General corrosion and corrosion under deposits on a tube for an air fin cooler system

Abstract

ABSTRACT

An air fin cooler system consists of a tube bundle that is used to cool the various processing fluids in process industries that utilizes air as a cooling medium. The said tubes failed when exposed to corrosive environment(s). Tubes located at the bottom row of the air fin cooler were corroded as a result of exposure to rain water, brought in by induced air when the wind blows. The tube material is A179 Carbon steel. Two tubes, namely Tube A and Tube B along with an aluminum fin in each tube were investigated. A leak was observed on tube A, probably due to Corrosion Under Deposit mechanism.  A general corrosion attack was observedube B, and macroscopic analysis showed thathe corrosion occurred along the rain boundaries, which consist of ferrite and pearlite. Microanalysis showed that the corrosion product on the outer surface of the tube consists of Fe_, O, S and Cl elements. It is concluded that the humid environment contains corrosive elements such as S and Cl. EDAX analysis on the fin showed that the material is pure aluminum. However, the aluminum was corroded by galvanized corrosion and produced brittle Al₂O₃ as a result. 

ABSTRAK

Sistem pendingin sirip udara mengandungi satu tiub berkas yang ialah digunakan untuk bertenang pelbagai cecair-cecair pemprosesan dalam industri pemprosesan yang menggunakan udara sebagai bahantara pendinginan. Kata tiub-tiub menggagalkan apabila mendedahkan kepada persekitaran mengkakis(s). Tiub-tiub berkedudukan barisan bawah pendingin sirip udara dikakis akibat pendedahan untuk air hujan, dibawa oleh udara teraruh apabila tiupan angin. Bahan tiub ialah keluli karbon A179. Dua tiub, iaitu Tube A and Tube B bersama dengan sirip aluminium dalam setiap tiub telah disiasat. Satu kebocoran telah diperhatikan pada tiub A, mungkin disebabkan mekanisme Corrosion Under Deposit. Serangan kakisan umum telah diperhatikan di tiub B , dan analisis makroskopik menunjukkan yang kakisan berlaku selari ira sempadan-sempadan, yang terdiri daripada ferit dan pearlit. Microanalysis menunjukkan yang produk kakisan pada permukaan luar tiub mengandungi Fe, O, unsur-unsur S and Cl. Diakhiri yang persekitaran yang lembap mengandungi unsur-unsur mengkakis seperti S and Cl. Analisis EDAX pada sirip menunjukkan yang bahan ialah aluminium tulen. Bagaimanapun , aluminium dikakis dengan merangsangkan kakisan dan menghasilkan Al2O3 rapuh hasilnya.