matls 4d03 case study #2

MATLS 4D04

Corrosion Case Study #2

Paper Machine Suction Roll & Couch Roll Corrosion

December 12th, 2016

Jianhui Li 1315768

Ran Liao 1315216

Yilin Teng 1317368

Jingming Wang 1307484

MATLS 4D03 Case Study #2

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Contents 1.0 Introduction and Background ............................................................................................................ 2

1.1 Pulp and Paper Industry ................................................................................................................ 2

1.2 Paper Machine Component (suction roll and couch roll) .............................................................. 3

1.3 Paper-machine White Water .......................................................................................................... 4

2.0 Problem Statement ............................................................................................................................ 5

2.1 Composition of Material ............................................................................................................... 5

2.2 Corrosion Mode ............................................................................................................................ 6

2.3 Critical Factors and Mechanism.................................................................................................... 6

3.0 Solution for Corrosion Control ....................................................................................................... 13

3.1 Material Selection ....................................................................................................................... 13

3.2 Environment Control ................................................................................................................... 17

3.3 Technological Control ................................................................................................................. 19

4.0 Failure Prevention ........................................................................................................................... 20

Reference .............................................................................................................................................. 22


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1.0 Introduction and Background

1.1 Pulp and Paper Industry

The pulp and paper industry consists of the industries which manufacturing varieties

of woody plant material into any types of pulp, paper and paperboard. It is one of the

largest industrial sectors in the world because it covers a wide range of paper products,

from catalog paper to tissue [1].

In Canada, pulp and paper industry first began in the 19th century, but the trend of

moving newsprint to electronic media makes some depression in this industry recently.

However, pulp and paper industry is still one of the fundamental industries in the

Canadian economy, especially in the northern part of Canada [1].

Pulp and paper industry mainly has 6 stages. First of all, the trees are harvested and

cut into logs, then the logs are transported to the mill and using the machine to turn the

chips into pulp. On the next step, the pulps will be mixed with water and poured onto the

paper machine, and dry them to make the fibers bonded together. The products will be

firstly taken to do some tests by the researcher then be transported to the markets for

consumers.

It takes over 40% of all global industrial wood trade [2], and there is also a big

challenge for such a big industry which is corrosion. Since there are many chemical

solutions been used in the pulp-making process, including acidic solutions, it impossible

to avoid the corrosion attack on the machines. As shown in Figure 1a [3], corrosion costs

and strategies development for pulp and paper industry in the US is $6 billion which is

34% of the overall costs in 2002. The pie chart also indicates that pulp and paper industry

takes the greatest portion of the cost due to corrosion, and it is important to study the

corrosion behavior and find strategies to prevent corrosion to reduce the cost.


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Figure 1a Corrosion Costs and Preventative Strategies in the US (2002)

1.2 Paper Machine Component (suction roll and couch roll)

The parts being analyzed are the section roll and couch roll, and they are normally

located at the ends of the drainage section and in the press section. Suction roll and couch

roll have the structure of a hollow shell with holes which have a diameter of 4 to 5 mm.

In drainage section, a vacuum is pulled on a suction box which is connected to the hollow

shell roll, and water and other liquid contents are drawn from the holes into the suction

box to dry the paper sheet preliminarily [4]. And then in the press section, the remaining

liquid is pressed and squeezed out of the paper sheet to dry the paper sheet further. After

the press section, paper sheet basically reaches to a completely dry state. Suction roll and

couch roll are also used in this process by squeezing and drawing the liquid into the

suction box with vacuum [4]. Figure 1b shown below is a picture of stainless steel suction

rolls in the paper machine [5].


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Figure 1b Stainless Steel Suction Rolls

The material used to construct suction roll and couch roll is centrifugally cast 1N

bronze alloy, and it normally has the composition of 85% of copper, 5% of lead, 5% of

tin and 5% of zinc. It is selected to construct suction roll and couch roll for paper

machine due to its casting properties, on the other hand, the corrosion attack from the

white water is a serious problem for this material [6]. Corrosion normally happens at the

surface around the suction holes since it is always exposed to the liquids during the

papermaking process. Due to the limitation of technologies for suction roll and couch roll

fabrication in the past, cast 1N bronze was selected as the material to fabricate material

for the hollow shell in the 20th century. Nowadays, duplex stainless steels are used to

fabricate the hollow shell which could as prevent corrosion and extend service time of the

paper machine suction roll and couch roll.

