Cost analysis of pipes for application in wage systems
Shahram MortezaNia ⇑,Faridah Othman
Civil Engineering Department,Faculty of Engineering,University of Malaya,50603Kuala Lumpur,Malaysia
a r t i c l e i n f o Article history:
Received 13July 2010Accepted 20January 2011
哪吒头
Available online 16March 2011Keywords:I.Corrosion
H.Selection for cost C.Surface treatment
a b s t r a c t
The work described in this study is a preliminary effort to identify the most cost effective pipe material for application in wage collection networks.Firstly,cylindrical concretes coated by epoxy (Ep),polyure-thane (PU),and combination of epoxy and sodium silicate (Ep–SS)were tested to investigate coatings ability to protect concrete samples against corrosion.Secondly,the price of the cured concrete (CC)pipe by designed coatings was compared to that of a new concrete network.Economic analysis was then carried out to compare the prices of the CC and double wall corrugated high-density polyethylene (DWC-HDPE)pipes.The outcomes revealed that the designed coating materials were able to lengthen the concrete pipes rvice life.They acted as a barrier against the aggressive environment,and were able to reduce the corrosion rate in the piping system.By using the designed coatings,it was at least 1.5times more economical compared to replacing it with new pipes.The CC pipes have been found to be more cost effective than DWC-HDPE pipes for pipes diameter larger than 600mm.A computer program was pro-vided bad on the
developed mathematical models which could aid engineers in nominating the proper pipe for optimum cost saving and performance.
Ó2011Elvier Ltd.All rights rerved.
1.Introduction
Concrete,asbestos,iron,plastic,etc.pipe materials are being ud for wer networks.Due to its compatibility with the environ-ment,huge material resources,cost effectiveness,more resistive and strength,concrete has been the most widely construction material [1]ud in wers,treatment plants,and open channels.However,concrete suffers from deterioration and rapid degrada-tion of concrete structures has been reported in wastewater facil-ities.This degradation is due to the acidic environments mostly generated by bacterial activities [2].
Abrasion-resistant interior to withstand scouring action of wastewater carrying gritty materials,durability for long life,ade-quate strength to resist failure or deformation under loads,and impervious walls to prevent leakage are physical characteristics esntial for wer pipes.Besides,resistance of pipe material to chemical attacks (sion)is important enough to be consid-ered in lecting the proper pipe material.Fig.1a shows an exam-ple of load deformation,w
hile Fig.1b demonstrates the corrosion attack captured by a CCTV placed in a wage network in Malaysia.Corrosion deterioration has long-term effect on environment,economy,and society [3,4].The evaluation of current and future
corrosion damage of concrete pipes in wer networks during their rvice life has become imperative for engineers which results as aging decrement of the network.Thus,shortens their remaining rvice life,requires funding for repair or replacement.Due to the high cost and the difficulty of repairing the deteriorated parts,it is required that the material should be long lasting [5].Hence,economical and effective techniques are needed to prevent or con-trol corrosion deteriorations in particular areas of wers espe-cially where H 2S generation is common.The rate of hydrogen sulfide generation in wers depends on wage parameters such as pH,temperature,and turbulence,and so forth [6].Over the time (usually,about 5–30years),dissolved sulfates in water penetrates the hardened concrete and caus deterioration [7].The cracks initiated at the concrete surface by chemical reaction of sulfates,propagate into the concrete core which lead to an increa in diffusivity,permeability,and porosity of concrete structure [1,8,9].Control technologies that can be ud to overcome this is-sue include using acid resistant materials,using chemical or bio-logical treatments,and optimizing the wer hydraulic design [1,4,10].
To protect concrete structures from physical,chemical,or bio-logical degradation and increa their durability,high performance protective surface coating materials can be ud.The coatings can stay in contact with concrete and provide long-term effective pro-tection under vere condition with low maintenance costs [11,12].Sulfuric acid is one of the main substances produced in corrosion process.In order to predict the rvice life of CC
0261-3069/$-e front matter Ó2011Elvier Ltd.All rights rerved.doi:10.1016/j.matdes.2011.01.062
⇑Corresponding author.Tel.:+60173851565;fax:+6079675318.
