readings made on components and electrical-resistance measurements taken by probe elements) or mass-loss readings (such as weight-loss of coupons). The measurements are taken on the order of weeks, months or sometimes years.

There are two major shortcomings to this approach: data indicate cor-rosion only after the damage has ac-cumulated, and they provide only an average rate-of-metal loss during the measurement interval. Peak corro-sion rates are not documented and, most importantly, the specific time pe-riods of peak corrosion rates and the corresponding process conditions are not identified.

This scenario has led to the gener-ally held misconception that corrosion in chemical processes occurs at a rela-tively constant rate over time. In real-ity, a majority of corrosion experiences in these processes actually occurs dur-ing short periods when specific process conditions develop. Actual monitoring shows peak corrosion rates. An example of this effect is shown in Figures 1 and 2. The data was obtained from a study conducted by the U.S. Dept. of Energy to identify “best practice” corrosion-measurement techniques for corro-sion monitoring [1,2]. In this case, the environments were primarily oil (with varying water fraction, as may

ChemiCal engineering www.Che.Com June 2007 35

Figure 2. Realtime corrosion data in a dehydrated hydrocarbon-gas stream shows six episodes of corrosion over two months (upper graph). The bottom plot highlights a shorter interval to reveal the detail of a single upset that is likely related to upsets in dehydration

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occur during normal production con-ditions) and “dehydrated” hydrocar-bon gas.

The system was monitored with re-altime corrosion measurements using electrochemical techniques and probes that were specifically selected for their compatibility with these “low-water” environments. The data were obtained with a totally remote and automated corrosion-measurement system that involves multiple electrochemical tech-niques, solar power and wireless data telemetry back to a control center.

The data in Figure 1 shows that the corrosion rate was mostly minimal over an approximately two-month pe-riod. However, there were about 20 ep-isodes of high corrosion rate (corrosion upsets that were one to two orders of magnitude above baseline levels) dur-ing this period. Generally, the trend in corrosion rates increased with water content, but it is clear that water con-tent was not the only factor — another variable was likely in play. In oil/water systems, periodically stratified flow conditions can develop at low flow-rates where the water separates from the oil. This can lead to an increase in corrosion activity, particularly at the six o’clock position in piping. In this case, the realtime corrosion measure-ment was more reflective of corrosion upsets than the infrequent process monitoring being performed.

A similar situation was found for a reportedly “dehydrated” gas stream that was susceptible to periodic dew-point conditions due to plant upsets. Figure 2 shows electrochemical moni-toring data from a dehydrated hy-drocarbon gas stream. During a two-month period, six episodes of higher corrosion rate were observed. Whereas the magnitude of the corrosion excur-sions was not as great as in the oil/brine system, the excursions do consti-tute periodic and significant increases in corrosivity, particularly since cor-rosion allowances are typically much smaller in these “dry” systems.

These cases highlight situations that could be remedied by better pro-cess control (separation, dehydration and/or flow control), or more effec-tive dosing of inhibitors at intervals defined by the realtime corrosion measurement, rather than based on

historical, average corrosion rates. A related condition in many gas streams is the need to maintain inlet gas qual-ity to reduce out-of-specification con-ditions from moisture, CO2 or H2S.

Understanding the techniquesOffline measurement. Corrosion coupons have been the backbone of industrial corrosion monitoring for more than 50 years. Coupons must be pre-weighed, distributed to remote lo-cations, installed, retrieved, examined, cleaned and re-weighed before data are processed. Therefore, a good deal of cor-rosion engineering and related techni-cal-staff time is consumed with manual and often routine tasks, as well as with manipulating and viewing historically averaged, offline data. Coupon mea-surements are offline, labor intensive and not easily configured for automa-tion and control systems.

Approaching corrosion assess-ment from an automation and con-trol point of view frees up staff time. Rather than spending time manually retrieving corrosion data, personnel can, for example, use their time to examine, interpret and understand critical underlying system attributes and relationships. Online measurement. In some cases, corrosion probes used to monitor indus-trial plants and pipelines are connected to field dataloggers that take corro-sion-rate measurements over a period of weeks or months. This approach is often referred to by corrosion engineers as “online monitoring” despite the fact the data cannot be accessed, viewed or acted upon in an online, realtime man-ner. These techniques can retrospec-tively identify peak corrosion rates and time periods.