1.3 Paper-machine White Water

White water is a chemical aqueous produced in the pulp and paper manufacturing,

and it has a pH of 4.5 with a working temperature of 50oC, and the composition of the

white water is 20 to 200 ppm of Cl-, 100 ppm of SO42- and 10 ppm of S2O3

2-. In the past,

when Na2S2O3 was not yet introduced into the white water, chloride ion (Cl-) was

considered to be the major contributor for the corrosion in white water environment. It


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was considered as a mildly corrosive environment for bronze suction roll and couch roll

because the weak acidic environment with chloride ion in the aqueous solution could not

cause a spontaneous reaction for the dissolution of copper which was the corrosion of

copper in the standard state. Then, thiosulfate ions (S2O32-) is introduced into the white

water due to its pulp-brightening ability as the form of a salt, sodium thiosulfate

(Na2S2O3). However, thiosulfate ions, as a promoter, can also cause corrosion on the

bronze suction roll and couch roll [7]. After adding Na2S2O3 deliberately into the white-

water environment, the corrosion attack is more aggressive and causes extensive damage

to a paper machine. It is essential to apply corrosion resistant methods to protect the

bronze roll when the thiosulfate concentration exceeds 20 ppm.

2.0 Problem Statement

2.1 Composition of Material

As mentioned in section 1.2, the material used to make the suction roll and couch roll

is centrifugally cast 1N bronze alloy. On the other hand, linear polarization resistance

(LPR) method is applied, and LPR result can also be determined with the measurements

of weight loss of the bronze electrodes in the white water. The composition of both 1N

bronze sample and LPR bronze electrode is shown in Table 2a [6],

Composition (wt%) Cu Sn Zn Pb Ni

1N Bronze Sample 85 5 5 5 0

LPR Bronze

Electrode

86.2 4.1 4.2 4.9 0.6

Table 2a Composition of Centrifugally Cast 1N Bronze Alloy and LPR Bronze Electrode


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2.2 Corrosion Mode

Since bronze suction roll and couch roll are exposed in the wet and acidic

environment with thiosulfate salt dissolved in the solution, it can be considered as

aqueous corrosion. Figure 2b indicates that the corrosion attack is uniformly distributed

on the exposed surface. In Figure 2c, the hole size for the corroded (bottom) region is

greater than the non-corroded (top) region. There are multiple black streaks separated on

the surface which are also shown in Figure 2c. In both figures, there is no sign of

localized corrosion attack and there is not any films and shell on top of the roll as well, so

the corrosion mode is general (uniform) corrosion for this bronze suction roll and couch

roll case.

Figure 2b Corroded Surface (1) Figure 2c Corroded Surface (2)

2.3 Critical Factors and Mechanism

There are majorly two ways to determine the critical factors and the mechanism of this

corrosion mode, which are the corrosion rate and potential factors comparison and SEM

analysis.

The first method is to conduct multiple experiments to compare the corrosion rate with

potential factors. The aggressive corrosion on the bronze suction roll and couch roll is

caused by the thiosulfate salt in the white water. In order to determine the correlation

between the instantaneous corrosion rate of bronze and thiosulfate ion concentration is to


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generate the plot of corrosion rate vs. thiosulfate ion concentration and come up with the

linear regression equation. Figure 2d presents the result of such experiment, and the linear

regression equation is [6],

𝐶𝑜𝑟𝑟𝑜𝑠𝑖𝑜𝑛 𝑟𝑎𝑡𝑒 (𝑚𝑝𝑦) = 1.0 + 0.69[𝑝𝑝𝑚 𝑆2𝑂32−];

1 𝑝𝑝𝑚 = 1 𝑚𝑔/𝐿𝑖𝑡𝑒𝑟;

Figure 2d Linear Regression for Corrosion Rate vs. Thiosulfate Ion Concentration for Cast 1N Bronze

Sample

However, since the composition of white water is 20 to 200 ppm of Cl-, 100 ppm of

SO42- and 10 ppm of S2O3

2-, a multiple linear correlation among the corrosion rate of bronze,

concentration of thiosulfate, chloride and sulfate ion can also be obtained as the plot shown

in Figure 2e, and the linear regression equation is [6],

𝐶𝑜𝑟𝑟𝑜𝑠𝑖𝑜𝑛 𝑟𝑎𝑡𝑒 (𝑚𝑝𝑦) = −14.7 + 0.7[𝑝𝑝𝑚 𝑆2𝑂32−] − 0.05[𝐶𝑙−] + 0.04[𝑆𝑂4

2−];


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Figure 2e Linear Regression for Corrosion Rate vs. White Water Element Concentrations for Cast 1N Bronze

Sample

From Figure 2e and its linear regression equation, it implies that the concentration of

chloride and sulfate ion concentrations have an insignificant impact on the corrosion rate

of the Bronze sample comparing with thiosulfate.