E-mail address: ,sh7690@siswa. (S.MortezaNia).
structures,it is important to determine the value of sulfuric acid absorption into the CC.Previous rearchers have worked on the quality of organic coating hlorinated rubbers, acrylic,polymer,epoxy,and polyurethane)to protect the concrete surface against corrosion[12–15].They ud cubic and cylindrical concrete samples coated by coating materials to conduct lab exper-iments using accelerated test.Visual inspection,weight changes, etc.,were employed to investigate the coating deteriorations.Their results pointed out that Ep and PU materials provide bett
er perfor-mance,less absorption rate,and more resistance to corrosion.
Sodium silicate(SS)as an inorganic coating material is very u-ful material that can improve the concrete surface properties such as abrasion resistance,chemical durability,hardness,and perme-ability[16,17].In addition,it is reported that silicates form as a gel is similar to the form of alkali silicate reactions whichfills the concrete pores(pore blocking)by swelling.When applied to well-cured concrete that is dry and absorptive,silicate solution will provide reduced dusting and improved density of the concrete sur-face which can decrea the permeability of concrete[16,17].
DWC-HDPE pipe in contrast,has become a popular alternative nowadays becau it is chemically resistive,durable,easy to han-dle,andflexible.It also entails low piping cost,and offers an acceptable rvice life.As an important part of wer construction costs,initial price of pipes is another considerable category in lecting the type of pipe material for u in wer network. Undoubtedly,due tofluctuating prices of DWC-HDPE pipe,lect-ing the type of pipe material is always a challenge task.
This study focud onfinding a cost effective pipe materials to be ud in a wer system.In doing so,objectives can be summa-rized as follows:(i)to investigate the efficiency of coating materi-als on c
oncrete samples which can withstand the aggressive environment,(ii)to calculate the cost of coatings bad on their ability to extend concrete rvice life,(iii)to compare the price of CC and DWC-HDPE pipes in various diameters.In addition,a computer program according to the developed mathematical mod-els was provided to assist municipals in lecting a proper pipe bad on desired variables.
2.Materials and methods
2.1.Materials
The cylindrical concrete samples which reprent the concrete pipe with a water per cement(w/c)ratio of0.36[18],cement con-tent of350kg/m3,Portland cement type V,were ud to conduct tests under laboratory condition.The cylindrical concrete is 10cm in diameter and20cm in height.
Two types of organic coating materials and one inorganic coat-ing material were lected as follows:
(1)Ep(NP Solvent Coating industrial supply,grey color,
q=1.5g/cm3,US$16/kg,ratio of wet/dry weight(Vs)=1.06).
(2)PU(NP Solvent Coating industrial supply,white color,
q=1.35g/cm3,US$27/kg,Vs=1.07).
(3)Ep–SS(SS:R&M chemicals,gel form,70%,q=1.13g/cm3,
US$12/kg,Vs=1.04).
诗经郑风风雨2.2.Methods
Before the coating was applied,the concrete surface preparation was conducted according to ASTM C811-98standard[19]using water pressure and wire brusher to remove any sort of dirt.Ep and PU were applied(100l m thickness)on concrete samples with utmost care to cover all surfaces thoroughly without any defect fol-lowing the supplier recommendations and left in the lab tempera-ture to be completely dry.
The accelerated method,identified as a rapid test[20],is one of the most widely ud tests to investigate the chemical resistance of CC.This method can be performed in two ways[21];i.e.using specimens with large surface area per volume ratio or increasing the aggressive sulfuric acid)concentration.Monteny et al.[21]propod to keep the pH of the solution at a certain level (by titration)for accelerated method using sulfuric acid.In addi-tion,the worst condition in the wer syste
瘦肚腩
ms is due to sulfuric acid produced by bacteria when the pH reaches the value of less than one,which is approximately similar to the concentration of 1–3%sulfuric acid solution[22].
