Water & Process Technology, Trends, and Innovations Newsletter
SPRING 2015
Spring Tower Start-Up Tips & Tricks Many cooling towers start-up in the spring and you need your cooling equipment to work reliably during the hot summer months. Unexpected outages are very expensive, and clean heat transfer surfaces contribute directly to your bottom line energy savings. A little effort spent getting your cooling tower ready in the spring will pay big dividends throughout the summer cooling season. Follow these steps to reduce equipment failure, minimize corrosion and prevent the potential for dangerous Legionella bacteria outbreaks. Prior to start-up, physically clean the tower basin. Use shovels, brooms, hoses, or whatever is necessary to remove debris and dirt. Clean out strainers and filters. Lubricate fans and motors, and perform any other annual mechanical maintenance recommended in the equipment manuals. Be sure to remove any excess lubrication – oils and greases can be future food for bacterial growth. Replace sacrificial anodes on chiller heads. Re-passivate both the steel and copper metal cooling surfaces. The metal has been exposed to air and humidity during the off season, and protective coatings are thin or lost entirely. Rebuilding them takes more than the normal chemical maintenance dosage. There are a few ways to achieve the proper results. Option #1: Fill the cooling system. Add U.S. Water’s TowerClean 819 to achieve 1600 ppm as product, and circulate without heat load for 24-48 hours. Either drain and refill, or blowdown heavily as you bring up the heat load and start regular chemical feed. TowerClean 819 is designed to passivate both steel and copper surfaces.
IN THIS ISSUE:
PURSUIT OF A GREEN CORROSION INHIBITOR: PART 2 With environmental regulations tightening, the development of an environmentally-friendly, zero phosphate green corrosion inhibitor is nearing completion. Page 2
REVERSE OSMOSIS MEMBRANE ADVANCEMENTS Option #2: Start the cooling system under low load, and feed double the normal scale and corrosion inhibitor for 72-96 hours. This is not as effective as the TowerClean 819 treatment, so it takes a little longer. However, if your plant operates under an NPDES permit, this may be your best approach. Remove biofilm and kill bacteria. Be especially thorough with stagnant lines or dead legs. While circulating the initial cooling system fill water (with TowerClean or start up chemical dosage) add oxidizing biocide to achieve 0.5-1.0 ppm free residual. Shock the system with 1.5 times normal dose of your non-oxidizing biocide, and add a biodispersant (CWT 405 at 60-100ppm). Check to make sure if you keep reagents and testing solutions on site that they are not past their expiration date. If they are, order new ones. Get coupons on order to have them available for use once a full load has been reached on the towers. Order new Head (KOP) kits for chemical feed pumps coming on line. U.S. Water can help provide quotes for pump kits, repair kits and replacement parts. Contact a team member today.
Page 3
Contrary to popular perception, RO membranes are not “all the same”. Choosing the correct RO membrane for your application can result in less maintenance and operating cost.
UNDERSTANDING THE GLOBAL HARMONIZATION SYSTEM AND WHAT IT MEANS FOR YOU As of June 1, 2015, all chemical manufacturers in the United States must ship their products with GHS compliant labels and SDS’. Page 4
The Pursuit of a Green Carbon Steel Corrosion Inhibitor: Part 2 Matthew LaBrosse, PhD & Donovan Erickson, CWT
Abstract Many inhibitors considered for use in an environmentally friendly corrosion inhibitor program are organic in nature and may be subject to oxidation. This paper aims to expand on previous studies to determine acceptable green corrosion inhibitors for use in open system cooling waters by examining the effect of oxidizing biocide on their performance. Pilot-scale corrosion testing is used to generate results from corrosion coupons and corrator electrodes under chlorinated synthetic water conditions. Several carbon steel corrosion inhibitors are examined and their performance monitored under conditions of continuous chlorination over five days. The results are used to further validate and select the most appropriate and cost effective product for use as a green corrosion inhibitor.