Corrosion probe data using conven-tional methods are, however, typically considered qualitative, at best, due to limitations in the 1960’s measurement techniques used in most field instru-ments. This information is viewed in isolation, without the PVs that allow its interpretation (PVs that relate to periods of corrosion upsets). It is therefore up to the corrosion engineer to locate and piece together relevant process information and manually build correlations to understand the causes of corrosion upsets.

With these remote online measure-ments, technical staff often travel to the remote locations in order to re-trieve corrosion data files. Then, they manually analyze the logged data. Under these conditions, the corrosion engineer is viewed as a bearer of bad news, because the information is usu-ally available only after the damage has occurred or, even worse, after criti-cal failures have taken place.

The current perception is that there is a high “per-point” cost associated with conventional corrosion monitor-ing approaches, largely due to the high cost of a separate infrastructure and large commitment of time and labor. Additionally, there is a low perceived value because the data is historical and is viewed weeks and months past due. Given this perception, there is a tendency to limit resources for corro-sion monitoring because the approach is expensive with only a limited chance of success. In many cases, problems are viewed after the fact, and there is no way to directly link cause and effect in a time frame that allows the dam-age to be cost effectively prevented or minimized. Accordingly, corrosion measurement is relegated to mainly a confirmational reading of second-ary importance rather than a primary variable that can be controlled and op-timized with the process.

This perception is somewhat sur-prising. Many plant operators are trying to squeeze out a 1–2% improve-ment in efficiency and productivity. Corrosion costs are, however, one of the few areas where double-digit cost-reduction improvements could be ob-tained, particularly if lost production opportunity is included.

Estimates indicate that between 25 and 40% of the approximately $300 billion lost to corrosion in the U.S. each year could be saved with better control efforts. In several petrochemical cases (such as fractionator overhead and hydroprocessing), the cost of a single corrosion failure can be in the range of $35 million to $60 million [3]. Even a few days of lost production can involve over $500,000 in losses. Online, realtime measurement. Feedback from realtime corrosion-rate data and adjusted chemical dos-age can offer additional gains in ef-

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36 ChemiCal engineering www.Che.Com June 2007

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ficiency and reduced operating costs, as well as extended run time. Fur-ther confirmation of the potential cost savings — reaped through better and faster corrosion information and implementation of improved process controls — are apparent in the recent U.S. Cost of Corrosion Study [4] and referenced in recent NACE technical committee reports [5].

Corrosion monitoring has developed from a manual, offline process to an on-line, realtime measurement (Figure 3). The initial driving force for this migra-tion is the benefit of automation; that is, reduced time and effort to obtain corrosion data with high data reliabil-ity. Corrosion monitoring takes on new meaning when it can be viewed at a higher frequency (within minutes) that is consistent with the way process vari-ables are measured. More data bring increased statistical relevance, quicker response time, and a greater ability to understand corrosion in the context of the process being monitored.

The second driver for this migration is the ability to integrate the corrosion data immediately with process data. This is done in an automated man-ner, within the plant DCS, rather than by the manual methods traditionally available to the corrosion engineer. Some of the usual PVs that are used and measured in CPI control systems include the following: temperature; pressure; flowrate; chemical injection rate; moisture content; valve actua-tion (opening/closing); level measure-

ment; and analytical data, such as pH, dissolved oxygen and others.

One historical barrier to integrat-ing corrosion measurements within the plant DCS is that online corrosion measurements have been qualitative rather than quantitative due to limi-tations of single technique transmit-ters with limited on-board processing capacity. For use as a process vari-able, corrosion measurements need to be quantitative, since the system will utilize the data to make automated assessments, generate alarms, and determine the economic consequences of process changes and/or upsets. With this requirement also comes the concomitant need to accurately assess corrosion modality (such as general corrosion, pitting, local area attack).

It is generally accepted that there is no perfect method for assessing all corrosion mechanisms. In most cases, however, corrosion involves electron transfer in an electrically conductive local or bulk environment. It has been shown that electrochemical methods can be used to monitor corrosion for dew point conditions, many multi-phase (oil/water) conditions with as little as 1–2% water, and even some fireside high-temperature corrosion situations in fossil-fueled boilers and waste incineration [6–11]. Therefore, if properly used, accurate corrosion mea-surements can be made in a matter of minutes in most chemical processes.

