Umthelela wokuqoqwa kanye nokwedlula ngesikhathi sokwenza kuqala, ukushisela, ukuhlolwa, nokwelashwa kokushisa kuzodala i-iron oxide, i-welding slag, igrisi, nokunye ukungcola kunqwabelene phezu kwepayipi (ipayipi lensimbi ye-carbon, ipayipi le-carbon copper, ipayipi lensimbi engagqwali) , okuzonciphisa ukumelana nokugqwala kwepayipi yensimbi. Izinhlobonhlobo. I-Pickling iyindlela yokukhipha ukugqwala kwamakhemikhali: ukukhishwa kwe-asidi ye-dilute kukhipha ikakhulukazi ama-oxide ensimbi ebusweni bamapayipi ensimbi engagqwali ngomoya-mpilo. Ngensimbi eyinsimbi, ikakhulukazi ibhekisela ku-iron oxide, ehlangana ngamakhemikhali nalawa ma-oxide ensimbi futhi awancibilikise ku-asidi ukuze kuzuzwe inhloso yokukhipha ukugqwala. Ngaphambi kokukhishwa kwe-pickling kanye nokugqwala, amafutha odongeni lwepayipi yensimbi engagqwali kufanele asuswe kuqala, ngoba ukutholakala kwamafutha kuvimbela uketshezi lokuqoqa ukuthi luthinte udonga lwepayipi yensimbi. Ithinta umphumela wokususa ukugqwala. Amapayipi angenawo uwoyela (njengamapayipi ensimbi engagqwali omoya-mpilo) kufanele akhishwe amafutha kuqala. I-Pickling ibhekisela ekusebenziseni izixazululo zokukhetha njenge-sulfuric acid ukugeza ungqimba lwe-oxide nothuli endaweni yokusebenza. I-Phosphating iyindlela yokwelapha yokuhlanza ubuso.