Introduction Organic and inorganic corrosion inhibitors and combinations thereof have been used for many years to reduce corrosion of mild steel in industrial heat exchange equipment. It is important that the inhibitors used for mild
steel corrosion protection be as safe to use as possible and be environmentally friendly. In previous work, the pursuit of a green carbon steel corrosion inhibitor led to examination of several commercially available inhibitors under synthetic laboratory conditions.1 This paper is a continuation of that quest by concentrating on many of these same inhibitors and the effect of oxidizing biocide, such as sodium hypochlorite, on their performance. It is known that oxidation of inhibitors can affect their performance. For instance, reversion of some phosphonates to orthophosphate is quite common under the right oxidation conditions.2 Some manufacturers have suggested that their phosphorous based organic inhibitors be protected with amine to prevent this phenomenon.2 It is thought that combined chlorine (e.g. chloramines) is less destructive of inhibitor structures than free chlorine. Another example of a performance issue for inhibitors is the oxidation of azoles and the resultant increase in yellow metal corrosion if too much azole is lost in the affected system. This can lead to a serious secondary problem of increased mild steel corrosion caused by plating of the copper
onto the mild steel.3 Some water technology providers have recognized this serious problem and used various methods to combat the loss of azole due to oxidizing biocides.4 Oxidizing biocides like sodium hypochlorite are used to reduce biological problems in cooling systems. They also minimize loss of heat transfer and minimize health related issues like Legionella pneumophila. Biological slimes can lead to under-deposit corrosion and efficiency loss due to a combination of organic and inorganic scale deposits.5 Legionella is a serious health concern and has even lead to the death of affected individuals.6 Aside from possible negative health consequences, poor biological control can also be a great liability to facilities and management for unprotected systems. Although oxidizing biocides perform the very necessary function of minimization (continued on page 6)
2
www.uswaterservices.com
Reverse Osmosis Membrane Advancements Every day consumers research and identify what goods and services are available in the market for the particular area they are looking for. They buy based on the features they value and the price they are willing to pay. It’s not very common that a consumer will buy without some level of evaluation. Contrast that with decisions in the industrial world and many times that level of evaluation doesn’t take place. Rather, we often hear generalities like “…all chemicals are the same…” or “…everyone provides service.” These generalities may be due to negotiating tactics or the users’ lack of awareness of the differences between the various goods and services.
In the realm of water treatment, reverse osmosis (RO) membranes are a particular area that is commonly subject to these generalities. This is primarily due to the fact that the original thin-film composite (TFC) membranes generated a few decades ago were generally the same with respect to performance and pricing. Over time the industrial community solidified a perception that “RO membranes are the same.” While that perception and statement may have arguably been true in the past, manufacturers are innovating at a fast pace and the industry is changing due to the characteristics that these new breeds of RO membranes exhibit. Industrial users would benefit approaching the evaluation of RO membranes like they do purchases in their personal life…do some evaluation to understand the features of each. Important considerations need to be taken into account like the feed water characteristics, the mechanical capabilities of the machine and the performance requirements of the downstream users. U.S. Water is both technology and manufacturer agnostic and can evaluate a given application through unbiased glasses. The fact that U.S. Water specializes in not only equipment design but also on-going chemical supply and consulting services, provides us a unique opportunity to partner with our clients to help them understand their options by taking into account all aspects of the process. Just a few years ago the evaluation of RO brackish water membranes was relatively simple and consisted of answering a few questions like:
1. What diameter?
2. How many square feet per membrane?
3. Regular pressure or low-energy?
Most answers were clear and easy based on the capacity requirement and the significant permeate quality differences between regular elements and low-energy versions. (continued on page 11)
www.uswaterservices.com
3
Understanding the Global Harmonization System and What it Means For You By June 1, 2015, all United States chemical manufacturers and importers are required to adopt the Occupational Safety and Health Administration’s (OSHA) new standardized classification and labeling system, The Global Harmonization System (GHS). GHS is an international approach to standardized hazard communication through a single set of hazard ratings, product labels and Safety Data Sheets (SDS). What does this mean for you? A standardized way of classifying and labeling chemicals will improve the safety and health of workers through effective communications that are consistent worldwide, improving the understanding of the hazards to ensure appropriate handling and safe use of workplace chemicals. The GHS standardized approach will include detailed criteria for determining what hazardous effects a chemical poses, as well as standardized label elements assigned by hazard class and category.
4
www.uswaterservices.com
What are the major changes to the Hazard Communication Standard? Right now, a more severe hazard is indicated by a higher hazard rating. This will change with the new GHS. Workers will now need to watch for a lower hazard rating because it is associated with a higher risk, and the higher rating is now less of a risk. Along with the hazard rating, pictograms have been added. The GHS compliant labels and pictogram examples are displayed to the right. When will U.S. Water’s Safety Data Sheets and labels be complaint with the new GHS format? On May 1, 2015 U.S. Water began shipping products with new labels that meet the new standardized GHS criteria; however, during this one month transition, please expect to receive shipments with either the old MSDS’ and labels or the new safety data sheets and labels. Safety Data Sheets can be obtained by contacting U.S. Water Customer Service (1866-663-7633), contacting your U.S. Water Representative, accessing U.S. Water Reports™ or requested through our website, www.uswaterservices.com
GLOBAL HARMONIZATION SYSTEM’S NEW PICTOGRAMS
The LABELS will be updated to include:
The SAFETY DATA SHEET will be updated to include:
Full descriptions can be found at www.osha.gov
1 Hazard pictograms
1 GHS classification for the product
2 Hazard pictograms
Health Hazard
(see table to left)
2 Signal word (i.e. Warning or Danger)
3 Signal word
3 Hazard statements (i.e. “causes serious eye irritation”)
5 Precautionary statements
4 Standardized hazard statements
4 Precautionary statements which includes handling and disposal instructions and safety procedures
NEW FORMAT Flammable
Environmentally Damaging
Corrosive OLD FORMAT
BoilerShield 2186
12270 43rd. St. NE St. Michael, MN 55376 763‐689‐3636
Product of USA
Emergency Phone number: 1‐800‐255‐3924 (Chem‐tel)
Irritant
PRODUCT USE: Boiler Treatment
DIRECTIONS FOR USE: Use only as directed by your US Water Services Technical Service Representative and in accordance with good manufacturing practice. Before using, please read and understand the Material Safety Data Sheet. PRECAUTIONS: Can cause burns to eyes, and skin. Do not get in eyes, on skin or on clothing. Do not taste or swallow. Do not inhale mist. Wash thoroughly after handling. Use with adequate ventilation. For industrial use only. FIRST AID: Eye:
Acute Toxicity
Flush eyes with plenty of running water for at least 15 minutes. Seek medical attention if irritation persists.