炸扣肉The CC samples were then weighed(W p)by a digital balance having a precision of±0.001.The samples were placed in clod containers(half immersion)filled by2%and10%sulfuric acid solu-tion.During the test,the pH of solution was monitored using the Thermo Electron Corporation3-star portable pH meter to provide a constant condition.The high power magnifying glass30x LED lighted was also ud to visually inspect the samples for the corro-sion signs(coating failure blistering,cracking,orflaking [23]).The failures were picked as indicator to evaluate the experi-mental results to determine the rvice life of designed coatings. The time offirst failure on coated samples immerd in10%sulfu-ric acid solution was recorded.
The time taken for a CC to fail after corrosion initiation is related to the thickness of coating material(L t),the liquid absorption by coating,and the contact time with the liquid.After the designed test period(30-day),samples were taken out of the containers, washed by water,and the damaged parts were removed.According to Lin and Vipulanantan[20],the estimation of the weight changes of the CC structure expod to aggressive environment is a signif-icant parameter to predict the rvice life of coating material. When the samples were completely dry,the samples were
then Deformation of DWC-HDPE pipe under external loads,and(b)corrosion of concrete pipe under chemical attack(cas in wage
weighed(W s).The weight loss percentage(W L)was then calculated using the following;
W L¼ðW pÀW sÞ=W pÂ100ð1ÞThe experiments were repeated for at least three times and the average of measured parameters were obtained.A standard error of5%was employed throughout the exerci.
Generally,the liquid penetrates through the coatingfilm into the concrete when the CC specimens come in contact with liquids. The solutions penetration into coatingfilms can affect concrete structure in two ways.Thefirst way occurs when the solutions do not react with coating materials such as water penetration.In this ca,the rate of water absorption to coatingfilm,for instance, is related to the weight gain by coatingfilm.On the other hand,the cond way happens when the solutions react with the concrete (e.g.sulfuric acid solution)and damage it.Subquently,the con-crete structure will be corroded layer by layer starting from the interface of the coating and the concrete substrate.Hence,the rate of acid consumption by coatedfilm is related to the time coating material is in contact with aggressive environment and the weight loss by coatedfilm[15].The longer the time offirst failure on the coating surface,the less the weight loss[24].The accurate predic-tion of coatings rvice life under corrosion process should be investigated for a long time in the natural environment.Eq.(2)is propod for organic coating materials rvice life prediction bad on their thickness by Murray[24]and Sharifi[25].Here,t is the time that coating can withstand in aggressive environment or the time offirst failure obrvation.
t2¼ðL t2=L t1Þ2Ât1ð2Þwhere L t2and L t1(=100l m in this work)prent the thickness of coating materials,t2is the time offirst failure on the coatingfilm using L t2thickness,and t1is the time offirst failure obrved in 2%sulfuric acid solution.
The relationship between the weight loss(W L)by coated sample immersing in sulfuric acid solution(10–2%)and time offirst failure is given by the following equation:
Z¼W L10%=W L2%¼C t2%=C t10%ð3Þwhere the W L10%and W L2%are the weight loss percentage of sam-ples in10%and2%sulfuric acid solutions,and C t10%and C t2%prent the time offirst coating failure expod to designed solutions.Here, C t2%is equal to t1in Eq.(2).
For Ep–SS,the concentration of sodium silicate was designed by 10%.This reported concentration is enough to make concrete30% resistant to sulfuric acid[25].To estimate the maximum rvice life(t1)for Ep–SS coating material,another test was conducted to compare the efficiency of using Ep–SS and Ep individually(300 and600l m thickness)using10%sulfuric acid solution following the above procedure.The Ep–SS was applied parately on the samples by2layers.After the test period(30days),the calculated weight loss percentage of samples was carried out to estimate the maximum rvice life(t1)for Ep–SS coating material.
