In our previous report, we stated as follows:
Inhibitors-filmed catalyst can stop the hydrogenation reaction, while inhibitor film is on the metallic surface. However, catalyst regains its activity as soon as the film is desorbed from the catalyst.
In this report, we have studied about adsorption and desorption temperature of high molecular weight mercaptans. We tried to make a film on the surface of the Cu (R) catalyst with cetyl mercaptan. It was found difficult to film the catalyst in water only by adding the mercaptan in it. As the mercaptan may associate with hydrogen bonding, it can not be adsorbed on the metal surface. Mercaptan can be adsorbed on the catalyst only when the metal is dipped in water in which mercaptan is dispersed at over 85°C, or, in warmed dioxane in which the association of mercaptan is released. As the mercaptan film departs from catalyst surface at 240°-280°C, catalyst revives its activity and the reaction can proceed, giving different products from non-filmed catalytic reaction. So, we can know the film character by analyzing the reaction products.

View full abstract

Dewpoint corrosion of air-heater tubes on marine boilers was investigated, with corrosion-resistant steel tubes intruded, on some ships. The following results were obtained in the test.
1) The tubes failed by corrosion amounted to 20-30% of the whole tubes at the air heater on one ship, and 25-30% on another.
2) Mean corrosion rate of lead-coated tubes is about one half of that of carbon steel tubes, but some lead-coated tubes were perforated by corrosion after six months.
3) Corrosion-resistant steel tubes of Cor-Ten series were much better than the two above, and were not perforated by corrosion even after two years.

View full abstract

For the purpose of obtaining performance data on zinc anode for use in cathodic protection of salt-manufacturing apparatus, laboratory works were carried out.
Anodic potentials and current efficiencies on zinc of various purity and some kinds of zinc alloys were determined in boiling brines at constant current densities ranging from 5 to 30mA/cm². The results and conclusions obtained are as follows:
(1) The tendency for zinc anode to become passive, which is liable to occur in sea-water at ordinary temperature or in fresh water at elevated temperatures, is not observed for zinc except for that of low purity.
(2) Both high-purity zinc and all zinc alloys keep for a long time an anodic potential of -1.0 volt (SCE) and exhibit such a high current efficiency of 90-99%.
(3) Zinc alloys tested show an anode performance of same level as compared with that of high-purity zinc. However, Zn-Al alloys have a tendency to become brittle in hot brine.
(4) In the case of a concentrated brine, in which some salts might deposit to zinc surfaces, the increase in anodic potential of zinc may occur at a lower current density such as 5mA/cm².
(5) For the cathodic protection of salt-manufacturing apparatus, high-purity zinc should be used at higher current densities more than 10mA/cm².

View full abstract