Localised corrosion of stainless steels depending on chlorine dosage in chlorinated water

acom 3-211 A corrosion management and applications engineering magazine from Outokumpu Localised corrosion of stainless steels depending on chlorine dosage in chlorinated water Introduction The European Drinking Water Directive sets a maximum limit of 25 ppm for chlorides in drinking water but does not contain guidelines for chlorine. The WHO drinking water standard states that 2 3 ppm chlorine should be added in order to gain a satisfactory disinfection and adequate residual concentration. The residual chlorine has a significant influence on the corrosion behaviour of stainless steels and may have detrimental consequences in the form of localized corrosion if an inappropriate stainless steel grade is used. This article clearly demonstrates that the novel duplex grades LDX 211 and LDX 244 provide attractive alternatives for handling potable water and cooling water. They also have a price less affected by nickel price fluctuations and higher strength compared to the standard austenitic grades 437 and 444. In 3-day laboratory tests, the lean duplex grade LDX 211 performed as well as or better than 437 at both 3 C and 5 C. It is also shown that the presence of crevices strongly increases the risk for localized corrosion in a chlorinated environment. www.outokumpu.com

2 Localised corrosion of stainless steels depending on chlorine dosage in chlorinated water Sukanya Mameng, Rachel Pettersson, Outokumpu Stainless AB, Avesta Research Centre, Avesta / Sweden Summary In drinking water systems the main stainless steel grades used are the standard austenitic stainless steel grades 437 (34L) and 444 (316L), with the grade selection depending on the chloride and chlorine levels in the water. The lean duplex grades LDX 211 and LDX 244 provides attractive alternatives, with a more stable price and higher strength level, but there is little available data on their use in drinking water systems. The European Drinking Water Directive sets a maximum limit of 25 ppm (mg/l) for chlorides in drinking water but does not contain guidelines for chlorine. Drinking water is normally treated to give a residual level of.2 to.5 ppm of chlorine to kill bacteria, but the actual concentrations added are usually higher. The WHO drinking water standard states that 2 3 ppm chlorine should be added to water in order to gain a satisfactory disinfection and adequate residual concentration. For a more effective disinfection the residual amount of free chlorine should exceed.5 ppm after at least 3 minutes of contact time at a ph value of 8 or less. The residual chlorine has a significant influence on the corrosion behavior of stainless steels. The remaining of residual chlorine in drinking water is a major factor leading to the ennoblement of the natural potential of stainless steel. This oxidizing effect of chlorine may have detrimental consequences in that stainless steels may suffer from localized corrosion if an inappropriate grade is used. The aim was to understand and determine to what extent residual chlorine levels at various chloride contents will affect the localized corrosion behaviour of the standard austenitic stainless steel grades 437 and 444, also the duplex grades LDX 211, LDX 244 and 225. A simulated chlorination system was created in which the specimens were immersed for 3 days at 3 C and 5 C at chloride levels of 2 ppm and 5 ppm, with residual chlorine levels of.2,.5 and 1 ppm at ph 6.5 7.5. The specimens were investigated by visual examination and microscopy. The duplex grades LDX 244 and 225 perform very well in all the chlorinated environments tested. The lean duplex grade LDX 211 performed as well as or better than 34L at both 3 C and 5 C. The results also indicated that the presence of a crevice increased the risk for localized corrosion in a chlorinated environment. This study demonstrates that duplex stainless steels are good candidates to use in water pipes or water storage tanks. Keywords: drinking water, chloride, chlorination, total residual chlorine (TRC), localised corrosion, stainless steel.

