Ni-resist iron for propellers

Ni-Resist is the name applied to a group of alloy irons to which a sufficient amount of alloying element (mainly nickel) has been added to produce an austenitic matrix. Because of the alloy content and the austenitic matrix, Ni-Resist irons exhibit much better corrosion resistance and toughness than do ordinary cast irons.

A case history on the phenomenal corrosion of marine propellers in fishing boats

Although high tensile brassess of copper-zinc alloys (Manganese bronze) find extensive use in all marine applications, under aggressive sea-water, marine propellers cast out of such an alloy frequently suffer heavy corrosion damages due to dezincification. An interesting case history where a number of propellers have undergone dezincification in the Cochin backwaters is narrated in this paper.

Trawling Operations and South African (Cape) Fur Seals, Arctocephalus pusillus pusillus

South African (Cape) fur seals, Arctocephalus pusillus pusillus, interact with the South African trawl fisheries-offshore demersal, inshore demersal, and midwater fisheries. These interactions take thef ollowing forms: Seals take or damage netted fish, on particular vessels they become caught in the propeller, seals drown in the nets, live seals come aboard and may be killed. Except in specific cases of seals damaging particular trawler propellers, interactions result in little cost to the offshore and midwater trawl fisheries. For the inshore fishery, seals damage fish in the net at an estimated cost in excess of R69, 728 (US$18,827) per year, but this is negligible (0.3%) in terms ofthe value of the fishery. Seal mortality is mainly caused by drowning in trawl nets and ranges from 2,524 to 3,636 seals of both sexes per year. Between 312 and 567 seals are deliberately killed annually, but this most likely takes place only when caught and they enter the area below deck, where they are difficult to remove, and pose a potential threat to crew safety. Overall, seal mortality during trawling operations is negligible (0.4-0.6%) in terms of the feeding population of seals in South Africa.