Factors Affecting the Relative Potentials of Tin and Iron¹

Abstract

A previous paper2 we reported data which show that in such electrolytes as canned fruits tin may be less noble than the steel base plate used in making tin plate.Subsequently, similar results were reported by Lueck and Blair3 and by Culpepper and Moon.4 We pointed out that this relationship of the two metals explains many observations in connection with the corrosion in canned fruits which were unexplainable by the commonly held view that tin is the more noble. While reporting our results we had data that indicated some of the reasons for this relationship of tin and iron. In the present paper we submit data which probably indicate the most influential factors in determining the relative single potentials of tin and iron in various electrolytes. In the meantime, however, several views have been published which are so at variance with our data that a brief résumé is deemed advisable. Review of LiteratureLueck and Blair5 state that when tin and iron electrodes are first introduced into electrolytes such as fruit juice, immediately after contact "tin and iron exhibit their normal electrochemical relations-i. e., iron is the anodic metal. However, this condition is quickly reversed and the iron ceases to be corroded at an appreciable rate. This reversal of the polarity in the tin-iron cell under suitable conditions is the direct result of the large difference in the hydrogen overvoltage on the two metals." As we have already pointed out6 the high overvoltage on tin no doubt is an influential factor in determining the extent of corrosion wherever tin is involved as the cathode. Cathodic overvoltage in simple acid media is the result of hydrogen deposition. As long as the tin remains the cathode, the hydrogen overvoltage is an impediment to the progress of corrosion. It is conceivable that, when tin is in the beginning only mildly cathodic, the overvoltage on the cathode may temporarily cause a reversal of the current, particularly if the potential of the iron electrode should happen to fluctuate in a favor-1

EXPLORATORY EXPERIMENTS TO IDENTIFY CHEMICAL REACTIONS CAUSING FLAVOR DETERIORATION DURING STORAGE OF CANNED ORANGE JUICE. I. INCOMPATIBILITY OF PEEL‐OIL CONSTITUENTS WITII THE ACID JUICEa

“…Changes in a canned limonene-citrate system, with and without o~y -gen. The technic adopted for obtaining the oxygen-free lot of this experiment while establishing the presence in each can of a known amount of limonene, made use of the known fact that an acid product during heating in an unenameled can rapidly becomes so highly reduced that a condition of hydrogen overvoltage exists a t the acid-metal interface (14,17).…”

Effect of Sn on the Pitting Corrosion Behavior of Ultra‐Purified 17% Cr Ferritic Stainless Steel

“…The corrosion behavior of Sn‐containing steels in 6 wt% FeCl 3 can be attributed to improved thermodynamic stability of alloying systems by Sn addition and corrosion inhibitor Sn 2+ . Researchers have found that small amounts of dissolved Sn 2+ can play the role in inhibiting the corrosion of Fe in fruit acids . Morad reported that Sn 2+ is the most effective additive among Zn 2+ , N ‐acetylcystein, and S ‐benzylcystein to decrease the corrosion rate of mild steel in 1M H 2 SO 4 solution.…”

Über den Einfluß des Sauerstoffes auf die Korrosion in Dosenkonserven aus Weißblech

“…In allen Versuchen, die in geriihrtem Zitratpuffer durchgefuhrt wurden, stellte sich das Zinnpotential negativer ein als das des Eisens, da das Eisenpotential durch die in Losung gehenden Zinnionen sofort in positiver Richtung verschoben wurde (vgl. 10,11,14). Bei den Messungen in ungeruhrtem Elektrolyten war dies nicht immer der Fall.…”

“…Aufgeloste Zinnionen konnen also sofort an der Eisenoberflache adsorbiert werden und verhindern so auch bei Sauerstoffanwesenheit den wegen der Perforationsgefahr gefahrlichen Lochfrafi (Abb. 10).…”