3 1 Introduction Stainless steel use for drinking water applications is increasing in the world. Stainless steels offer several advantages compared to other materials, such as mild steel, cast iron and copper which have been used for decades. First of all, stainless steels have generally excellent corrosion resistance and require little maintenance. There is no need for any protective coating or any protective system. Correct grade selection and good practice will minimize the risk of any localized corrosion. Therefore there is practically no contamination of water in contact with stainless steel, as has been demonstrated in the investigation [1] shown in Figure 1. Fig. 1 Nickel (Ni) and Chromium (Cr) content of water drawn from stainless steel water systems in a Scottish hospital [1]. 2 Metal content of water (µg/l) 18 16 14 12 1 8 6 4 Ni from 34 - Cold water Ni from 316 - Cold water Ni from 34 + 316 - Hot water Cr from 34 - Cold water Cr from 316 - Cold water Cr from 34 + 316 - Hot water 2 1 2 3 4 11 18 Days in use 25 32 18 125 Figure 1 show the leaching values for Cr and Ni were less than 5% of the maximum levels permitted by the European Drinking Water Directive (5 and 2 μg/l respectively) [2]. The low leaching levels from the use of stainless steel in the drinking water system are clearly of benefit in this situation. Another point to be considered is the mechanical properties. The good ductility, strength and weldability enable the use of lightweight structures, for example thin walled tubes. Among the stainless steels, the duplex materials exhibit much higher mechanical strength than corresponding austenitic grades as shown in Table 1. Compared to other materials used for applications in the potable water distribution network, duplex grades Minimum mechanical strengths at 2 C of hot rolled plate/cold rolled strip and sheet according to EN 188-4 and EN 128-7 when applicable [3, 4, 5]. Table 1 Outokumpu EN.2% Yield Strength Tensile Strength Elongation steel names Designation MPa MPa % Austenitic 431 1.431 21/23 52/54 45/45 437 1.437 2/22 5/52 45/45 441 1.441 22/24 52/53 45/4 444 1.444 22/241 52/531 45/41 Duplex LDX 211 1.4162* 48/53 68/7 3/3 LDX 244 1.4662** 55/55 75/75 25/25 225 1.4462 46/5 7/7 25/2 * LDX 211 is not yet listed in EN 128-7. ** LDX 244 is not yet listed in EN 188-4 or EN 128-7. Data for LDX 244 corresponds to the internal standard AM 641.

4 allow a reduction in wall thickness and consequently reduces investment costs. All together stainless steels give a life cycle cost benefit. The two main alloying elements of stainless steels are chromium (Cr) and nickel (Ni). From a general point of view, chromium improves the pitting corrosion resistance whereas nickel additions are made for controlling microstructure. Further alloying elements may be added like molybdenum (Mo) for increasing pitting resistance or nitrogen (N) for improving mechanical properties and resistance to pit initiation. Depending on the stainless steel composition and chloride content of water, these materials may be resistant to aqueous corrosion in a wide range of ph at ambient temperature. Stainless steels ability to resist pitting corrosion may be estimated by calculation of the Pitting Resistance Equivalent Number (PREN). Equation (1) gives the most frequently employed formula for PREN calculation. PREN= Cr (%) + 3.3 Mo (%) + 16 N (%) Equation (1) In drinking water systems the main stainless steel grades used are the standard austenitic stainless steel grades 437 and 444. The grade selection depends on the chloride levels of the water and also on the severity of the crevices the materials are exposed to, as shown in Table 2 from the Nickel Development Institute. The chloride content of the water is the most important parameter because of its influence on localized corrosion, crevice corrosion in particular. The European Drinking Water Directive sets a maximum limit of 25 ppm (mg/l) for chlorides in drinking water but does not contain guidelines for chlorine [2]. Chloride level guidelines for waters at ambient temperatures [6]. Table 2 Chloride level (ppm, mg/l) Suitable grades <2 1.431 (34), 1.437 (34L), 1.444 (316L) 2 1 1.444 (316L), 1.4462 (225) 1 36 1.4462 (225), 6% Mo Super austenitic, Super duplex >36 and sea water 6% Mo Super austenitic, Superduplex 2 Water Chlorination Chlorination is a one of many methods that can be used to disinfect water and control bacteria. Sodium hypochlorite (NaOCl) is the form of chlorine normally use for chlorination process because it is cheap and easy to dose. When chlorine added to water, it immediately begins to react with compounds found in the water to give hypochlorous acid (HOCl) and hypochlorite (OCl - ). The remaining amount is called free residual chlorine. The free residual chlorine is typically measured in drinking water disinfection systems to find if the water contains enough disinfectant. Typical levels of free chlorine in drinking water are.2.5 ppm [7], but the actual concentrations added are usually higher. The WHO drinking water standard states that 2 3 ppm chlorine should be added to water in order to attain a satisfactory disinfection and maintain residual concentration [8]. The maximum amount of chlorine one can use is 5 ppm. For effective disinfection the residual amount of free chlorine should exceed.5 ppm after at least 3 minutes of contact time at a ph value of 8 or less. The residual chlorine has a significant influence on the corrosion behaviour of stainless steels. The remaining residual chlorine in drinking water is thought to be a major factor leading to the ennoblement of the natural potential of stainless steel. This oxidizing effect of chlorine may have detrimental consequences and stainless steels may suffer from localized corrosion if an inappropriate grade is used.