The cost of coating materials(P co(US$))was determined for 100cm length of concrete pipe bad on their obtained effective thickness by Eq.(4)and compared to new concrete network cost for the desired rvice life of25years.
P co¼ððA pÂL tÞÂq MÂVsÞÂð1þw=100ÞÂP Mð4Þwhere A p(cm2)is the area of coating on concrete surface (=pÂd pÂL p),d p(cm)prents the internal pipe diameter,L p(cm)
is the length of pipe(100cm in this work),L t(cm)is the coating thickness,q M(g/cm3)prents the density of coating material,w (%)is the wasting percentage;the wasting percentage(w)of PU coating during a coating application was determined as5%followed by Ep coating as6%and SS as10%,and P M(US$/g)prents the coating material price in the Malaysian market.
The total price(TP Cp)of the CC pipe,which includes the initial pipe price(FP Cp)and P co,was then determined,and compared to the price of the DWC-HDPE pipe(P PEp).
TP Cp¼FP CpÂL P=100þP coð5ÞThe comparison was performed for various available pipe diam-eters in the market.In this ca,the rvice life was designed by 50years for data analys.Finally,mathematical models were developed bad on the results and a computer program was provided using Visual C+software which could assist in lecting the proper pipe for optimum cost saving and performance.
3.Results and discussion
3.1.Prediction of extended concrete pipe rvice life using coating materials
The experimental results of the designed organic coating mate-rials are shown in Table1.It can be en from the table that the time offirst failure for Ep coated sample immersing in10%sulfuric acid solution is approximately131h of exposure,while by PU as 159h.Using Eq.(3)and the results,the time offirst failure (C t2%)or the maximum rvice life(t1)for coated samples immerd in2%sulfuric acid can be determined.The maximum rvice life or time(t1)for Ep coating material to resists2%sulfuric acid solution was determined at approximately946h,while for PU it was slightly higher at1282h.The rvice life value for Ep ems to be reasonable as it is less than the maximum rvice life of 1680h as reported by Sharifi[25]for Ep CC with100l m thickness immerd in1%sulfuric acid solution.
Experimental work was performed to estimate the maximum rvice life(t1)for Ep–SS.The results show that the weight loss percentage of sample coated by Ep–SS was 1.21%while;this amount for the sample coated by Ep individually was1.73%using 600l m thickness.Hence,coated sample by Ep–SS was approxi-mately30%more resistant than that coated by Ep individually. Similar result was calculated for coated samples using300l m thickness and the percentages of weight loss for Ep–SS and Ep were 1.42%and2.03%respectively.The efficiency of SS to prolong the resistance of concrete against sulfuric acid solution is also reported by Sharifi[25]as30%.Thus,the maximum rvice life(t1)for Ep–SS coating can be estimated at approximately1229h.
Using Eq.(2)and the above data,the designed coating materials rvice life by various coating thickness can be calculated and the results are illustrated in Fig.2.It can be concluded from thefig-ure that to resist concrete surface in aggressive environment or to delay concrete deterioration by25years,the effective thickness of Ep,PU,and Ep–SS coatings are approximately1500l m, 1300l m,and1350l m respectively.
3.2.Price comparison of designed coatings and new concrete network
Increasing the rvice life of concrete structures under vere conditions is important[26],and it has been shown above that
歪脑袋木头桩故事Table1
Experimental results for Ep and PU coatings immerd
in10%and2%sulfuric acid solution(100l thickness).
Parameters Ep PU
W L10%0.1300.121
W L2%0.0180.015
Z7.228.06
C t10%131h159h
358S.MortezaNia,F.Othman/Materials and Design33(2012)356–361
the designed coatings can lengthen the concrete pipes rvice life
in aggressive environment.The prices of the coating materials (P co)have been calculated using Eq.(4)for various pipes diameter available in the Malaysian market.It was then compared to the prices of new concrete network for similar diameters.For calcula-tion purpos,a25-year designed rvice life has been lected. Fig.3shows the prices comparison of coating materials prices (P co)and the new concrete network for various pipe diameters.
