VELOCITY-ASSISTED VELOCITY-ASSISTED CORROSION OF API X-52 CORROSION OF API X-52

STEEL IN 3. 5 % NaCl STEEL IN 3. 5 % NaCl SOLUTIONSOLUTION

DR. AMARNATH & DR. AMARNATH &

PROF.T. K. G. NAMBOODHIRIPROF.T. K. G. NAMBOODHIRI

DEPT. OF METALLURGICAL DEPT. OF METALLURGICAL ENGINEERING, BANARAS ENGINEERING, BANARAS

HINDU UNIVERSITYHINDU UNIVERSITY

INTRODUCTIONINTRODUCTION

Corrosion of metals in fluids enhanced Corrosion of metals in fluids enhanced by relative velocity of corrodentby relative velocity of corrodent

Corrosion increases with increasing Corrosion increases with increasing velocity, first by mass-transfer and then velocity, first by mass-transfer and then by surface shear forces.- Laminar flow. by surface shear forces.- Laminar flow.

In turbulent systems impingement In turbulent systems impingement attack and cavitation damage lead to attack and cavitation damage lead to increased corrosion. increased corrosion.

EROSION-CORROSION IN EROSION-CORROSION IN AQUEOUS SYSTEMSAQUEOUS SYSTEMS

EROSION-CORROSION

VELOCITY-ASSISTED

CORROSION IMPINGEMENT ATTACK CAVITATION-DAMAGE

EFFECT OF VELOCITY ONEFFECT OF VELOCITY ON MASS LOSS MASS LOSS

VELOCITY- ASSISTED CORROSION UNDER VELOCITY- ASSISTED CORROSION UNDER LAMINAR FLOWLAMINAR FLOW

IMPINGEMENT ATTACK-IMPINGEMENT ATTACK-TURBULENT FLOWTURBULENT FLOW

Under turbulent Under turbulent flow high velocity flow high velocity impact of fluids impact of fluids leads to removal of leads to removal of materialmaterial

Stress created by Stress created by fluid impact crack fluid impact crack or remove corrosion or remove corrosion product films and product films and expose fresh metalexpose fresh metal

CAVITATION DAMAGECAVITATION DAMAGE

Pressure variations Pressure variations in flowing liquids in flowing liquids lead to formation of lead to formation of bubbles or cavities. bubbles or cavities.

Under high Under high pressure, these pressure, these bubbles collapse bubbles collapse violently and violently and damage nearby damage nearby surface. surface.

AIM OF THE PAPERAIM OF THE PAPER

Line-pipe steels like API X-52 are used for Line-pipe steels like API X-52 are used for large diameter pipelines carrying crude, large diameter pipelines carrying crude, natural gas and petroleum products over natural gas and petroleum products over large distances, often under the sea. large distances, often under the sea.

Exposure to high velocity fluids within and Exposure to high velocity fluids within and the dynamic sea-environment outside the dynamic sea-environment outside make these pipelines susceptible to make these pipelines susceptible to erosion-corrosion. erosion-corrosion.

This paper evaluates the erosion-corrosion This paper evaluates the erosion-corrosion behaviour of API X-52 in flowing 3. 5 % behaviour of API X-52 in flowing 3. 5 % NaCl solutionNaCl solution

ExperimentalExperimental

Commercial API X-52 supplied by SAIL R&D, Commercial API X-52 supplied by SAIL R&D, Ranchi as 10 mm thick hot rolled plate. Ranchi as 10 mm thick hot rolled plate. Table 1- chemical compositionTable 1- chemical composition

Strips hot rolled to 2. 5 mm at 850 C. Some Strips hot rolled to 2. 5 mm at 850 C. Some strips cold rolled to 10, 30 and 50 % strips cold rolled to 10, 30 and 50 % reductions. Some strips annealed at 950 C, reductions. Some strips annealed at 950 C, furnace cooled or water quenched and furnace cooled or water quenched and tempered at 150 Ctempered at 150 C

Immersion tests for general corrosion. Immersion tests for general corrosion. Exposure on a parallel disk rotating Exposure on a parallel disk rotating assembly for velocity effects. Weight loss assembly for velocity effects. Weight loss measurements. measurements.