The second method is to analyze the corroded sample under scanning electron

microscopy (SEM). Since the black corrosion product is interspersed uniformly on the

bright yellow metal surface, some useful information might appear with SEM analysis.

Figure 2f shows the corroded surface of the bronze sample, and Figure 2e is an X-ray

energy spectrum result showing the composition of the corrosion surface in Figure 2f. The

corroded part is majorly sulfur and copper, which indicates that the corrosion product is

copper sulfide [6].


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Figure 2f Surface of 1N Bronze Sample (280×) Figure 2e XES of Corrosion Product

Figure 2g is the cross section view of the tested LPR bronze electrode sample, and the

bright spots on the surface are the mixture of copper-zinc-tin alloy with metallic lead [6].

Figure 2g Cross Section of LPR Electrode (20×)

Figure 2h provide a closer view of the LPR bronze electrode sample in Figure 2g at a more

specific region, and several X-ray energy analysis spectrums at different locations are

conducted to analyze the chemical composition at these locations in order to determine the


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critical factors of the corrosion. The first spot is the chosen at location 6 which is in a non-

corroded area, and it shows the peaks for copper, zinc, and tin in Figure 2i. The peak for

gold is tracked from the coating for SEM analysis which is irrelevant for the result. Figure

2j shows the X-ray energy analysis spectrum analysis at location 2, and it indicates the

existence of metallic tin. Figure 2k proves the formation of zinc sulfide at location 3 [6].

Figure 2h Surface of LPR Electrode (320×) Figure 2i XES at Location 6 in Figure 2h

Figure 2j XES at Location 2 in Figure 2h Figure 2k XES at Location 3 in Figure 2h


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For an even closer view of Figure 2h, Figure 2l is generated, and the major focuses are on

location 1 and 2. Figure 2m at location 1 shows a similar to the composition of the alloy

(Figure 2i). However, Figure 2n indicate that both tin and copper have significant

composition at location 2 [6].

Figure 2l Surface of LPR Electrode (1100×) Figure 2m XES at Location 1 in Figure 2l

Figure 2n XES at Location 2 in Figure 2l


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With the SEM analysis, it proves that the major corrosion products from white water are

zinc sulfide and copper sulfide, which also proves that thiosulfate ion has a significant

impact on the corrosion of bronze suction roll and couch roll.

There are many other factors for the corrosion on 1N bronze material, and there are

multiple testing methods to determine the correlation. The linear polarization resistance

(LPR) method mentioned previously is applied to determine the relationship between

corrosion rate and time. However, the results are similar for both testing samples because

they almost have an identical composition, and the result can be used for the comparison

between 1N bronze alloy with different materials. Temperature is also a potential factor,

but the service temperature is set as 50oC. Service time and temperature are fixed in this

case, which means that they cannot be varied to reduce the corrosion rate.

In conclusion, the critical factors that drive this corrosion are the concentration of

thiosulfate ion. Thiosulfate ion in white water causes the corrosion of 1N bronze suction

roll and couch roll, and zinc sulfide and copper sulfide are presented on the corroded

region. The result indicates that copper and zinc are removed while tin and lead particles

are not affected by this type of corrosion. The corrosion behavior is the dissolutions of

copper and zinc with the reprecipitations of copper sulfide and zinc sulfide, and the black

streaks in Figure 2c are the corrosion attacked region by thiosulfate ion. Chloride and

sulfate only have an insignificant impact for 1N bronze suction roll and couch roll.


