Feature: New Aluminum Marine Alloy Specification Developed
The Aluminum Association, Inc. The recent publication of the new specification - ASTM B928 High Magnesium Aluminum-Alloy Sheet & Plate for Marine Service - is the culmination of a cooperative effort between numerous parties involved in the marine industry including aluminum producers, boat builders, the Coast Guard and marine classification societies. The combined work of these groups will help to address the communication gap between marine end users and distributors of aluminum that became apparent in late 2001/early 2002 in the Pacific Northwest. As has been reported in various marine industry publications, the performance of some…
Feature: Aluminum Boats Prove Their Mettle
Technology, The Aluminum Association, Inc. Aluminum has been used in the marine industry for more than 100 years because of its light weight and ease of fabrication combined with good corrosion and fatigue resistance. However, for much of the past 30 years, fiberglass has been the material of choice of North American boatbuilders, particularly for higher-volume production lines. Competitively priced compared with boats made from most other materials, fiberglass boats can also be made from standardized molds that reduce their construction time and labor. Aluminum alloys, which are specified for marine use, offer many benefits, though, too.
Aluminum Gone "Bad"
There has been a lot of discussion in the marine industry over the past year with regard to "bad" aluminum. To briefly recap, a number of boat builders purchased aluminum from a supplier that met the requirements of ASTM 5083 H321. This alloy is accepted by both Lloyds Register (Lloyds) and Det Norske Veritas (DNV) for building aluminum vessels. After the aluminum was used to construct some vessels, the operators began to observe surface pitting corrosion. Upon investigation, it was discovered that the purchased plate had been treated differently during manufacturing, with the result that manganese nodules were precipitating out of the alloy, thus making it susceptible to inter-granular corrosion. The result was that newly-built vessels had to be rebuilt and their original hulls scrapped.