Skin:
Flush affected area with plenty of soap and water while removing contaminated clothing. Wash or destroy contaminated garments. Seek medical attention if irritation develops.
Ingestion:
Drink several glasses of water. Do not induce vomiting. Never give fluids to an unconscious person. Seek medical attention.
Inhalation:
Remove from contamination. If person has stopped breathing, give artificial respiration and seek immediate medical attention.
PROTECTIVE EQUIPMENT: Eye: Safety goggles Skin: Protective gloves Other: Eye‐wash station, safety shower Respiratory: Not normally needed if good ventilation is present
HAZARDOUS INGREDIENTS: CAS# Sodium Hydroxide 1310‐73‐2 Diethylaminoethanol 100‐37‐8 HMIS RATING: Health: 1 ‐ Slight Hazard Flammability: 0 ‐ Minimal Hazard Reactivity: 0 ‐ Minimal Hazard PPE B ‐ Goggles, Gloves SHIPPING INFORMATION: Shipping Name: Corrosive Liquids, N.O.S. Contains: Diethylaminoethanol Hazard Class: 8 Packaging Group: PG II Shipping Notations: None EMERGENCY RESPONSE: For Fire: For fires involving this material, do not enter any enclosed or contained fire space without proper protective equipment, such as self‐contained breathing apparatus. For Spill: Prevent material from entering sewers and waterways. Recover as much as possible, then absorb remainder with inert material. See MSDS for further instructions. Dispose of in accordance with Federal, State and Local regulations.
Net wt
LB
KG
Gross wt
LB
KG
LOT #
www.uswaterservices.com
5
The Pursuit of a Green Carbon Steel Corrosion Inhibitor (continued from page 2) of biological problems, they are also known to reduce the efficiency of some scale and corrosion inhibitors as previously mentioned. One of the main purposes of this current research is to identify green inhibitors that are least affected by oxidation. The relationship between inhibitor choice, mild steel corrosion rates, and copper corrosion rates was also investigated in this work.
in previous work.1 This work concentrates on testing the organic inhibitors and their possible reaction with an oxidizing biocide such as sodium hypochlorite. An enhanced phosphonocarboxylate (EPOC) has been added to the list of organic inhibitors investigated in this work while stannous chloride has been omitted from the testing because it is inorganic.
Experimental Procedure
Methodology
“
Moving towards greener alternatives for open recirculation treatments does not necessarily lead to sacrificing inhibitor performance or increasing usage cost.
The conditions of the test were identical to As was the case in previous work, the goal is those found in our previous work, except for the to be as green as possible while performing automatic addition of a bleach solution based corrosive and scaling, shown in Table 1. Later adequately for the purpose intended. In the on an ORP probe. After 24 hours of a test run, tests runs were done using a water that would first paper, green criteria were identified as the ORP set point was increased by 100 mV. The be considered low hardness to simulate a soft high biodegradability, low ecological toxicity, free and total chlorine levels were intentionally water system, shown in Table 2. favorable NPDES status, minimal heavy high at 0.5–1.5 and 1.0–2.5, respectively, to Test Apparatus metals, goodTEST safety APPARATUS profile, and status as a simulate a system that did not have good Figure 1 shows the test apparatus, consisting drinking water additive. Certain inhibitors control, as can of be acommonly found field theofreturn Figure 1 shows the test apparatus, consisting circulation loopinwith waterloop linewith the return water line a circulation were identified to be more favorably green conditions. This also provided circumstances aerated before returning to the sump. This provided the necessary oxygenaerated to simulate beforecooling returning to the sump. This than others,tower including: aspartic were conducive to comparing inhibitors water. The acid flowpolymer rate was that 7.0 gallon per minute in 1” clear PVC piping for ease visual oxygen to simulate provided the of necessary (AAP), phosphono-carboxylic acid mixture to a control. Test runs were five days long inspection. This corresponds to a linear velocity of 3.2 feet per second, which is tower in the water. range The of flow rate was 7.0 cooling (PCM), hydroxyphosphonic acidfor corrosion (HPA), during which mild 7steel copper corrator accepted flow rates coupon racks. The and temperature for eachgallons run was maintained per minute in 1” at clear PVC piping for polyamino-phosphonate (PAP), and stannous data was collected. Appearance of corrosion 95 degrees Fahrenheit; the heat was provided by the circulation pump. Oxidizing biocide was This corresponds to a ease of visual inspection. chloride. Corrosion inhibition of ancoupons was also and observed. of the This tests feature also added to themechanisms sump using ORP monitor relay Most set-point. allowed forfeet per second, which is in linear velocity of 3.2 these inhibitors are discussed in more detail were run using a synthetic water that was both automatic oxidant addition for the five day test runs. the range of accepted flow rates for corrosion
CONTROLLER HOCl
6
ORP RELAY
Figure – Corrosion testing testing circulation loop. Figure 1 –1Corrosion circulation loop.