5 This work was conducted to understand and determine to what extent total residual chlorine levels at various chloride contents will affect the pitting and crevice corrosion behaviour of the standard austenitic stainless steel grades 437 and 444, also the duplex grades LDX 211, LDX 244 and 225. The recently introduced duplex grades LDX 211 and LDX 244 provide an attractive alternative, with a more stable price and higher strength level, but there is little available data on their use in drinking water systems. 3 Materials and experimental technique 3.1 Materials The materials used in this study are 437, 444, LDX 211, LDX 244 and 225 which were all tested as plain (sheet), welded and creviced samples. The surface finish, thickness, PREN values and the chemical composition of these materials are reported in Table 3. Steel grades, surface finish, thickness, PREN values and the chemical composition for materials used in long term chlorination. Table 3 Outokumpu EN Product Thickness Typical composition, weight-% steel names EN Conditions (mm) PREN 16 C Cr Ni Mo N Others 437 1.437 2B 3 18.1.2 18.1 8.1 444 1.444 2B 3 24.1.2 17.2 1.1 2.1 LDX 211 1.4162 2E 3 26..3 21.5 1.5.3.22 5Mn LDX 244 1.4662 2E 3 33.6.2 24. 3.6 1.6.27 3Mn 225 1.4462 2E 3 35..2 22. 5.7 3.1.17 2B: Cold rolled, heat treated, pickled, skin passed 2D: Cold rolled, heat treated, pickled 2E: Cold rolled, heat treated, mech. desc, pickled 3.2 Long-term chlorination experiments Coupons of duplicate plain (sheet), welded and crevice specimens with size 6x3x3 mm were used with an as-received surface as show in Figure 2A. All cut edges were wet ground to 32 mesh. The crevice samples had a 12 mm hole placed in the centre of the sample. Samples were bolted together with INCO crevice formers on both sides of specimen (Figure 2B). All crevice formers were tightened with a torque of 1.58 Nm. It was verified that there was no electrical contact between the samples and the screw. Plain (sheet) and welded specimens were suspended in the solution on platinum wires to minimize crevice effects when investigating pitting corrosion. Fig. 2 Coupons of plain (sheet), welded and crevice specimens used for long term testing. Fig. 2A Fig. 2B Sheet Weld Crevice