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3.0 Solution for Corrosion Control

3.1 Material Selection

Since 1N bronze alloy can be corroded aggressively by thiosulfate ion in white water,

one solution is to find a substitutional material to construct suction roll and couch roll in

the paper machine. One of the candidates is aluminum bronze, and its chemical

composition is shown as below in Figure 3a, as well as 1N bronze [8],

Composition (wt%) Cu Sn Zn Pb Ni Al Fe

1N Bronze 85 5 5 5 0 0 0

Aluminum Bronze 83 0 0 0 5 9 3

Figure 3a Composition of 1N Bronze and Aluminum Bronze

A 6-week laboratory immersion test and a 1-year laboratory immersion test are conducted

for the comparison of 1N bronze and aluminum bronze, and the immersion testing

conditions are listed in Table 3b [8],

Immersion test

Ionic Species 6-weeks 1-year

Chloride (ppm) 50 400

Sulfate (ppm) 500 800

Thiosulfate (ppm) 0, 5, 10, 25, 50 35

Test Temperature (oC) 50 54

pH at 25 oC 4 4.1

Table 3b Immersion Tests Conditions


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Comparing Figure 3c and 3d, aluminum bronze has lower corrosion rate in different

thiosulfate concentrations in the 6-week immersion test. In figure 3e, it also compares the

maximum pit depth between these two materials at different thiosulfate concentration for

the 6-week immersion test as well [8]. The result also indicates that aluminum bronze has

much better performance regarding corrosion resistance.

Figure 3c 1N Bronze Corrosion Rate Result Figure 3d Aluminum Bronze Corrosion Rate Result


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Figure 3e Comparison for Pit Depth Figure 3f Corrosion Rates Comparison

The result for the 1-year immersion test is shown in Figure 3f [8], and it indicates that the

corrosion rate of 1N bronze is higher than the aluminum bronze in the initial 150 days.

However, 1N bronze has slightly lower corrosion rate than aluminum bronze in the rest of

the test.

In conclusion, aluminum bronze has great corrosion resistance in a short time period,

but it is not the best candidate for a 5-year service time material because the corrosion rate

for aluminum bronze is close to 1N bronze after 150 days of immersion.

Couple other cast alloys are tested to determine the best candidate to replace 1N bronze

as suction roll and couch roll. Their compositions are listed in the table 3g shown below

[7],


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Cast Alloys Cr Ni Mn C Si P S Mo Fe

CA-15 (wt%) 12.3 0.4 0.7 0.11 0.60 0.038 0.027 0.47 Bal.(1)

CA-15S (wt%) 12.3 0.2 1.3 0.18 0.39 0.012 0.201 0.04 Bal.(2)

KCR-A171

(wt%)

24.4 8.1 0.9 0.07 1.55 0.028 0.015 1.08 Bal.

Alloy 75 (wt%) 25.9 6.5 0.6 0.02 0.66 0.020 0.010 0.03 Bal.

(1) 0.04 Se

(2) 0.04 Se

Table 3g Composition of Cast Alloys for Suction Roll and Couch Roll

In the environment of 40-day immersion in white water with a chloride concentration of

20 ppm and a sulfate concentration of 100 ppm, at pH 4.5, and temperature of 50oC, the

correlation between corrosion rate and thiosulfate concentration amount these cast alloys

are shown below in Figure 3h [7],

Figure 3h Corrosion Rate Comparison

Figure 3h shows that both Alloy 75 and KCR-A171 have great corrosion resistance

regarding the thiosulfate ions, and for this specific case that the concentration of thiosulfate

in the white water is 10 ppm, KCR-A171 seems to have lower corrosion rate at this specific


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thiosulfate concentration comparing with Alloy 75. From Figure 3h, it shows that KCR-

A171 is not affected by thiosulfate ions in the white water environment.

In conclusion, Duplex steel KCR-A171 is the best substitutional to replace 1N bronze

as suction roll and couch roll because it has an extremely low corrosion rate regarding

thiosulfate ion. However, there would be localized corrosion attack for instance, pitting

corrosion, on the surface due to the long immersion time in an acidic environment.

3.2 Environment Control

The corrosion rate of cast 1N bronze suction roll and couch roll depends on the white

water temperature, and the corrosion rate can be controlled by variating the temperature.

As the temperature of the white water rises up, the molecules in both bronze suction roll

and white water are more active, and the corrosion rate is going to increase. Likewise,

dropping the service temperature and white water temperature can reduce the corrosion

rate of 1N bronze [9].

In order to reduce the corrosion on the 1N bronze suction roll and couch roll, it is

necessary to modify the composition of white water, especially thiosulfate ion

concentration. Lower the concentration of thiosulfate ion in white water can be helpful for

reducing the aggressiveness of the corrosion on the surface.

It would also ideal to have a drying mechanism, so the contact time between white

water and suction roll or couch roll can be reduced, and the corrosion on the surface can

also be minimized because the corrosion cannot occur on a dried surface. It can be applied

with higher vacuum since vacuum can suck the moisture into a suction box. It can also be

applied with a moisture absorber to make sure the surface stays dry.