ORP
pH COND
SUMP
www.uswaterservices.com
RESULTS AND DISCUSSION
CORROSION RACK
coupon racks.7 The temperature for each run was maintained at 95 degrees Fahrenheit; the heat was provided by the circulation pump. Oxidizing biocide was also added to the sump using an ORP monitor and relay set-point. This feature allowed for automatic oxidant addition for the five day test runs.
Results and Discussion HARD WATER Initial testing was performed on synthetic high hardness water. The composition of this water is shown in Table 1. Corrosion Coupons Due to the shortened five day exposure time of each trial, coupon analysis was limited to qualitative observations. The results, shown in Table 3, provide a visual comparison between corrosion inhibitors. Under the test conditions outlined in the experimental procedure, the carbon steel inhibitor performance can be ranked as follows: EPOC ≈ PCM > PAP ≈ HPA/MEA >> AAP Under test conditions, residual orthophosphate and azole levels were measured at the conclusion of each five day test. Results are shown in Table 4. There was little phosphate in the system at the start of each run and any orthophosphate at the end was due to the reversion of organic phosphonate to orthophosphate. The azole level at the beginning of each run was 3 ppm. The reduction of azole is due to its susceptibility to oxidation under higher sustained ORP levels.4 The AAP that was used contained a small amount of phosphate resulting from the manufacturing process. Reversion of an organic phosphate inhibitor to orthophosphate represents a change from an organic program toward an inorganic program, which could affect the overall green status
of the program or its performance. Orthophosphate is not as good at Table 1 – High hardness synthetic water conditions. inhibiting mild steel corrosion as organic phosphate, especially at low levels.8 Item Concentration Unit (ppm) Performance of an orthophosphate Ca 543 CaCO3 program may be reduced due to Mg 140 CaCO3 increased scaling potential of calcium HCO3 328 CaCO3 phosphate, which could introduce C1 114 C1 new mechanisms of corrosion such SO4 505 SO4 as under deposit corrosion.9 This can Polymaleic Acid 8.5 Active be addressed by lowering the pH or Copolymer 8 Active Table 3 shows that both the AAP and control coupons have been plated with increasing the phosphate dispersant Tolyltriazole 3 showsbe that the AAP test has no residual azole after five Active days. This is a stron polymer, however this can often 3 ppm azole in these systems has been degraded by the hypochlorous acid a difficult to control. Table 2 –isLow hardness synthetic water corrosion conditions. azole is depleted, there nothing to protect the copper coupon. T Changes in the ratio of from organic its corrosion readily plates on the surface of the mild steel coupon. Th Item Concentration Unit (ppm) Table 3 do not show this copper plating. It is the belief of the authors that th phosphate to orthophosphate can also Ca 80 CaCO 3 susceptible to oxidation than the other organic inhibitors, which creates a hi introduce system testing errors and Mg Control of hypochlorous 50 acid addition CaCO hypochlorous acid. was 3 based on free control difficulties that can lead to an chlorine. Hence,HCO it is3 possible that the AAP chlorine than the 110 run used more CaCO 3 increase in the total phosphorous in leading to higher chlorides and a faster azole degradation potentially rate. C1 180 C1 the system. More phosphorous in a SO4 60 SO4 water system can lead to increased fish Table 3 – Hard water corrosion coupon results. mortality caused by eutrophication, Table 3 – Inorganic Inhibitor Corrosion Coupon Results algae growth, and loss of oxygen. Dosage Treatment Dosage (ppm Carbon Steel Coupon Carbon Steel Coupo Minimizing the loss of azole in a systemTreatment (ppm Active) Active) is also beneficial to the green status Control – of an inhibitor because azole is knownControl – to increase the aquatic toxicity of an AAP 15 inhibitor.10 For a system that loses 15 azole due to oxidation, more must beAAP fed to maintain yellow metal corrosion HPA/MEA 15/10 protection, possibly increasing theHPA / MEA 15 / 10 overall toxicity of the system water. PAP Although the system containing EPOC PAP shows the least deterioration of azole, the reversion of organic phosphate PCM to orthophosphate was quite high.PCM Conversely, PCM shows minimal EPOC reversion to orthophosphate, but coincides with a high loss of azole in theEPOC
system. HPA/MEA and PAP coincided with less azole deterioration than PCM, but this may be due to the higher ratio of total chlorine to free chlorine provided by the amine functionality of these inhibitor combinations. Even though MEA was added to the HPA to minimize reversion to orthophosphate, the reversion over the five day test period at continuously elevated oxidation levels was substantial.