One recently released multivari-able corrosion transmitter employs a

Figure 3. Corrosion monitoring has evolved from offline to online, and online, realtime measurements

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34-41 CHE 6-07.indd 37 5/25/07 4:31:30 PM

suite of automated elec-trochemical techniques that run in the on-board memory of a single trans-mitter and are used to complement one another. This transmitter gener-ates general corrosion-rate data by combining Linear Polarization Re-sistance (LPR) and Har-monic Distortion Analy-sis (HDA) for greater corrosion-rate accuracy. The transmitter also provides completely new information obtained on the localized nature of corrosion from Electro-chemical Noise (ECN) measurements. When joined in an automated cycle, these techniques can provide two critical, operator-level corrosion PVs at a similar frequency of measurement as expected for cur-rent process variables. These opera-tor-level corrosion PVs are:• Corrosion rate: LPR corrosion rate

adjusted for a measured B value (see below) determined by HDA

• Pitting factor: Derived from ECN and LPR measurements, providing a three-decade logarithmic scale rang-ing from general corrosion, through a cautionary zone, to localized pit-ting corrosion

Two additional PVs can also be pro-vided through the process control sys-tem for specialist observation, diag-nostics and intervention:• B value: Also called the Stern Geary

constant, the B value is derived from HDA involving the realtime mea-surement of the anodic and cathodic Tafel slopes. This value is used to adjust the LPR corrosion rates with the electrochemical processes in the system

• Corrosion Mechanism Indica-tor (CMI): Indicating conditions and trends of passivity in stain-less alloys, corrosion inhibition or scale formation

In addition to these types of realtime measurements, there may be a need to include other online-compatible mea-surements into the process-control and automation system, when they

can bring additional value or longer-term corroboration for uses in asset assessment and integrity evaluation.

These corrosion assessment tech-niques are even more attractive if they can be easily automated and cou-pled with the modern communication methods such as wireless technologies. Techniques include electrical-resis-tance-corrosion measurements, ultra-sonic thickness, pulsed-eddy current and fiber-optic strain measurement, as well as other ancillary techniques that may become available as these complementary technologies develop.

ImplementationIn a modern chemical operation, the entire facility is controlled by automa-tion and control systems. The arrange-ments of process equipment, vessels and piping are far too complex for operators to personally control every aspect of their operations. Therefore, they rely on a system of data acquisi-tion and associated computer routines and applications to analyze the data and apply rule-based methodologies for assessing variations in process conditions and prioritizing responses. In modern industrial environments, these systems also provide manage-ment of safety and security. This infra-structure has vastly improved chemi-cal plant productivity.

In the 1970s, when process automa-

tion-and-control technologies were first employed, chemical plants operated at about 70% of daily productivity levels. With newer technologies, productivity has progressed to over 90%. With cur-rent technology and initiatives such as abnormal situation management, the goals are to increase the number of operating days per year and increase productivity levels to over 95%.

A 2004 survey indicates that corro-sion is by far the major factor account-ing for chemical plant failures (Figure 4). Comparing the 2004 survey results with data from a similar 1984 sur-vey shows the situation appears un-changed over the past 20 years. There-fore, it is a foregone conclusion that a more proactive (realtime) approach to corrosion mitigation is needed. This approach must integrate into automa-tion and control strategies if the above-mentioned productivity goals are to be achieved while keeping a critical eye on plant reliability and safety [12].

Examples of integrating corrosion into the process-control environment, where data is displayed in the sys-tem historian together with other key performance indicators (KPI’s), are shown in Figures 5 and 6. In Figure 5, the screen shows the major parame-ters that are normally used to monitor the health of a cooling-water system. The electrochemical corrosion mea-surement captures a corrosion event

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38 ChemiCal engineering www.Che.Com June 2007

Failures245 events

Failures197 events

Figure 4. A 2004 survey of causes for failure in refining and petrochemical plants in Japan shows that a majority of the failures were due to corrosion (left chart). The right side shows failures by type of material of construction

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where the LPR/HDA corrosion rates jump when the blowdown occurs. It is also demonstrated that a large in-jection of corrosion inhibitor (as an automated process) decreases the corrosion rates until they returned to normal levels. Figure 6 shows a simi-lar configuration for a lean, amine system reboiler circuit.

Corrosion monitoring in actionAn important aspect of integration with the automation and control sys-tem is the seamless connectivity be-tween varying job functions. An ex-

ample of this integration in a chemical plant is illustrated by Rohm and Haas, Deer Park plant near Houston, Tex. In 2006, Rohm and Haas became one of the early adopters of online corrosion monitoring technology.