6 Chemical compositions of GTAW filler (typical values, %) [9]. Table 4 Welding wire TIG Base Nominal composition, weight-% (EN ISO designation) Material C Cr Mo Ni N Si Mn Avesta 38L-Si/MVR-Si (W 19 9 L Si) 437.2 2. - 1.5 -.85 1.8 Avesta 316L-Si/SKR-Si (W 19 12 3 L Si) 4432.2 18.5 2.6 12. -.85 1.7 Avesta LDX 211 (W 23 7 L) LDX 211.2 23. <.5 7..14.4.5 Avesta 225 (W 22 9 3 N L) LDX 244.2 23. 3.1 8.5.17.5 1.6 Avesta 225 (W 22 9 3 N L) 225.2 23. 3.1 8.5.17.5 1.6 The welded samples were obtained by tungsten inert gas welding (TIG). The welding was done with filler material and welding conditions as specified in Table 4 and Table 5 below. This welding process is often used for water applications. All samples have the same thickness of 3 mm. Weld samples were pickled in mixed acid (3M HNO 3 and 3M HF). Chloride (Cl - ) containing electrolytes with various total residual chlorine (TRC) levels, at ph 6.5-7.5, were prepared from distilled water. Chloride ions were added to the level of 2 ppm and 5 ppm as sodium chloride (NaCl). The solutions were dosed with a stock solution containing 1 ppm of sodium hypochlorite to obtain various predetermined total residual chlorine concentrations. Total residual chlorine (TRC) is defined as the sum of hypochlorous acid (HClO) and hypochlorite ion (ClO - ) concentrations.the amount of residual chlorine was measured with a colorimeter using the diethyl-p-phenylene diamine (DPD) method [1]. Three total residual chlorine concentrations were investigated that correspond to the residual concentration typically used for water disinfection treatments:.2,.5 and 1 ppm. The open circuit potential (OCP) was monitored for 3 days in the test solutions with the different residual chlorine levels and a temperature of 3 C or 5 C. The chlorine was dosed once every 5 7 days to maintain the residual chlorine level. After testing the specimens were examined and the depth of maximum attack was measured with a light optical microscope. A depth exceeding.25 mm was defined as localised corrosion. Welding condition of welded specimens. Table 5 Base Shielding Welding speed Heat input Material gas (cm/min) (kj/cm) Joint design 437 Ar 21.72.64 Butt joint 444 Ar 24.66.6 Butt joint LDX 211 Ar+2% N 2 2.17.64 Butt joint LDX 244 Ar 19.29.69 Bead on plate 225 Ar 2.38.5 Bead on plate Ar: Argon gas, N 2 : Nitrogen gas

7 4 Results and discussion 4.1 Open circuit potentials (OCP). The stainless steel samples were immersed in the test solutions with 2 ppm and 5 ppm chloride at 3 C and 5 C for 24 hours before the start of chlorination. The open circuit potential (OCP) usually stabilised after ~4 hours and was typically found to lie in the range 19 22 mv for the sheet specimens after 24 hours. The values were somewhat higher for the weld and crevice specimens. The addition of sodium hypochlorite gave a strong increase in the open circuit potential. After a certain time, typically 1 24 hours the potential stabilised and the OCP Max could be measured as shown in Figure 3. The result shows that OCP Max increases with TRC level because the oxidising power of the solution increases, Table 6. Fig. 3 Evaluation of maximum open circuit potential in chlorinated water. 8 7 6 OCP Max 72 mv SCE Potential (mv SCE ) 5 4 3 2 1 5 1 15 2 25 3 Time (days) Average OCP Max of five different steel grades in water containing chloride and total residual chlorine at 3 C and 5 C. Table 6 Maximum open circuit potential, OCP Max (mv SCE ) Chloride level.2 ppm.5 ppm 1 ppm TRC,.2 ppm TRC,.5 ppm TRC, 1 ppm TRC, (ppm) Material TRC, 3 C TRC, 3 C 3 C 5 C 5 C 5 C 2 437 425 544 722 429 454 723 444 46 556 794 393 445 683 LDX 211 493 619 819 363 444 679 LDX 244 NT NT 77 NT NT 682 225 48 589 747 362 535 671 5 437 345 594 652 349 347 736 444 375 588 679 356 399 73 LDX 211 37 549 722 427 367 712 LDX 244 NT NT 771 NT NT 72 225 397 625 673 379 486 683 NT = Not tested, TRC = Total residual chlorine

8 The OCP Max after chlorination compared to the situation before chlorination is shown in Figure 4. The increase in OCP was about 2 mv SCE for.2 ppm TRC, about 3 mv SCE for.5 ppm TRC and about 5 mv SCE for 1 ppm TRC. This indicates that even at low TRC concentrations the open circuit potential increases. Fig. 4 The potential increase (OCPMax-OCP) versus total residual chlorine (TRC) after chlorine dosage for all steel grades. 7 Potential increase (mv) 6 5 4 3 2 2 ppm, 3 C 5 ppm, 3 C 2 ppm, 5 C 5 ppm, 5 C 1.2.4.6.8 1. 1.2 Total residual chlorine, TRC (ppm) 4.2. Influence of localised corrosion on OCP for chlorinated water. The occurrence of localised corrosion is frequently seen as a drop in the open circuit potential, as illustrated in Figure 5. After 3 days, visual and microscopy examination showed that pitting had occurred for the welded 437 and LDX 211 (Figure 7A). These both showed a rapid drop in OCP during testing. No corrosion was seen for the welded 225 which maintained a high OCP throughout the test. Fig. 5 Corrosion potential change of TIG welded specimens of 437, LDX 211 and 225 in 5 ppm chloride and 1 ppm TRC at 5 C showing the potential drop associated with the onset of pitting corrosion. 9 8 7 6 5 C, 5 PPM CI-, 1 PPM TRC No Pitting corrosion Potential (mv SCE ) 5 4 3 2 Pitting corrosion 1 437-weld 225-weld LDX 211 -weld Pitting corrosion -1 1 2 3 4 5 6 7 Time (hours)

