Effects of Phosphoric-Tannic Acids On Rusting Kinetics of Clem and Rusted Low Carbon Steels

In recent years, commercial yducts claiming tn he rust converter hay: b%;r nmketed and reported to msforrn mnpmtcctive types ol iron oxides =id cxyhydrox~des into more protective oxide, Mmt ate pro~riemfo rmulations, but it is geneeral!y knwn that phosphoric and/or un~lica ids are fiequeretly uscd as heir main wnstlluents. Since their imepticlr: nrst convcrrer or rust aansfnrrner performance ha; a l w ~ pb ~un~ d e r smtiny. hh as been done on both phosphoric a ~ dram ic acid as a caPZysz for mt tramformarion. Tannic acid is hlieved by some ro cause the tramfmnation of bptamtivmcy hydroxides into magwrite. So far, few smdiw haw Ezen done on the pertbrmance of the phosphori~tannic =id mixmre which was planned in this sescarch work. The primary obj~dveso f this work were tc study both the mechanisms and degree of pmreaion offered by ezch of fit following wish steel a~rfatles: (1) phosphoric acid, (2) tannic acid, (4) A mixture of phosphoric and rannic acids. (4) A commercial brand rust transformer. Accelerated wmtheaing testing, x-ray diffraction I(X RD), infrared spectroscopy (IR), a d scanning ellectron microtco?y (SEM) were used in this research. Rnulrs of this research indim# that a41 formulations includins the commercial one arc; ineffwtive in reducing thz canwion rate whcn applied an initially cleaned low m b n sml. Initially mstcd low carbon steel samples ueatcd with either phosphoric acid or a mixture or phr~iphurica nd unnic xlds resulted in the l ~ w e s cso rrosion rates (about 3 mpy) when rcsrcd in a sirnularcd weathering chamber.