TABLE 1:CHEMICAL COMPOSITION OF TABLE 1:CHEMICAL COMPOSITION OF API X-52 STEEL API X-52 STEEL

Nominal Composition, Weight %Nominal Composition, Weight %

CC MnMn SiSi PP SS NbNb VV FeFe

0. 150. 15 1.251.25 0. 200. 20 0. 0270. 027 0. 0260. 026 0. 040. 04 0. 050. 05 BalaBalancence

PARALLEL DISK ROTORPARALLEL DISK ROTOR

RESULTSRESULTS

Mechanical Properties, Table 2Mechanical Properties, Table 2 MicrostructuresMicrostructures STATIC CORROSION: TABLE 3STATIC CORROSION: TABLE 3 VELOCITY-ASSISTED CORROSIONVELOCITY-ASSISTED CORROSION

Table 3Table 3 Mechanical properties of Mechanical properties of API X-52 steelAPI X-52 steel

conditionsconditions YSYS UTSUTS % el Hardness % el Hardness

(MPa) (MPa) (VPN)(MPa) (MPa) (VPN)

As-received 476As-received 476 595 595 30.0 30.0 180 180 10 % cold rolled10 % cold rolled 580 580 620 620 4.13 4.13 312 312 30 % cold rolled30 % cold rolled 610 610 679 679 2.40 2.40 339 339 50 % cold rolled50 % cold rolled 695 695 765 765 1.06 1.06 363 363 Q & T. 639Q & T. 639 972 972 10.3 10.3 389 389 AnnealedAnnealed 297 297 481 481 31.95 134 31.95 134

MICROSTRUCTURE OF API X-52MICROSTRUCTURE OF API X-52

As-received As-received (hot rolled) (hot rolled) steelsteel

MICROSTRUCTURE OF API X-52MICROSTRUCTURE OF API X-52

AnnealedAnnealed Quenched & Quenched &

temperedtempered

10 % cold rolled10 % cold rolled 30 % cold rolled30 % cold rolled 50 % cold rolled50 % cold rolled

Table 3. Static corrosion of API X-52 steel Table 3. Static corrosion of API X-52 steel 3.5% NaCl, 20 days’ exposure3.5% NaCl, 20 days’ exposure

ConditionsConditions Corrosion Corrosion

Rate, mddRate, mdd Hot rolledHot rolled 20 20 AnnealedAnnealed 23 23 Quenched & temperedQuenched & tempered 13 13 10 % Cold rolled10 % Cold rolled 18 18 30 % Cold rolled30 % Cold rolled 14 14 50 % Cold rolled50 % Cold rolled 19 19

VELOCITY-ASSISTED VELOCITY-ASSISTED CORROSIONCORROSION

API X-52 Steel, as-API X-52 Steel, as-received, 3. 5 % received, 3. 5 % NaClNaCl

Variation of Variation of corrosion rate with corrosion rate with time at three time at three velocitiesvelocities

Corrosion rate Corrosion rate increases with increases with increasing velocityincreasing velocity

VELOCITY ASSISTED VELOCITY ASSISTED CORROSIONCORROSION

Corrosion rate (Hot Corrosion rate (Hot rolled steel) increases rolled steel) increases with increasing with increasing velocity (0. 11 m/s to velocity (0. 11 m/s to 4. 62 m/s)4. 62 m/s)

At velocities above At velocities above 400 RPM(0. 86 m/s), 400 RPM(0. 86 m/s), the corrosion rate was the corrosion rate was found to be more than found to be more than that for a rotating that for a rotating cylinder with laminar cylinder with laminar flow. (Erosion-flow. (Erosion-corrosion)corrosion)

EFFECT OF THERMAL AND EFFECT OF THERMAL AND MECHANICAL TREATMENTSMECHANICAL TREATMENTS

Velocity-assisted Velocity-assisted corrosion changes corrosion changes with thermo with thermo mechanical mechanical treatmentstreatments

Increasing cold Increasing cold work decreases the work decreases the corrosion ratecorrosion rate

Q & T steel shows Q & T steel shows the lowest the lowest corrosion ratecorrosion rate

TABLE 4. EFFECT OF THERMOMECHANICAL TABLE 4. EFFECT OF THERMOMECHANICAL TREARMENTS ON CORROSIONTREARMENTS ON CORROSION

Thermo mechanical Treatment

Corrosion rate, mdd in 3. 5 % NaCl solution

Static24 hrs

Dynamic1. 36 m/s20 hrs.