9 Fig. 6 Corrosion potential change of TIG welded and crevice specimen for 437 and 225 in 2 ppm chloride and 1 ppm TRC at 3 C. 9 8 437-weld 437-crevice 225-weld 225-crevice No Pitting corrosion 3 C, 2 ppm CI -, 1 ppm TRC 7 Potential (mv SCE ) 6 5 4 3 2 No crevice corrosion Pitting corrosion 1 1 Crevice corrosion 2 3 4 5 6 7 Time (hours) Fig. 7 Appearance of localized corrosion after tested in 5 ppm chloride and 1 ppm TRC at 5 C. Fig. 7A TIG welded-ldx211 Fig. 7B Crevice corrosion for 437 Pitting corrosion on the weld Crevice corrosion Figure 6 shows the OCP change of TIG welded and creviced samples of 437 and 225 in 2 ppm chloride and 1 ppm TRC at 3 C. Visual examination showed that localized corrosion had occurred for 437 (Figure 7B) but not for 225. 4.3 Visual examination after 3 days. Samples were examined after exposure in the 2 ppm and 5 ppm chloride solutions with different total residual chlorine levels at 3 C and 5 C for 3 days. A summary of the results from this investigation is shown in Table 7. Where corrosion occurred, the cells are filled dark blue and where no corrosion occurred the cells are light blue. Table 7 show that the lean duplex LDX 211 was found to be at least as resistant as 437. In all experimental conditions tested, the duplex grades LDX 244 and 225 perform very well with no significant localised attack. Both these grades have a high PREN (>3), whereas for the grades with PREN<3 some localised attack was observed. The results show that the alloying elements influence the localised corrosion resistance of stainless steel. For the austenitic steels, the corrosion resistance for molybdenum (Mo) containing grade (444) is higher than for the molybdenum (Mo) free grade (437). A higher chromium (Cr) level in combination with nitrogen (N) addition has the same positive influence for duplex grades.

1 Summary of visible pitting and crevice corrosion in this investigation. Table 7 Test condition Type of specimen Temp. Chloride TRC* 437 444 LDX 211 LDX 244 225 ( C) (ppm) (ppm) P W C P W C P W C P W C P W C 3 2.2.5 1. 3 5.2.5 1. 5 2.2.5 1. 5 5.2.5 1. *TRC = Total residual chlorine, P = Plain (sheet) sample, W = Welded sample, C = Creviced sample No corrosion Corrosion Not tested in this study Crevice corrosion not observed; possibly due to loosening of the screw, but expected based on 3 C results. The results also indicated that the presence of a crevice increases the risk for localized corrosion in chlorinated environments. Special attention should be taken, to avoid crevices in construction, since residual chlorine solution can remain in crevice areas and cause corrosion. 4.4 Comparison with engineering diagrams. Engineering diagrams for a given steel grade as a function of temperature and chloride content are a useful illustration of the risk areas for localized corrosion in drinking water applications [11]. These diagrams are based on a combination of laboratory testing and extensive practical experience and provide a useful reference base for the present investigation. As can be seen in Figure 8 there is excellent agreement between the diagram and the present data Fig. 8 Engineering diagram indicating the maximum temperatures and chloride concentration allowed in slightly chlorinated (<1 mg/l) drinking water for 437 and 444 [11]. C 1 9 437 (34L) Pitting C 1 9 444 (316L) Pitting 8 8 7 7 6 6 5 5 4 4 3 3 2 1 1 1 Chloride, ppm 2 1 1 1 Chloride, ppm Green: No corrosion Red: Pitting corrosion.5 ppm TRC 1. ppm TRC