It can be en from Fig.3that the designed coatings with rele-vant effective thickness is more economical compared to replacing the network with new concrete pipes for the designed rvice life of25years.Thefigure depicts that the replacement of new con-crete pipes in the wer network a minimum of 1.5times)more than curing the concrete pipes by designed coat-ings.Thefigur
e also demonstrates that the cost of coating by PU is slightly more expensive compared to tho of Ep and Ep–SS.Only small differences of costing can be en between Ep and Ep–SS. 3.3.Comparison of CC and DWC-HDPE pipe prices
To lect proper pipe materials for a wer system,it is esntial to provide a desired level of rvice life at a minimum cost.One of the major and most costly problems in wer networks and treat-ment plants is the replacement of such system,especially in warm prices for DWC-HDPE and CC pipes for pipes diameter below 600mm.In this ca,the maximum price of DWC-HDPE pipe is roughly US$99/m for525mm,while for CC pipe the Ep coating price is approximately US$101/m,PU coating is US$107/m,and Ep–SS is US$100/m.In addition,for600mm pipe diameter,the maximum price of DWC-HDPE is US$125/m;while for CC pipe using designed PU,Ep,and Ep SS,are US$123/m, US$118/m,and US$113/m respectively.The price of DWC-HDPE is approximately10%more than concrete pipe price coated by designed coating materials.Apgar et al.[27]and Stewart[28]sug-gested the u of corrosion resistance pipe materials which can possibly influence the rate of H2S gas.HDPE pipe as a corrosion resistant material for wer pipes was recommended.Moreover, Nieln et al.[29]indicated that the plastic surfaces are inert and acid will not be neutralized as well as concrete pipes.Due to better performance of DWC-HDPE sist
ance to corrosion,low piping cost,and easy handling,the DWC-HDPE pipe is recom-mended for wer networks below750mm in diameter.
For pipes diameter larger than600mm the price differences be-tween the DWC-HDPE and CC pipes increas,and it ris sharply for pipe diameter larger than900mm.The price of DWC-HDPE pipe for750mm is US$216/m,whereas this amount for CC pipe coated with Ep is US$145/m,with PU is US$155/m,and with Ep–SS is US$139/m.In terms of percentage,CC pipes coated with Ep,PU,and Ep–SS are49%,40%and55%respectively more cost effective than DWC-HDPE pipe.
Thus,it can be concluded that bad on the investigations and economic analysis in this work,the u of DWC-HDPE pipe as a corrosion resistance material is preferred for smaller pipe diameter (i.e.less than750mm),while for larger diameter the CC pipes are recommended for application in the wer networks.In addition, Lahav et al.[30]recommended that small diameter wer pipes are almost made of plastic materials whereas the larger diameter lines(>800mm)are normally made of concrete.
Since lecting a proper pipe for u in a wage network is quite a challenging task,a mathematical model which could aid engineers and decision makers in making an economical compari-son of diffe
rent diameters of CC and DWC-HDPE pipes has been developed.In designing the mathematical model,the Ep–SS coat-ing has been eliminated since it would add more complexity to the model.This complexity is due to using two different types of coatings which may cau some bias in the mathematical model. Furthermore,as it can be en from Fig.3,there is only a slight dif-ference in the cost of coating for Ep and Ep–SS.Bad on outcomes revealed from this work,a mathematical model was designed for lecting a proper pipe for optimum cost saving and performance. To achieve this matter,estimated ratio of DWC-HDPE pipe price and its rvice life(P PEp/SL PEp)should be compared with the results
Fig.2.The rvice life of coating materials vs thickness.
3.Comparison of coating materials with effective thickness and new concrete network bad on designed rvice life of25years(costs bad on IWK(Malaysia), 2008).
