The influence of frequency of alternating or infrequently reversed current on electrolytic corrosion

Abstract

This paper describes experimental work done to determine the co-efficient of corrosion of iron and lead in soil with varying frequencies of alternating or reversed current with 60 cycles per second as the highest frequency and a two-week period as lowestsome d-c. tests being made as a check on the methods. The results show (1), that a decrease of corrosion occurs with an in crease in frequency; (2), that the corrosion is practically negligible below a five-minute period; (3), that there is, a limiting frequency above which practically no corrosion occurs; (4), that certain chemicals affect the natural and electrolytic corrosion of the two •metals quite differently; (5), that the loss of lead in soil on direct current is about 25 per cent of the theoretical loss; and (6), that alternating or reversed current with as long periods as a day or a week would in the case of iron materially reduce the damage to underground structures. The importance of these results grows out of the fact that there are large areas in practically every city in which the polarity of the underground pipes reverses with periods ranging from a few seconds to an hour or more due to the shifting of railway loads. The investigation shows that the corrosion under such conditions is much less than has generally been supposed.

Effect of pH value on corrosion of carbon steel under an applied alternating current

“…As has been discussed , not all Fe 2+ generated in the anodic cycle of AC are deposited back to Fe substrate in the cathodic cycle. Some are oxidized into Fe 3+ , and then followed by the formation of insoluble iron hydroxide, i.e., Fe(OH) 3 .…”

“…Alternating current (AC) corrosion of buried metallic pipelines has attracted much attention in recent decades. The early work on this topic was mainly concentrated on the factors that affected AC corrosion rate, the mechanisms by which AC induced corrosion occurs, the mitigation methods , as well as the detecting techniques in the case of no cathodic protection (CP). In recent years, more and more research has been conducted to investigate AC corrosion of buried metallic pipelines when CP is applied.…”

Effect of AC current on corrosion behavior of cathodically protected Q235 steel

“…Unfortunately, the mechanism of AC corrosion has not reached a consensus so far and many different theories have been proposed to explain the mechanism of AC corrosion. According to McCollum et al's report , carbon steel will periodically experience cathodic and anodic polarization due to AC current. A net Faraday current will be rectified for the asymmetry of cathodic and anodic polarization, and thereby the “rectification” mechanism is developed.…”