Some Notes on Alclad Available to Purchase

DURING the past few years attention has been concentrated on the effect of corrosion on light alloys as measured by the mechanical properties (strength and elongation), rather than by the loss or gain in weight. The most serious type of corrosion, intergranular penetration, causes relatively little change in weight, but a pronounced loss in ductility appears at an early stage and is followed by a loss of strength. The corroding medium most generally used in laboratories is a fine mist from a 20 per cent salt solution. Work has also been in progress on other methods of accelerating corrosion such as repeated immersion in various solutions. A particularly active medium is a 6 per cent salt solution containing 10 per cent by volume of commercial 3 per cent hydrogen peroxide. This solution seems to be very useful in determining whether or not an alloy is susceptible to intergranular penetration. A period of 48 hours in this test appears to have a corrosive action equivalent to from 8 to 12 weeks in the salt spray tank.