4.Cost of CC pipe coated by designed coatings and DWC-HDPE pipe available pipe diameters for the desired rvice life of50years(initial pipes price bad on data of IWK and ResinTech Plastics(Malaysia),2008).
achieved by variables X(model(i)for Ep coating material u)and Y(model(ii)for PU coating material u
).
X¼ðFP CpÂL P=100þðp d p L p L tÞÂðq Ep Vsð1þw=100ÞÞÂP EpÞÂð1=ðSL Cpþ10:797L2
t
Àð6expÀ14ÞL tÞÞðiÞY¼ðFP CpÂL P=100þðp d p L p L tÞÂðq PU Vsð1þw=100ÞÞÂP PUÞ
Âð1=ðSL Cpþ14:63L2
t
Àð2expÀ13ÞL tÞÞðiiÞ
where SL Cp is the rvice life of concrete pipe and P Ep and P PU are the price of Ep and PU coating materials,respectively.Other variables are prented previously.
A computer program was designed bad on the mathematical models above and an example of the screenshot of the software is illustrated in Fig.5.It shows the result of cost comparison between CC coated by Ep and DWC-HDPE pipe(525mm in diameter).The software reported herein can assist municipalities in nominating economical pipe for wer networks u.
4.Conclusions
Chemical tests and economic analysis were carried out to iden-tify the cost effective pipes for u in wage networks.The Ep,PU, and Ep–SS coating materials have fulfilled their function to with-stand the aggressive environment and increa the concrete rvice life.The results pointed out that although the designed coating materials exceed the initial price of concrete pipe but it is more economical compared to replacing with new concrete pipes bad on designed rvice life of25years.Moreover,it was concluded that the u of DWC-HDPE pipe as a corrosion resistance material is preferred for smaller pipe less than 750mm);while for larger diameter the CC pipes are recommended for a designed rvice life of50years.In addition,a computer pro-gram was designed according to the developed mathematical mod-els to assist in lecting the cost effective pipes for u in wer networks.Acknowledgement
The authors gratefully acknowledge thefinancial support by the University of Malaya and the cooperation by Indah Water Konsortium(IWK)to carry out this rearch Project.
References
[1]Abdelkader SM,Pozo ER,Terrades AM.Evolution of microstructure and
mechanical behavior of concretes utilized in marine environments.Mater Des 2010;31:3412–8.
[2]Yamanaka T,Aso I,Togashi S,Tanigawa M,Shoji K,Watanabe T,et al.Corrosion
by bacterial of concrete in werage systems and inhibitory effects of formats on their growth.Water Res2002;36:2636–42.
[3]Zhang L,De Schryver P,De Gusme B,De Muynck W,Boon N,Verstraete W.
Chemical and biological technologies for hydrogen sulfide emission control in wer systems:a review.Water Res2008;42:1–12.
[4]US EPA.Characterization of building-related construction and demolition
debris in the United States.Rep.EPA530-R-98-010.Washington(DC);Office of Solid Waste;1998.
[5]Guermazi N,Elleuch K,Ayedi HF.The effect of time and aging temperature on
structural and mechanical properties of pipeline coating.Mater Des 2009;30:2006–10.
[6]Yongsiri C,Vollertn J,Hvitved-Jacobn T.Influence of wastewater
constituents on hydrogen sulfide emission in wer networks.Environ Eng 2005;131:1676–83.
阜阳生态园[7]Portland cement association.Concrete information:types and caus of
concrete deterioration.PCA R&D Serial No.2617;2002.
[8]Mehta PK,Monteiro PJM.Concrete microstructure,properties and
materials.McGraw-Hill;2006.
[9]Tixier R.Microstructural development and sulfate attack modeling in blended
cement-bad materials.PhD thesis.Arizona:Arizona State University;2000.
[10]De Beliea N,Monteny J,Beeldens A,Vincke E,Van Gemert D,Verstraete W.
