Studi Komparasi Inhibitor Korosi Imidazoline dan Ethoxylated Fatty Amine (EFA) untuk Pengendalian Korosi Pipa Baja Las Spiral API 5L X-52 dalam Larutan 0,1 M NaHCO3
FERI WIJANARKO, Prof. Ir. Mochammad Noer Ilman, S.T., M.Sc., Ph.D., IPM., ASEAN Eng.
2022 | Tesis | S2 Teknik Mesin
Teknik
pengelasan busur terendam atau submerged arc welding (SAW) banyak
digunakan dalam pembuatan pipa minyak dan gas. Secara umum, sambungan las busur
terdiri atas logam las, daerah terpengaruh panas atau heat affected zone
(HAZ) dan logam induk. Penelitian ini bertujuan untuk mempelajari perilaku
struktur mikro, kekerasan, ketangguhan impak, kekuatan tarik dan laju korosi sambungan las SAW beserta
pengendaliannya melalui penambahan inhibitor organik.
Pada
penelitian ini, pipa spiral dari baja API 5L X-52 dilas dengan las SAW.
Parameter las yaitu arus (I), tegangan (E) dan kecepatan las masing-masing
sebesar 825 Amper, 35 Volt dan 7,5 mm/s. Pengujian korosi dilakukan
dalam larutan 0,1 M NaHCO3 dengan penambahan inhibitor imidazoline
dan ethoxylated fatty amine (EFA) dengan variasi konsentrasi dari 0
sampai 100 ppm. Metode pengujian korosi yang dipakai berupa teknik polarisasi
elektrokimia Tafel dan electrochemical
impedance spectroscopy (EIS).
Hasil penelitian
menunjukkan bahwa struktur mikro logam las terdiri dari ferit asikular dan
ferit batas butir, daerah HAZ terdiri atas struktur bainit, ferit dan perlit,
sedangkan pada logam induk terdiri dari ferit dan perlit. Logam las memiliki
nilai kekerasan paling tinggi, kemudian menurun pada bagian HAZ hingga hingga
mencapai nilai konstan pada logam induk. Kekuatan tarik logam las lebih tinggi
dibandingkan dengan logam induk karena terbentuknya struktur mikro ferit
asikular namun logam las memiliki nilai impak paling rendah dibanding bagian
HAZ dan logam induk. Bagian HAZ memiliki laju korosi paling tinggi dibandingkan
logam las dan logam induk. Penambahan inhibitor imidazoline dan EFA
memberikan penurunan laju korosi dari daerah HAZ. Inhibitor imidazoline memiliki
efisiensi lebih tinggi dibandingkan inhibitor EFA.
Submerged
Arc Welding (SAW) is widely used in the manufacture of oil and gas pipelines.
In general, a weld joint consists of various regions including weld metal, heat
affected zone (HAZ) and base metal. This
research is aimed to study microstructure, hardness, impact toughness, tensile
strength and corrosion rate of submerged arc welded joints with its control
using organic inhibitors.
In this
research, API 5L X-52 steel pipe was welded spirally using SAW technique.
Welding parameters used including welding current (I), arc voltage (E) and
welding speed were 825 Ampere and 35 Volt and 7,5 mm/s respectively. Corrosion
testing was carried out in 0,1 M NaHCO3 solution with the addition
of imidazoline and ethoxylated fatty amine (EFA) corrosion inhibitors. The
methods used included Tafel electrochemical polarization and electrochemical impedance spectroscopy
(EIS).
The results show that
microstructure of the weld metal consists of acicular ferrite and grain
boundary ferrite. On the other hand, the HAZ region is composed of a mixture of
bainite, ferrite and pearlite structures, whilst the base metal consists of
ferrite and pearlite. The weld metal has the highest value of hardness, then
the hardness continuously decreases in the HAZ until it achieves a constant
value in the base metal. The tensile strength of the weld metal is higher than
that of the base metal due to its fine grained acicular ferrite but its impact
toughness is lower compared to that of HAZ and base metal. HAZ region has
highest corrosion rate compared to weld metal and base metal. The additions of both
imidazoline and EFA corrosion inhibitor provided a decrease in the corrosion
rate of HAZ. However, in comparison with EFA inhibitor, imidazoline seems to
have better inhibition efficiency.
Kata Kunci : API 5L X-52, welding, mechanical properties, corrosion, corrosion inhibitor