15 15 15
15
15
15
Table 4 – Orthophosphate and azole residuals after 4 – Orthophosphate and azole residuals after 5 da 5Table day test. Inhibitor
Orthophosphate
Azole
Azole Orthophosphate (ppm TTA) Inhibitor (ppm PO4) (ppm TTA) (ppm PO4) AAP AAP 0.50 0.00 0.50 0.00 HPA/MEA 9.30 0.90 HPA/MEA 9.30 0.90 5.00 0.70 PAP PAP 5.00 0.70 0.25 0.40 PCM PCM 0.25 0.40 EPOC 4.72 1.70 EPOC 4.72 1.70
www.uswaterservices.com
7
Corrator Analysis This type of corrosion analysis yields graphical results that provide a quantitative representation for the full five day test run. The twochannel corrator output provided continuous results on general corrosion and the pitting potential, which is called the imbalance.11 Addition of oxidizing biocide led to large variability in the data sets. Graphical smoothing of the data was performed for ease of comparing the different corrator data sets. Examples of the raw and smoothed data are shown in Figure 2. The raw data shows the copper corrosion spikes corresponding to hypochlorous acid additions. Binary combinations of organic inhibitors were also investigated in this work. In one example, the apparent combinative effect of AAP and PAP was observed. While AAP and PAP performed modestly as individual mild steel corrosion inhibitors over the course of the five day test, Figure 5 shows there is a combined positive effect of having both inhibitors in the system. Table 3 shows each inhibitor, AAP and PAP, was tested at a concentration of 15 ppm as active product. For the combined inhibitor testing, the total treatment concentration was held constant. Hence, AAP and PAP were each added to the system at a concentration of 7.5 ppm as active product. Copper corrosion rates can also be improved when treating with combinations of organic inhibitors. Figure 6 shows the effect of adding both AAP and PAP to the system at a concentration of 7.5 ppm as active product for each inhibitor. The sharp spikes observed at 24 hours are a result of increasing the ORP set point by 100 mV. Each inhibitor starts the test with a corrosion rate below 0.5, but rises to 2.0 by the end of the five day test. The combined inhibitor, however, sustains a
Figure 2 – Graphical smoothing of data
Figure 2 – Graphical smoothing of data.
corrosion rate below 0.5 for the entire duration of the run. It should be noted that each run, including the control, had a background level of 3 ppm tolyltriazole added at the start of the test, as shown in Table 1. As previously discussed, this again shows the susceptibility of azole degradation under oxidizing conditions. SOFT WATER Secondary testing was performed on synthetic low hardness water. The composition of the water is shown in Table 2. The aim of this testing was to compare a traditional soft water open recirculation treatment against a greener option, both of which are shown in Table 5. Both inhibitors programs, as well as the control, were used at a dosage rate of 150 ppm. Hence, the values listed in Table 5 are the active ingredient concentrations in the system at a dosage rate of 150 ppm. The greener option was constructed based on the results from the hard water testing discussed previously. Although there is an increase in the total organic phosphorous of the product, it was thought that the reduction in zinc and removal of molybdate makes the overall product greener than the traditional open recirculation treatment program. Table 5 also shows the traditional treatment program is 40 percent more costly than the greener option, although this was not the Figure 3 – Hard water mild steel corrosion rates for organic inhibitors. goal in developing the greener product. Corrosion Coupons Table 6 shows the mild steel corrosion coupons for the synthetic soft water system. The control coupon for the soft water system does not have the same copper plating shown in the control coupon for the
Figure 3 – Hard water mild steel corrosion rates Figure 3 – Hard water mild steel corrosion rates for organic inhibitors. for organic inhibitors.
Figure 4 – Hard water mild steel imbalance rates formild organic inhibitors. Figure 4 – Hard water steel imbalance rates for organic inhibitors.
Figures 3 and 4 show the organic mildshows steel corrosion and imbalance Figure 2. Theinhibitor raw data the copper corro-rates, respectively, and mild 4 show organic inhibitor mild steel corrosion andcan imbalance rates,when respectively, the syn- of organic Copper corrosion rates also be improved treating withfor combinations FigureFigures 4 – Hard3water steel the imbalance rates for organic inhibitors. for the synthetic hard water system. The corrator results agree well with the corrosion coupon inhibitors. Figurethe 6 shows the effectcoupon of addingobservations, both AAP and PAP to the system at a sion spikes corresponding to hypochlorous acid thetic hard water system. The corrator results agree well with corrosion with EPOC observations, with EPOC showing the best overall corrosion inhibition and PCM showing the concentration of 7.5 ppm as active product for each inhibitor. The sharp spikes observed at 24 additions. PCMareshowing the best imbalance rate. Rankings for the mild best imbalance rate. Rankings for the mild steel corrosion and imbalance rates are as follows:showing the best overall corrosion inhibition andhours a result of increasing the ORP set point by 100 mV. Each inhibitor starts the test with steel corrosion and imbalance rates are as follows: corrosion rate below 0.5, but rises to 2.0 by the end of the five day test. The combined inhibitor Corrosion however, sustains a corrosion rate below 0.5 for the entire duration of the run. It should be note EPOC ≈ PCM > HPA/MEA > PAP > AAP Corrosion: EPOC ≈ PCM > HPA/MEA > PAP > AAP Imbalance PCM > EPOC ≈ PAP >> HPA/MEA ≈ AAP.