Sodium hydrosulphite may be used in powder form or a liquid solution having a

stabilizer and chelating agent in the grinding machine or may be prepared in situ from

sodium borohydride. From time to time, the resulting brighteners may contain large

amounts of thiosulfate. More generally, during storage to produce thiosulfate, especially


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when the alkali hydrosulphite stored in refrigeration, when extended or insufficient. For

example, in summer, warm weather and hot water may be added to promote the formation

of thiosulfate during storage sulphite. Lightening the dough in the tower or tank is usually

carried out, in which the lower pH and application rate can produce an excess of thiosulfate.

Before the headbox can hydrosulphite guide its biodegradable and form thiosulfate

machine which can occur higher application rates and bleaching dressings. In the 1980s,

the industry was rapidly implementing better sulphite generation, storage, and brightening

practices, as described above, to minimize thiosulfate contamination of white water. Better

white water sampling and analysis techniques have also been developed to validate good

practices. The recommended maximum concentration of 5ppm thiosulfate is determined as

the 304L machine as a working guide. Machines that cannot consistently meet this level

are upgrading the 316L pipe and the better stainless steel suction cups. In fact, some bronze

beds which has 30 years of history are still running on hydrosulphite machines, proving

that, by careful attention to detail, good sulfite practices can consistently successfully

control thiosulfate corrosion. Compared with 25 years ago, more wet-end additives are

used in newsprint manufacturing. Additives are used to control the formation, retention,

and contaminants, and most of them do not affect white water corrosivity. Some other

chemical changes are indeed beneficial. Neutral papermaking refers to the use of

precipitated calcium carbonate (PCC) in mechanical pulp furnish. The conversion from the

traditional pH 4.5 to pH 7 by itself is almost no different from the corrosion view. However,

PCC introduces significant levels of bicarbonate in white water and will tend to inhibit

304L corrosion, albeit not bronze. Some factories intentionally added sodium

hydrosulphite to affect the whiteness of the pulp. This will also suppress pitting in

304L.New hydrosulphite sources, safe-related pressures to avoid liquid SO2 use in the

plant and the general push to reduce chemical costs are recent changes that may affect

thiosulfate levels. Many old machines still run bronze rolls, with some 304L pipes or boxes.

Continuing to note that good sulphite practice is necessary to avoid thiosulfate corrosion


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and to ensure that all hydrosulphite meets its intended purpose of whitening mechanical

pulp. In additional, the key to a successful pulp and paper plant is reducing costs without

compromising production and quality. Reclaiming white water is one of the best ways to

do this. Roughly 30% of pulp stock ends up as white water. Treatment of the white water

is necessary for its important reuse in other areas of the plant. pH control is the most

efficient method to treat reclaimed white water [10].

In conclusion, it is impossible for suction roll and couch roll to stay dry for a longer

time because there is always moisture on the surface when the production line is operation.

The better option is to reduce the concentration of thiosulfate ion as much as possible or

find another substitutional pulp-brightener which is less corrosive to the 1N bronze surface.

Nowadays, pulp and paper industry still rely on hydrosulfite for pulp-brightening, but a

modified method or formula for white water can be applied to control corrosion rate.

3.3 Technological Control

Thiosulfate concentrations can be controlled by a careful control of the pulp

brightening process. Reducing hydrosulfite retention time, eliminating air contact,

reducing hydrosulfite storage temperature, and eliminating thiosulfate in hydrosulfite

supplies can reduce thiosulfates to acceptable levels in white water derived from

groundwood pulp [11].

A non-metallic coating such as TeflonTM PTFE coating, could be helpful to reduce the

corrosion attack on the surface because it blocks the contact area between white water and

1N bronze. PTFE coating is extreme non-reactive regarding general acids, and like other

liquids, the white water moisture does not stick on the PTFE coating surface [12].

The inhibitor is another option, for instance, mercaptobenzotriazole inhibitor can be

applied in roll showers to control bronze corrosion [7]. Sodium mercaptobenzotriazole is

often added as a corrosion inhibitor in recirculating water for industrial equipment that

contains copper components. In addition, a recent study found that benzotriazole is


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extremely effective in the aqueous environment. It can form a strongly bonded

chemisorbed two-dimensional barrier film less than 50 angstroms thick. This insoluble film

can from as a monomolecular layer protects copper and its alloys in aqueous media [13].

In conclusion, PTFE coating provides a great physical barrier between 1N bronze and

white water, but the heavy-duty manufacturing process can damage the coating in a very

short time. On the other hand, it is expensive to develop inhibitors for corrosion prevention.