11 for 444 tested with 1 ppm TRC: pitting corrosion occurred only at 5 ppm chloride and 1ppm TRC at 5 C for the sheet specimen, and this point is above the line. For 437 all four of condition tested showed pitting with 1ppm TRC, and should thus lie above the boundary line. If, however the comparison is made to the.5 ppm data, the curve seems instead slightly too conservative. The overall agreement is thus very good, and underlines the point that the chloride tolerance of different stainless steel grades is very sensitive to the chlorination level. A summary of chlorination limits for different grades from this investigation are shown in Table 8. Chlorination limits which did not cause corrosion in the 3 days immersion tests for different grades depending on chloride content. Table 8 Test condition TRC limits (ppm) for different grades depending on chloride content Temp. Chloride 437 444 LDX 211 LDX 244 225 ( C) (ppm) P W C P W C P W C P W C P W C 3 2.5.5 <.2 1. 1. 1. 1. 1. <.2 1. 1. 1. 1. 1. 1. 3 5.5.5 NT 1. 1..2.5.5 <.2 1. 1. 1. 1. 1. 1. 5 2.5.5.2 1. 1..5.5.5.2 1. 1. 1. 1. 1. 1. 5 5.5.2 NT.5.5.2.5.2 <.2 1. 1. 1. 1. 1. 1. P = plain (sheet) sample; W = welded sample; C = creviced sample; TRC = total residual chlorine; NT= not tested It is important that a material is not exposed to excessive levels of residual chlorine. For effective disinfection the residual chlorine should exceed.5 ppm after at least 3 minutes of contact time [8]. During practical operation, the chloride content will most probably be lower than during this test. Thus, there is a good chance that the 437, LDX 211 and 444 can be used successfully for normal service in water piping systems as long as problematic crevices can be avoided. In doubtful cases upgrading to LDX 244 or 225 may be advisable.

12 5 CONCLUSION In long-term (3 days) immersion tests, the highest alloyed duplex grades 225 and LDX 244 performed very well in the chlorinated environments tested (2 or 5 ppm chloride, 3 C or 5 C). No pitting, crevice corrosion or weld attack was seen in any of the environments for these grades. The lean duplex grade LDX 211 performed as well as or better than 437 (34L) at all conditions tested. In the pitting test it performed as well as 444 (316L) in 2 ppm chloride at 3 C. Chlorine solution with significant residual chlorine concentrations can remain in crevice areas and cause corrosion, and therefore special attention should be taken in construction. The lean duplex steel LDX 211 is a good candidate for water piping systems and tanks, when the water is mildly chlorinated. In more severe condition the higher alloyed LDX 244 or 225 are more suitable. Material selection guidelines depending on chloride content, chlorine dosage and temperature are shown in Table 9 and Table 1 below. In order to ensure good performance deposits and surface contamination should be avoided. Summarised results of 3 day tests in chlorinated solutions containing 2 ppm chloride at 3 C or 5 C. Table 9 BM Weld Crevice 34L 316L 34L 316L (34L) 316L LDX 211 LDX 244 LDX 211 LDX 244 (LDX 211 ) LDX 244 1 Temperature 5 C Temperature 3 C 225 225 225 34L 316L 34L 316L 34L 316L LDX 211 LDX 244 LDX 211 (LDX 244 ) LDX 211 (LDX 244 ) 225 225 (225) 34L 316L 34L 316L 34L 316L LDX 211 LDX 244 LDX 211 (LDX 244 ) LDX 211 (LDX 244 ) 225 225 (225) 34L 316L 34L 316L 34L 316L LDX 211 LDX 244 LDX 211 LDX 244 LDX 211 LDX 244 225 225 225 34L 316L 34L (316L) 34L (316L) LDX 211 (LDX 244 ) (LDX 211 ) (LDX 244 ) LDX 211 (LDX 244 ) 225 (225) (225) 34L 316L (34L) (316L) 34L (316L).5 1.2.5 Chlorine (ppm) LDX 211 (LDX 244 ) (LDX 211 ) (LDX 244 ) LDX 211 (LDX 244 ).2 225 (225) (225) 2 ppm Chloride Red-corrosion, Green-no corrosion, (Red)-possibly corrosion, not tested in this study (Green)-possibly no corrosion, not tested in this study