At the Deer Park site, the company planned an alloy upgrade of more than $500,000 after failing to determine why two similar chemical units were showing widely different signs of cor-rosion damage. While one of the plants had low corrosion rates, the other cor-roded at very high rates, causing rapid failure of stainless-steel piping.

After traditional monitoring meth-ods proved ineffective, the company installed corrosion transmitters. By communicating via the HART proto-col, the transmitters fed corrosion data directly in the process control system, allowing it to be alarmed, histor-ized, trended and assigned to process groups. With this information, the cor-rosion data was then seamlessly cor-related with other process variables, providing a broader and realtime view of plant operating conditions.

The results benefited both operators and the corrosion experts. Plant oper-ators could access current, actionable process-variable information, includ-ing a time-trended general (uniform) corrosion rate. Additionally, the solu-tion indicated the mode of corrosion (localized or pitting) detection called a pitting factor. Corrosion staff could access the same information with the added capability to review data for di-agnostic purposes.

Using this new system, Rohm and Haas identified two process scenarios that contributed to the difference in corrosion rates. First, one unit’s cor-rosion rate was higher immediately after a shutdown. The company then discovered and replaced a leaky valve that was allowing water into the sys-tem. Secondly, process corrosion was more severe when a particular recir-culation condition occurred. Engineers modified the process, and the plant avoided this condition on the second, more corrosive unit.

The solution saved Rohm and Haas more than $500,000 in capital expen-diture, and the company devised an operating strategy that avoids corro-sion. Additionally, operators utilized realtime corrosion data in combina-tion with process information to im-prove equipment reliability, stability, integrity and uptime.

Whereas corrosion is a known quantity to corrosion engineers, it eludes most operators and process engineers. The above-mentioned example shows how coupling corro-sion data with process data creates a tighter working relationship between corrosion, process engineers and plant operators. Including corrosion as an online process variable makes plant personnel aware of the process

ChemiCal engineering www.Che.Com June 2007 39

Figure 5. This display shows corrosion with other KPIs for a heat exchanger in the plant data historian

Figure 6. In this example, corrosion monitoring is displayed together with other process variables for a lean, amine reboiler line

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conditions that can initiate corrosion. Examples of such conditions include unintentional aeration by venting of equipment to atmosphere, additions of oxidizing agents and aggressive catalysts, lack of dew-point control in normally dehydrated systems, and ex-cessively high velocities in attempts to increase unit productivity.

Online corrosion detection in a pro-cess-control environment will give plant operators immediate feedback on the state of corrosion relative to what they are doing so that they can actively participate in managing ex-cessively high corrosion costs.

New values and insightsIntegration of corrosion with modern, industrial process-control technolo-gies offers substantial operational and cost-saving opportunities for plant operators. Consider the following ex-amples of value propositions obtained from discussions with refinery opera-tions and corrosion personnel:• Increased ability to process crudes

with higher margins — big savings and increased profits

• Reduced cost of unscheduled shut-downs — as an example, a 400,000-bbl/d unit could shut down for three days to repair a corrosion leak. The cost at a $5 margin on feed is $6,000,000. With better integration of corrosion

monitoring and plant economics, the cost of unscheduled shutdowns (due to accelerated corrosion depreciation) can be properly evaluated and consid-ered by plant management. Typically, a plant will have to run at a higher throughput to make up the unplanned short fall

• Improved asset reliability resulting in improved run length — 10% re-duction in maintenance costs

• Improved unit operation as a re-sult of better corrosion monitoring that may result in a 2% increase in throughput, or potentially the ability to process more of a lower- quality feed

• Reduced health, safety and envi-ronmental exposure resulting from fewer unscheduled emissions to the environment — 3% savings

• Improved safety record as a result of fewer shutdowns — 5% reduction in cost

• Savings due to optimized chemical cost resulting from better monitor-ing — 10% reduction

• Increased operator effectiveness by bringing the corrosion data online and in the control room. This leads to improved decision making with new insights and improved issue resolution time

The benefits from the final bullet item can be seen in a recent implementa-

tion of online, realtime corrosion mon-itoring in a hydrocarbon oxidation processing plant [11]. This example involves monitoring performed at a plant where much of the equipment was constructed of carbon steel and 304L and 316L stainless steels.

