Production of higher-quality galvanized pipe for land reclamation

Abstract

The Voroshilovgrad Pipe Plant has mastered the production of spiral-welded steel pipes with a zinc coating for farm irrigation. In introducing this technology, the plant investigated the effect of different alloying elements (magnesium, aluminum, nickel, copper) introduced into the zinc melt on the corrosion resistance of the resulting coatings. Accelerated tests were conducted in a 3% aqueous solution of superphosphate and in artificial seawater, as well as in soil wetted varying amounts with seawater. The results showed that zinc coatings simultaneously alloyed with 0.050.15 AI and 0.05-0.3 Ni (wt.%) had the best corrosion resistance. Depending on the medium, the corrosion resistance of these coatings was 1.33-1.54 times greater than that of the unalloyed zinc coatings. 9 The data obtained made it possible to select a composition for the melt to be used in galvanizing pipes. Commercial galvanizing baths were alloyed with nickel by placing plates of nickel about the perimeter of the bath. Pipes were galvanized in the nickel-alloyed baths by the following regime: temperature 450 _+ 5~ time of immersion 25 sec; time of extraction 40 sec. The thickness of the coating was 80 #m, which met the requirements of TU 14-3-1001-81. Thus, it was discovered that microalloying galvanizing baths with micro-additions of other metals can improve the corrosion resistance of the latter. The above-described technology for pipe-galvanizing has been introduced at the Voroshilovgrad plant for galvanizing spiral-welded pipes. The use of pipes with an alloyed zinc coating increases the service life of the irrigation systems in which the pipes are used.