4.0 Failure Prevention

After comparing material selection method, environmental control method, and

technological control method, it indicates that the modification of white water is relatively

hard to achieve, and it is not possible to avoid thiosulfate ion formation during white water

treatment. It is difficult to change the working environment or temperature during the pulp

and paper making process, so it requires a lot of effort to achieve a little impact on the

environmental control. PTFE coating is also not reliable in a long term due to the excessive

wear of the suction roll and couch roll, it is too expensive to maintain and repair the PTFE

coating in every short time of period. It is also expensive to develop inhibitors to prevent

thiosulfate corrosion attack, and application of an inhibitor is only necessary when the

instantaneous corrosion rate of bronze in white water is greater than 0.5 mm/y. However,

the instantaneous corrosion rate for the 1-year immersion test 1N bronze sample is

approximately 0.5 [8], so inhibitor is only applicable for materials with even higher

instantaneous corrosion rate.

The team recommendation is to switch the suction roll and couch roll to duplex steel

KCR-A171 which has constant low corrosion rate (close to zero) and the corrosion rate of

this material does not change with thiosulfate concentration as well. It is the best solution

because it is a cast steel material which is easy to be fabricated into the suction roll and

couch roll shape, and the material itself has a relatively low cost comparing with other


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materials and corrosion prevention methods. With KCR-A171, the service time of the

suction roll and couch roll can be extended which can help the industry to reduce the cost

of corrosion.


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Reference

[1] Pulp and Paper Industry, Historica Canada, (2006 Feb. 07), Retrieved from:

http://www.thecanadianencyclopedia.ca/en/article/pulp-and-paper-industry/

[2] Pulp and Paper, WWF, Retrieved from: http://www.worldwildlife.org/industries/pulp-and-paper

[3] “Corrosion Costs and Preventative Strategies in the US,” A Supplement to Materials Performance,

NACE, Houston, TX, July 2002

[4] Various. “Paper Machine Operations Short Course Notes”. Technical Association for the Pulp and Paper

Industry. TAPPI Press. 2004.

[5] Figure of Stainless Steel Suction Rolls, Retrieved from:

http://www.rifspa.it/images/pagine/full/forature_003.jpg

[6] Angela Wensley, Harry Dykstra & Alicja Augustyn. “Corrosion Monitoring in Paper Machine White

Waters”. Engineering & Papermakers Conference. Richmond, BC, Thunder Bay, ON, Canada. 1997.

[7] Garner, A. “Thiosulfate Corrosion in Paper-Machine Whiter Water”. Pulp & Paper Research Inst of,

Canada, Point Claire, Que, Can, Pulp & Paper Research Inst of Canada, Point Claire, Que. Can. Corrosion,

v41, n 10, P 587-591, Oct 1985.

[8] P. E. Glogowski & A. P. Castillo. “Evaluation of cast bronze alloys in paper mill white waters”. Tappi

Journal, Vol 71, No. 6. June 1988.

[9] “Bronze: Characteristics, Uses And Problems”, Aug 5, 2016. Retrieved from:

https://www.gsa.gov/portal/content/111994

[10] “Thiosulphate and Paper Machine Corrosion”. Pulp and Paper Canada. N.p., n.d. Web. 13 Dec 2016.

[11] R. A. Yeske. “Corrosion in the Pulp and Paper Industry”. IPC Technical Paper Series, Number 192.

July,1986. Retrieved from: https://smartech.gatech.edu/bitstream/handle/1853/2697/tps-192.pdf

[12] “Teflon PTFE Fluoropolymer Resin Properties Handbook”. Retrieved from:

http://www.rjchase.com/ptfe_handbook.pdf

[13] “Benzotriazole: An effective corrosion inhibitor for copper alloys”. Copper Development Association.

Retrieved from: https://www.copper.org/publications/pub_list/pdf/a1349.pdf

http://www.thecanadianencyclopedia.ca/en/article/pulp-and-paper-industry/

http://www.worldwildlife.org/industries/pulp-and-paper

http://www.rifspa.it/images/pagine/full/forature_003.jpg

https://www.gsa.gov/portal/content/111994

https://smartech.gatech.edu/bitstream/handle/1853/2697/tps-192.pdf

http://www.rjchase.com/ptfe_handbook.pdf

https://www.copper.org/publications/pub_list/pdf/a1349.pdf

matls 4d03 case study #2

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