Annealed 28 5054

Hot rolled 85 932

10 % C. R. 47 832

30 % C. R. 48 793

50% C. R. 70 671

Q & T 42 617

EFFECT OF HARDNESSEFFECT OF HARDNESS

Velocity-assisted Velocity-assisted corrosion corrosion decreases with decreases with increasing increasing hardness of the hardness of the steel. steel.

This dependence This dependence attributed to attributed to impingement impingement attack and/or attack and/or cavitation damage. cavitation damage.

CONCLUSIONSCONCLUSIONS

API X-52 steel undergoes erosion-API X-52 steel undergoes erosion-corrosion in flowing 3. 5 % NaCl corrosion in flowing 3. 5 % NaCl solution. solution.

Increasing velocity increases the Increasing velocity increases the corrosion rate, the increase corrosion rate, the increase dependent on the condition of steel. dependent on the condition of steel.

The dynamic corrosion of the steel The dynamic corrosion of the steel decreases with increasing hardness. decreases with increasing hardness.

LIST OF PUBLICATIONSLIST OF PUBLICATIONS Amarnath, M. M. Singh and T. K. G. Namboodhiri, Corrosion of Amarnath, M. M. Singh and T. K. G. Namboodhiri, Corrosion of

API X-52 grade line pipe steel in sodium chloride media, Trans. API X-52 grade line pipe steel in sodium chloride media, Trans. SAEST, 35 (2000), 85-90SAEST, 35 (2000), 85-90

Amarnath, T. K. G. Namboodhiri and S. N. Upadhyay, Flow Amarnath, T. K. G. Namboodhiri and S. N. Upadhyay, Flow Assisted Corrosion of API X-52 Steel in 3. 5% NaCl Solution, The Assisted Corrosion of API X-52 Steel in 3. 5% NaCl Solution, The Canadian Journal of Chemical Engineering, 80 (2002) (6), 456-Canadian Journal of Chemical Engineering, 80 (2002) (6), 456-464464

Amarnath and T. K. G. Namboodhiri, Effect of cold rolling on the Amarnath and T. K. G. Namboodhiri, Effect of cold rolling on the hydrogen-induced delayed failure of API X-52 line-pipe steel, hydrogen-induced delayed failure of API X-52 line-pipe steel, Trans. Indian Inst. Metals, 55 (2002), 25-30Trans. Indian Inst. Metals, 55 (2002), 25-30

G. Ananta Nagu, Amarnath and T. K. G. Namboodhiri, Effect of G. Ananta Nagu, Amarnath and T. K. G. Namboodhiri, Effect of heat treatments on the hydrogen embrittlement susceptibility of heat treatments on the hydrogen embrittlement susceptibility of API X-65 grade line-pipe steel, Bull. Mater. Sci. ,26 (2003)435-API X-65 grade line-pipe steel, Bull. Mater. Sci. ,26 (2003)435-439439

Amarnath, S. N. Upadhyay and T. K. G. Namboodhiri, Effect of Amarnath, S. N. Upadhyay and T. K. G. Namboodhiri, Effect of thermal and mechanical treatments on corrosion of API X-52 thermal and mechanical treatments on corrosion of API X-52 grade line-pipe steel in flowing 3. 5 % NaCl solution, Indian J. grade line-pipe steel in flowing 3. 5 % NaCl solution, Indian J. Chem. Technol. , 10 (2003) 611-614Chem. Technol. , 10 (2003) 611-614