Imbalance: PCM > EPOC ≈ PAP >> HPA/MEA ≈ AAP Binary combinations of organic inhibitors were also investigated in this work. In one example, the apparent
Binary combinations of organic inhibitors were also investigated in this work. In one example, combinative effect of AAP and PAP was observed. the apparent combinative effect of AAP and PAP was observed. While AAP and PAP performed modestly as individual mild steel corrosion inhibitors over the course of the five day test, Figure 5 shows there is a combined positive effect of having both inhibitors in the system. Table 3 shows each inhibitor, AAP and PAP, was tested at a concentration of 15 ppm as active product. For the combined inhibitor testing, the total treatment concentration was held constant. Hence, AAP and PAP were each added to the system at a concentration of 7.5 ppm as active product.
8
www.uswaterservices.com
Copper corrosion rates can also be improved when treating with combinations of organic inhibitors. Figure 6 shows the effect of adding both AAP and PAP to the system at a concentration of 7.5 ppm as active product for each inhibitor. The sharp spikes observed at 24 hours are a result of increasing the ORP set point by 100 mV. Each inhibitor starts the test with a corrosion rate below 0.5, but rises to 2.0 by the end of the five day test. The combined inhibitor,
hard water system. This is likely an artifact of the higher amount of hypochlorous acid used in the hard water control test. The higher amount of oxidant deteriorates the azole faster, which leads to higher copper corrosion. The free copper in the system then plates the mild steel corrosion coupon. A lesser amount of continuous chlorination was used in the soft water simulation as the investigation to a greener product choice was narrowed. The free and total chlorine levels during this testing were at 0.25–1.0 and 0.75–1.5, respectively, to simulate a relatively well-controlled cooling water system found in field conditions.
or even combining ingredients in new ways to take advantage of combinative effects. All inhibitors tested provided some level of carbon steel corrosion protection, even under the conditions of high continuous oxidation provided by sodium hypochlorite. Under the experimental conditions, PCM and EPOC performed the best at inhibiting mild steel corrosion as single component inhibitors. There is an apparent combinative effect provided by combinations of certain inhibitors, as was shown for AAP and PAP, particularly in the inhibition of copper corrosion. Copper plating unto mild steel becomes more prevalent as the
Corrator Analysis
Figure 7 shows mild steel corrosion rates under the synthetic soft water conditions for the two different treatments. As before, corrosion rates match up well with qualitative corrosion coupon observations. Figure 8 shows the copper corrosion rates for these inhibitors, which also agrees with the results shown in Figure 7 that the greener treatment performs better than the traditional treatment. Along with Table 6, Figures 7 and 8 demonstrate that moving toward greener alternatives for open recirculation treatments does not necessarily tothe sacrificing inhibitorlevelperformance increasing usage cost. that or each run,atincluding the control, had a background level of 3 ppm tolyltriazole added at the at each run,lead including control, had a background of 3 ppm tolyltriazole added the
Table 6 – Soft water corrosion coupon results.
startthe of the test, as shown in Table 1. As previously discussed, this again shows the susceptibility art of the test, as shown in Table 1. As previously discussed, this again shows susceptibility Treatment of azole degradation under oxidizing conditions. azole degradation under oxidizing conditions.
Dosage (ppm)
Conclusions
Control
A pilot test apparatus is capable of screening potential corrosion inhibitors and combinations of inhibitors to move toward greener products. This may include reducing the concentration of less desirable ingredients, eliminating certain ingredients altogether,
Traditional
150
Greener
150
Figure 5 – Hard water mild steel corrosion rates for combined inhibitors. Figure 5 – Hard water mild steel corrosion rates for combined inhibitors.
Figure 5 – Hard water mild steel corrosion rates for combined inhibitors.
Figure 6 shows the effect of adding both AAP and PAP to the system at a concentration of 7.5 ppm as active product for each inhibitor. The sharp spikes observed at 24 hours are a result of increasing the ORP set point by 100 mV. Each inhibitor starts the test with a corrosion rate below 0.5, but rises to 2.0 by the end of the five day test. The combined inhibitor, however, sustains a corrosion rate below 0.5 for the entire duration of the run.