Decades of debottlenecking and other process modifications led to cor-rosion problems. After a year of unsuc-cessful efforts to untangle material-related problems offline, an online, realtime, electrochemical corrosion-monitoring system was installed. Ma-terials engineers, process engineers, and plant operators saw immediate changes in corrosion behavior caused by specific variations in the process, enabling them to work together to identify process modifications and re-medial actions to substantially reduce damage to equipment.

Based on the results of the initial process evaluation that required only a few weeks, five predominant fac-tors were confidently identified that related to the chemical aggression of the plant environment, which varied substantially with process and opera-tional variables. These included:• An upstream vessel was on an auto-

matic pump-down schedule so that it pumped its contents into a reac-tor approximately once per hour. Every time the vessel pumped down,

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40 ChemiCal engineering www.Che.Com June 2007

New froNtiers: wireless

One potential barrier to rapid acceptance of corrosion as an online PV stems from past practices. Since corrosion mea-surement has traditionally been offline, corrosion-monitor-

ing points that accepted corrosion coupons or probes to be read by data loggers have not been connected to the DCS. There is, therefore, no existing wiring to these points in the plant. In many cases, the cost of the wiring is many times higher than the trans-mitter cost.

Wireless technology, however, is making its way into the plant automation-and-control environment. One approach to this tech-nology is to establish a wireless mesh of monitoring points around the chemical plant. This wireless net is particularly valuable for bringing many new types of information into the plant control-and-automation system. Initially, this new information will be mainly used for diagnostics, documenting work flow, staff safety, and many other non-control functions. This is also likely to be the case for corrosion in its new realtime form.

In this regard, wireless technology is the enabler for setting up a much wider-ranging network of realtime corrosion data points in the process plant than would be possible using conventional wired transmitters. Locations can be dictated by critical need rather than the convenience of wire placement. This expanded network also brings more complete coverage and redundancy. Since corrosion

can be a localized phenomenon, the ability to monitor more lo-cations provides greater assurance that key locations have been included. Data from different probes can also be used to corrobo-rate each other, making the approach to corrosion control more robust than possible with conventional approaches.

After integrating corrosion data with other PVs, existing pro-grams (such as the advanced process-control applications avail-able around the plant DCS) can provide further assessment to identify key relationships between corrosion and other variables. Examples of functions handled in these applications are linear and non-linear modeling capabilities and data-validation tools. These programs provide a means to positively identify single and multi-variant relationships between corrosion and other PVs.

Early event detection is another functionality of the automation and control system, whereby correlations can be made between corrosion and other variables so that the sequence of process events leading to corrosion upsets can be identified. Finally, an important milestone for corrosion as a critical PV is its use in closed-loop, process-control functions. These functions can include multi-variant process control to optimize production while control-ling corrosion within specific operational boundaries, and dosing corrosion inhibitors and other anti-corrosion chemicals, so that the application is based on need rather than historical trends. ❏

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the corrosiveness of the stream increased

• Operators had varied the concentra-tion of a neutralizing chemical in the process. However, contrary to expec-tations, it was found that increasing feedrate of a neutralizer increased corrosion rates rather than reducing them. This new information helped to both reduce corrosion rates and provide chemical engineers with new insight into the chemistry of the process

• Following an initial evaluation of the corrosion data, a plant techni-cian pointed out that an increase in corrosion rate of the 304L occurred right after; they mixed a new batch of catalyst and it varied with fee-drate, which was controlled to mini-mize corrosive attack

• The corrosion rate also varied quite significantly with process and oper-ational events. These included not-ing that the corrosion rate of carbon steel correlated with the quantity of a key gaseous chemicals used in the process

• Short-term spikes to very high cor-rosion rates were observed week after week. The corrosion-rate spikes coincided with the pumping of a laboratory waste stream into the process. Operators changed their procedure to dispose of lab samples another way, thus stopping the cor-rosion spikes

ConclusionCorrosion behavior in process envi-ronments has a number of influenc-ing factors that can vary with time and cause dynamic corrosion events. The long intervals associated with inspections and offline measure-ments do not afford the operator the opportunity to correlate corrosion ex-cursions with operating and process parameters, making control a diffi-cult proposition. By implementing an appropriate and correspondingly dy-namic means of corrosion appraisal, chemical manufacturers can better manage industrial processes and related corrosion prevention treat-ments, minimize corrosion upsets and failures, and maximize the avail-ability of the plant assets. ■� Edited�by�Dorothy�Lozowski

References1. Bullard, S. J., others. “Laboratory Evalua-

tion of an Electrochemical Noise System for Detection of Localized and General Corro-sion of Natural Gas Transmission Pipelines,” Corrosion/2003, Paper No. 03371 (San Diego, Calif., March 17–20, 2003), NACE Interna-tional, Houston, Tex.

