Studi sifat ketahanan korosi sumuran baja tahan karat super dupleks SAF 2007 (UNS 32750) u-tube heat exchanger dalam lingkungan air laut pada temperatur 50°C, 55°C, 60°C, 65°C dengan metode polarisasi potentiodynamic = Study of pitting corrosion resilience super dupleks stainless steel SAF 2507 (UNS 32750) U-tube heat exchanger in sea water environment at temperature 50 °C, 55 °C, 60 °C and 65 °C with polarization potentiodynamic method