–
Corrator Analysis Figure 7 shows mild steel corrosion rates under the synthetic soft water conditions for the two different treatments. As before, corrosion rates match up well with qualitative corrosion coupon observations. Figure 8 shows the copper corrosion rates for these inhibitors, which also agrees with the results shown in Figure 7 that the greener treatment performs better than the traditional treatment. Along with Table 6, Figures 7 and 8 demonstrate that moving toward greener alternatives for open recirculation treatments does not necessarily lead to sacrificing inhibitor performance or increasing usage cost. Figure 7 – Soft water
Figure 6 – Hard water copper corrosion rates for combined inhibitors. Figure 6 – Hard water copper corrosion rates for combined inhibitors. Figure 6 – Hard water copper corrosion rates for combined inhibitors.
While AAP and PAP performed modestly as individual mild steel corrosion inhibitors over the course of the five day test, Figure 5 shows there is a combined positive effect of having both inhibitors in the system. Table 3 shows each inhibitor, AAP and PAP, was tested at a concentration of 15 ppm as active product. For the combined inhibitor testing, the total treatment concentration was held constant. Hence, AAP and PAP were each added to the system at a concentration of 7.5 ppm as active product.
Carbon Steel Coupon
mild steel corrosion rates.
Figure 7 – Soft water mild steel corrosion rates.
Figure 7 shows mild steel corrosion rates under the synthetic soft water conditions for the two different treatments. As before, corrosion rates match up well with qualitative corrosion coupon observations.
www.uswaterservices.com
9
Figure 8 – Soft water copper corrosion rates. Figure 8 – Soft water copper corrosion rates.
CONCLUSIONS A pilot test apparatus is capable of screening potential corrosion inhibitors and combinations of inhibitors to moveTable toward greener products. This may include reducingof the concentration of less 5 – Active concentrations soft water desirable ingredients, eliminating certain ingredients altogether, or even combining ingredients in inhibition new ways to takecorrosion advantage of combinative effects. programs. All inhibitors tested provided some level of carbon steel corrosion protection, even under the conditions of high continuous oxidation provided by sodium hypochlorite. Under the experimental conditions, PCM and EPOC Units Traditional performed the bestInhibitor at inhibiting mild steel corrosion as single Control component inhibitors. There is an Greener apparent combinative effect provided by combinations of certain inhibitors, as was shown for (ppm) (ppm) (ppm) (ppm) AAP and PAP, particularly in the inhibition of copper corrosion.
Polymer and
Active
10.0
10.0
Copper plating unto mild steel becomes more prevalent as the concentration of oxidant increases Organic and the level of azole copper inhibitor diminishes. Reducing the oxidation degradation of azole and other inhibitor components is important in seeking greener product offerings because this Phosphate can reduce the total amount of inhibitor used while still maintaining good scale and corrosion protection. This work has shown that under pilot conditions, it is possible to design a greener soft Orthophosphate PO4 or increase 0.00 usage cost.0.00 water make-up product that does not sacrifice performance More work is necessary to further compare pilot results with field trials.
0.02
1.5
Molybdate
6.0
0.0
Mo
Tolyltriazole
0.00 3.0
3.0
3.0
–
–
1.4
1.0
Table 6 – Soft water corrosion coupon results.
Table 6 – Soft water corrosion coupon results. Treatment Treatment Control
Control
Traditional
Traditional
The authors wish to thank the Association of Water Technologies for allowing this paper to be presented and to U.S. Water for the resources necessary to conduct the research.
1.0
Active
Normalized Cost
Acknowledgments
0.0
Total P 0.02 Phosphorous ACKNOWLEDGMENTS
The authors wish to thank the Association of Water Technologies for allowing this paper to be presented and to US Water Services for the resources to conduct the research. Zinc Znnecessary 0.00 2.0
concentration of oxidant increases and the level of azole copper inhibitor diminishes. Reducing the oxidation degradation of azole and other inhibitor components is important in seeking greener product offerings because this can reduce the total amount of inhibitor used while still maintaining good scale and corrosion protection. This work has shown that under pilot conditions, it is possible to design a greener soft water make-up product that does not sacrifice performance or increase usage cost. More work is necessary to further compare pilot results with field trials.
14.8
Greener
Greener
Dosage Dosage (ppm) (ppm)
Carbon Steel Coupon Carbon Steel Coupon
–
–
150
150
150
150
Corrator Analysis Figure 7 shows mild steel corrosion rates under the synthetic soft water cond different treatments. As before, corrosion rates match up well with qualitative REFERENCES [6] B.J. Marston, H.B. Lipman, and R.F. Breiman, “Surveillance for Legionnaires’ Disease: Risk Facobservations. Figure 8 shows theofcopper corrosion rates for(1994). these inhibitors, w tors for Morbidity and Mortality”, Archives Internal Medicine, 154, 2417-2422 [1] M. LaBrosse and D. Erickson, “The Pursuit of a Green Carbon Steel Corrosion Inhibitor”, The with the results shown in Figure 7 that the greener treatment performs better Analyst Technology Supplement, Fall (2012). [7] B.P. Boffardi, “Corrosion and Fouling Monitoring of Water Systems”, The Analyst Technology Supplement, Spring (2010). treatment. Along with Table 6, Figures 7 and 8 demonstrate that moving tow [2] Association of Water Technologies Technical Reference and Training Manual, 2nd ed, chapter 4, section 5.10.6 (2009). [8] Association of Water Technical Reference anddoes Training Manual, 2nd ed, chapter 4, to sac alternatives for openTechnologies recirculation treatments not necessarily lead section 5.10.1 (2009). [3] H. Van Droffelear and J.T.N. Atkinson, Corrosion and its Control: An Introduction to the Subject, performance or increasing usage cost. 2nd ed., chapter 2, page 25-26 (1995).