2. Covino, Jr., B. S., others. “Evaluation of the Use of Electrochemical Noise Corro-sion Sensors for Natural Gas Transmission Pipelines,” Paper No. 04157, Corrosion/2004 (New Orleans, La., March 28-April 1, 2004), NACE International, Houston Tex., 2004.

3. Kane, R. D., others. “Major Improvement in Reactor Effluent Air Cooler Efficiency,” Hy-drocarbon� Processing, Sept. 2006, pp. 99–111.

4. “Corrosion Costs and Preventive Strategies in the United States,” Supplement to Materi-als Performance, NACE International, Hous-ton, Tex., July 2002, p. 3.

5. Alawalia, H., “Corrosion Technology Gaps Analysis,” Report Prepared for the NACE Technical and Research Committee (TRAC) and Technical Coordinating Committee (TCC), Presentation at CTW/06, NACE In-ternational, Houston, Tex., 2006.

6. Kane, R. D., others. “Online, Real-Time Cor-rosion Monitoring for Improving Pipeline Integrity — Technology and Experience,” Corrosion/2003, Paper No. 03175, NACE In-ternational, March 2003.

7. Kane, R. D. and Trillo, E., “Evaluation of Multiphase Environments for General and Localized Corrosion,” Corrosion/2004, Paper No. 04656, NACE International, March 2003.

8. Eden D. A. and Srinivasan, S., “Real-time, On-line and On-board: The Use of Computers, Enabling Corrosion Monitoring to Optimize Process Control,” Corrosion/2004, Paper No. 04059, NACE International, March 2004.

9. Kane, R. D. and Campbell, S., “Real-Time Corrosion Monitoring of Steel Influenced by Microbial Activity (SRB) in Simulated Seawa-ter Injection Environments,” Corrosion/2004, Paper No. 04579, NACE International, March 2004.

10. Covino, Jr., B. S., others. “Fireside Corrosion Probes for Fossil Fuel Combustion,” Corro-sion/2006, Paper No. 06472, NACE Interna-tional, March 2006.

11. Eden, D. C. and Kintz, J. D., “Real-time Cor-rosion Monitoring for Improved Process Control: A Real and Timely Alternative to Upgrading of Materials of Construction,” Paper No. 04238, Corrosion/2004, NACE In-ternational, Houston Tex., 2004.

12. Yamamoto, K., “Technical Proposals to Prevent Material Failures And Accidents in Chemical Process Industries”, Corro-sion/2006, Paper No. 06211, NACE Interna

AuthorDr. Russell Kane, an inter-nationally recognized expert in corrosion evaluation and modeling, is the director of corrosion services at Honey-well Process Solutions (14503 Bammel N. Houston Road, Suite 300 Houston, Tex.; Email: russ.kane@honewell.com; Phone: 281-444-2282 X32). Kane received NACE’s A.B. Campbell and Techni-

cal Achievement Awards and ASTM’s Sam Tour Award for distinguished contributions to corro-sion research, development, and evaluation. His doctorate is in metallurgy and materials science from Case Western Reserve University.

Your Right SourceFor Well Engineered

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e-mail at: s a l e s @ d i p e s h e n g g . n e tor log on to: w w w . d i p e s h e n g g . c o m

Conforming to ASME, TEMA, PED, DIN, BS, IS, SMPV,

API etc. Meeting 'C-GMP Standards for Pharma Sector

: S T A I N L E S S S T E E L• • •D U P L E X ST E E L C A R B O N ST E E L A L L O Y S T E E L• • • • •HASTELLOY INCONEL NICKEL MONEL CUPRO-NICKEL• • •T I T A N I U M A L U M I N I U M A L U M I N I U M B R O N Z E

3, Sheroo Villa, 87, J. P. Rd., Near Andheri Sports

Complex, Andheri (W), Mumbai - 400 053, INDIA.

Tel.: 91-22-2674 3719. Fax: 91-22-2674 3507.

Circle 16 on p. 82 or go to adlinks.che.com/6896-16

We also offer Equipment with ASME "U" Stamp from Our sister company M/s Unique Chemoplant Equipment

34-41 CHE 6-07.indd 41 5/25/07 4:34:42 PM