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Materials
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About the authors
M Venkat Ramesh , Global Product Manager , Heat Exchanger tubes , Tubacex , has worked more than 17 years in stainless seamless tube and pipe industry in different roles including Sales , Business development , Key Account , Technical marketing and as Product Manager . He has worked closely with some of the refineries and chemical companies involving suggestions and resolving corrosion issues , material testing , material upgrade suggestions etc . He has published technical articles in Leading Industrial Magazines and presented a paper at NACE in the past .
Shabareesh Nair , Technical Marketing Director-Asia , Tubacex , has a Bachelor ’ s in Mechanical Engineering , and a Post Graduate Diploma in Marketing Management . Having a total industry exposure of 15 years , the last 12 years have been exclusively with the Stainless Steel industry and has been associated with a similar industry before joining Tubacex . At Tubacex , responsibilities include developing hydrogen value proposition in Asia , Technical Marketing support to the regional offices in Asia and identifying and developing new business applications / opportunities .
Degree Centigrade
120 100 80 60 40 20 0
Alloy 625 Alloy 59 Grades N10276 N06022 Graph 3 : CPT in green death solution- ( 8vol .% H 2
SO 4
+ 3vol .% HCI + 1 % CuCl 2 + 1 % FeCl 3
× 6 H 2
O after repeatedly heating for 24 hours using 5 ° C ( 9 ° F ) temperature increments ).
Anhydrous acetic acid can increase the corrosion rate . Hot acetic acid and the presence of chlorides can also increase corrosion rates . Alloy 59 works well in both oxidizing and reducing conditions , making it an ideal candidate for tubes , pipes , and more . The performance of the various alloys largely depends on the characteristics of the contaminants contained in the organic acids , and on operating temperatures . From tests , it was concluded that Alloy 59 is the best material for use in acetic and formic acid up to 300 degrees centigrade .
Flue Gas Desulfurization There are different absorbents used to remove sulfur from exhaust emissions . In most cases , there is a possibility of the formation of sulfuric acid as a byproduct under high temperatures which causes severe corrosion . Alloy 59 works best in these conditions when compared to C alloys . It is the purest form of Cr-Ni-Mo with minimal Fe and therefore gives the best results .
Ammonium Sulphate Ammonium sulphate can be one of the absorbents to remove sulfur in FGD . Saturated ammonium sulphate solution with 10,000 ppm of chloride and pH of 1 at 93˚ C was stimulated by syncrude . Alloy 59 gave the best results . This construction often gives a life of 20 plus years .
Fluoro Chloro Compounds Manufacturing of Fluoro Chloro compounds involves Hydrochloric acid ( HCl )/ Hydrofluoro acid ( HF )/ dichloro methane as by-products . Fluorides and chlorides , which are part of the Halide group , cause severe pitting corrosion , which accelerates further with concentration and temperature . The materials used in operating such conditions need high PREN and Alloy 59 can be used . This material has one of the highest PREN which works well in oxidizing and reducing conditions .
Geothermal Power Plants Geothermal fluids containing dissolved CO 2
, H 2 S , NH 3
, and chloride ions , can cause corrosion of metallic materials . Therefore , the safe utilization of geothermal systems depends on material selection . Corrosion types encountered in geothermal systems include : uniform corrosion , pitting
Table 4 : Thermal Stability properties can be measured by completing the ASTM G28A & G28B tests after sensitizing the material at 871 ° C . Alloy C276 , 22 Heavy pitting attack due to intergranular attack . Alloy 59 has no attacks .
Media |
N10276 |
N06022 |
59 |
ASTM G28A |
> 500 |
> 500 |
40 |
ASTM G28B > 500 339 4 Pitting attack severe severe none Intergranular attack severe severe none
corrosion , sulfide stress corrosion cracking ( SSC ), hydrogen embrittlement , and erosion corrosion . For high temperature geothermal fluids , it is suitable to use Ni-Cr-Mo alloys as a material . Alloy 59 , having very similar Mo content to UNS N06022 , has also shown outstanding pitting corrosion resistance in highly saline geothermal environments of near-neutral pH at 150˚ C . By having high amounts of Molybdenum in the alloy , the influence of temperature on pit nucleation and repassivation can be significantly reduced .
Welding Low carbon and silicon content mean good weldability without susceptibility to hot cracking . Weld consumables in Alloy 59 have extra low carbon . High nickel filler metal with Chromium and Molybdenum can be used for MIG , TIG , or plasma arc welding to itself or other nickel-based alloys . Alloy 59 weld overlay has proven to be effective in other Cr-Ni-Mo alloys , Alloy 625 , and even super austenitic alloys such as 6 Moly . This holds a low sensitivity to hot cracking . Alloy 59 has the lowest corrosion rates in weld zones tested with high chlorides and low pH , compared to N10276 / N06022 .
In Conclusion Alloy 59 is quite versatile material as it can be used in oxidizing and reducing conditions . One of the purest Cr-Ni- Mo alloys has a minimum of unwanted alloying elements which makes it have excellent corrosion resistance . Alloy 59 also has good weldability features and can be used as an option to other Cr-Ni / Mo , C-Grades . It is also available in other forms such as plates / scheduled pipes , large OD pipes , fittings , flanges , and more .
42 Heat Exchanger World February 2024 www . heat-exchanger-world . com