[4] K.M. Given, R.C. May, and C.C. Pierce, “A New Halogen Resistant Azole (HRA) for Copper Corrosion Inhibition”, Conference on Industrial Water, Paper IWC-98-60 (1990). [5] H. Van Droffelear and J.T.N. Atkinson, Corrosion and its Control: An Introduction to the Subject, 2nd ed., chapter 6, page 98-100 (1995).
10
www.uswaterservices.com
[9] H. Van Droffelear and J.T.N. Atkinson, Corrosion and its Control: An Introduction to the Subject, 2nd ed., chapter 2, page 33-35 (1995).
[10] D.L. Hjeresen, “Green Chemistry and the Global Water Crisis”, Pure and Applied Chemistry, 73, Figure 7 – Soft water mild steel corrosion rates. 1237-1241 (2001). [11] Rohrback Cosasco Systems, Inc., “Model 9020 &9020-OEM Corrater Transmitter User Manual”, November (2004).
Reverse Osmosis Membrane Advancements (continued from page 3)
Fouling Resistant The issue of water conservation is becoming more important and people and businesses are talking about it more regularly. Successful companies that understand the importance of sustainability are acting on this issue and looking at ways to reuse water or utilize impaired water as make-up to industrial processes. As a result, water treatment companies like U.S. Water are continuously challenged with designing mechanical and chemical treatment strategies and processes to deal with these challenging applications. Many times RO technology is part of the solution and as a result the RO membranes can be subject to challenging conditions that might have higher fouling or bioactivity characteristics. Fouling resistant membranes help prolong the run-time of an RO machine by helping prevent accumulation of foulants on the surface of the RO membranes, which results in the need for frequent membrane cleaning. Customers can see the benefit in prolonged membrane life, less operator time, less CIP waste/ cost and increased up-time availability.
membranes feeding the unit. Newer RO membranes The fact that U.S. Water specializes are capable of achieving a higher level of salt rejection, in not only equipment design but which translates to less also on-going chemical supply and maintenance and operating consulting services, provides us a costs associated with the unique opportunity to partner with downstream unit operations. In addition, organizations like our clients to help them understand EPRI in the power industry, their options by taking into account have lowered recommended all aspects of the process. limits like silica and can make it difficult for certain legacy water treatment systems Recent advancements are narrowing the gap to achieve those levels. Having the ability in the differences in rejection and in many to attain greater salt rejection helps users cases we are seeing nearly identical salt achieve newer processing limitations. rejection performance of older “traditional” membranes versus the newer low energy, high rejection elements. The benefit is Low Energy, High Rejection obviously the reduced operating costs “Low Energy” elements have been around associated with pumping pressure. In new for some time; however, their use was applications, the machines can be designed traditionally limited to applications that with these new membrane characteristics could tolerate a fair amount of salt passage. (continued on page 12)
Extra High Rejection Historically high purity water was produced using ion exchange processes like mixedbed demineralizers. When RO systems came along they proved beneficial in pretreating the water to help reduce the operational costs associated with regenerating the resins. In addition electrodeionization (EDI) has become a more industry accepted treatment step and providing EDIs with better feedwater quality enables better product water and less energy. The feedwater to an EDI is a function of the salt rejection of the RO www.uswaterservices.com 11
FOLLOW US ONLINE For more tips, tricks and technical information, visit us at
12270 43rd Street NE St. Michael, MN 55376
www.uswaterservices.com and click on the “FOLLOW US ONLINE” tab to the right to subscribe to our e-newsletter, blog, and LinkedIn!
STAY TUNED! Case Study: “Non-Phosphorus Cooling Tower Treatment, PhosZero™, Provides Advanced Corrosion Protection” in the next issue!
Reverse Osmosis Membrane Advancements (continued from page 11)
used as the design basis, which affords a manufacturer like U.S. Water to reduce the capital costs of the machine and still get equivalent performance. The issues surrounding water are becoming more complicated by the day and the myriad of options available to tackle these challenges continues to grow. Industry users are encouraged to resist the temptation to generalize. Companies should either develop in-house capabilities and skill sets to keep abreast of this changing industry or partner with a solutions company that can help evaluate the options based on what’s available in the industry.
12
www.uswaterservices.com