13 Summarised results of 3 day tests in chlorinated solutions containing 5 ppm chloride at 3 C or 5 C. Table 1 BM Weld Crevice 34L 316L 34L 316L (34L) 316L LDX 211 LDX 244 LDX 211 LDX 244 (LDX 211 ) LDX 244 1 Temperature 5 C Temperature 3 C 225 225 225 34L 316L 34L 316L (34L) 316L LDX 211 LDX 244 LDX 211 (LDX 244 ) (LDX 211 ) (LDX 244 ) 225 (225) (225) 34L 316L 34L 316L 34L 316L LDX 211 LDX 244 LDX 211 (LDX 244 ) LDX 211 (LDX 244 ) 225 (225) (225) 34L 316L 34L 316L (34L) 316L LDX 211 LDX 244 LDX 211 LDX 244 (LDX 211 ) LDX 244 225 225 225 34L 316L 34L (316L) (34L) 316L LDX 211 (LDX 244 ) LDX 211 (LDX 244 ) LDX 211 (LDX 244 ) 225 (225) 225 34L 316L 34L (316L) 34L (316L).5 1.2.5 Chlorine (ppm) LDX 211 (LDX 244 ) LDX 211 (LDX 244 ) LDX 211 (LDX 244 ).2 225 (225) 225 5 ppm Chloride Red-corrosion, Green-no corrosion, (Red)-possibly corrosion, not tested in this study (Green)-possibly no corrosion, not tested in this study 6 REFERENCES [1] C.A. Powell and W.Strassburg, Stainless Steel for Potable Water Service, 2 nd European Stainless Steel Congress, Düsseldorf, 1996. [2] European Drinking Water Council Directive 98/83/EC, Nov, 1998. [3] Outokumpu data sheet, Standard Cr-Ni stainless steel. [4] Outokumpu data sheet, Standard Cr-Ni-Mo stainless steel. [5] Outokumpu data sheet, Duplex stainless steel [6] Peter Cutler, Stainless steel and drinking water around the world, Nickel Development institute (NiDi). [7] The chlorine institute.inc, Chlorine effect on health and the environment, 3 th Edition-Nov.1999. [8] Guidelines for Drinking Water Quality, 3 rd Edition, 28. [9] Avesta Welding handbook, 3 rd Edition-Dec, 27. [1] Pradyot Patnaik, (1995), Dean s Analytical Chemistry Handbook, McGraw Hill, New York. [11] Outokumpu, Corrosion Handbook, 1 th Edition-Nov, 29. Presented at Eurocorr 211 in Stockholm, Sweden

Comments on acom and its articles or suggestions on future articles are appreciated and should be sent to the editor Andreas Persson at acom@outokumpu.com This document is for information only and seeks to provide professionals with the best possible information to enable them to make appropriate choices. Although every effort has been made to ensure the accuracy of the information provided in this document, Outokumpu can not accept any responsibility for any loss, damage or other consequence resulting from the use of this publication. The information provided herein may be subject to alterations without notice. 1491EN-GB Art 58. September 211 Activating Your Ideas Outokumpu is a global leader in stainless steel with the vision to be the undisputed number one. Customers in a wide range of industries use our stainless steel and services worldwide. Being fully recyclable, maintenance-free, as well as very strong and durable material, stainless steel is one of the key building blocks for a sustainable future. What makes Outokumpu special is total customer focus all the way, from R&D to delivery. You have the idea.we offer world-class stainless steel, technical know-how and support. We activate your ideas Outokumpu Stainless AB, Avesta Research Centre Box 74, SE-774 22 Avesta, Sweden Tel. +46 () 226-81, Fax +46 () 226-81 77 www.outokumpu.com