Experimental rearch and prediction of the effect of chemical and biogenic sulfuric acid on different types of commercially produced concrete wer pipes.Cem Concr Res2004;34:2223–36.
[11]Vipulanandan C,Liu J.Performance of polyurethane coated concrete in wer
environment.Cem Concr Res2005;35:1754–63.
[12]Almusallam AA,Faiz MKH,Dulaijan SU,Al Amoudi OSB.Effectiveness of
surface coatings in improving concrete durability.Cem Concr Compos 2003;25:473–81.
[13]Shon MY,Kwon H.Comparison of surface modification with amino terminated
polydimethylsiloxane and amino branched polydimethyl siloxane on the corrosion protection of epoxy coating.Corros Sci2009;51:650–7.
[14]Chattopadhyay DK,Raju KVSN.Structural engineering of polyurethane coating
for high performance applications.Polym Sci2007;32:352–418.
[15]Liu J.Performance of coatings in wastewater systems and verification with
analytical models.PhD thesis.Houston-USA:University of Houston;
2000. Fig.5.Example of the computer software screenshot.
[16]Crisman J.The u of silicate solution to cure concrete.March2008.
</fileshare/WhatsNew/silicates.pdf>;2007.
[17]Thompson JL,Silsbee MR,Gill PM,Scheetz BE.Characterization of silicate
alers on concrete.Cem Concr Compos1997;27:1561–7.
[18]ACI.Building code requirements for structural concrete.Farmington Hills(MI):
American Concrete Institute Committee318R-05;2005.
[19]ASTM.Standard practice for surface preparation of concrete for application of
chemical-resistant resin monolithic surfacing,C811-98.American Society for Testing and Materials;2008.
[20]Liu J,Vipulanandan C.Testing epoxy coatings for dry and wet concrete
幸福的歌
wastewater facilities.Protect Coat Linings1999;16:26–37.
[21]Monteny J,Vincke E,Beeldens A,De Belie N,Taerwe L,Van Gemert,et al.
Chemical,microbiological,and in-situ test methods for biogenic sulfuric acid corrosion of concrete.Cem Concr Res2000;30:623–34.
[22]Islander RL,Devinny JS,Mansfield F,Postyn A,Shih H.Microbial ecology of
crown corrosion in wers.Environ Eng1991;117:751–70.
[23]ISO.International organization for standardization part1:introduction general
and designation system.ISO4628-6.Switzerland,Geneva;2003.[24]Murray JN.Evaluation of thick cast polyurethane coatings on steel using EIS
and DC electrochemical techniques.In:Scantlebury D,Kendig M editor.The symposium on advances in corrosion protection by organic coatings.
Pennington(NJ):The Electrochemical Society;1995.
[25]SharifiM.Biological corrosion reduction of concrete wer pipes by organic
coatings.PhD thesis.Iran:Tarbiyat Modarres University;1996.
[26]Chalee W,Ausapanit P,Jaturapitakkul C.Utilization offly ash concrete in
marine environment for long term design life analysis.Mater Des 2010;31:1242–9.
什么是排畸检查
[27]Apgar D,Witherspoon J.Minimization of odors and corrosion in collection
systems:Pha I,Rep.04-CTS-1.Water Environ Res Found.Alexandria(VA);2007.
[28]Stewart R.Plastic pipe–corrosion resistance:ca study of installation
stimulate demand for plastic pipe.Plast Eng2005;61:14–21.
[29]Nieln AH,Vollertn J,Jenn HS,Andern TW,Hvitved-Jacobn T.
Influence of pipe material and surfaces on sulfide related odor and corrosion in wers.Water Res2008;42:4206–14.
[30]Lahav O,Lu Y,Shavit U,Loewenthal RE.Modeling hydrogen sulfide emission
rates in gravity wage collection systems.Environ Eng2004;130:1382–9.
S.MortezaNia,F.Othman/Materials and Design33(2012)356–361361
