WCN Autumn 2010

Zn

Zn5Al

62 days

2 weeks

Figure 12 ▲ ▲ : 1x, 2x and 3x wrapping tests for 3.4mm 1083 ACSR core wires after 185 days at 190°C

Zn

Zn5Al

121 days

4 weeks

Under these conditions, small ruptures begin to appear in the Zn coating. No ruptures are seen in the Zn5Al coating, but a ‘crosshatch-like’ texture begins to appear on the Zn5Al coating which is believed not to be due to coating failure, but is believed to be due to brittleness in an oxidized Zn-Al ‘skin’ developed on the coating during the high temperatures. Figure 14 ▲ ▲ : 1x wrapping tests for 1.85mm Zn-coated 1005 wire after 62 and 121 days at 185°C

Figure 15 ▲ ▲ : 1x wrapping tests for 225°C 3.4mm 1083 conditions, 2 magnifications

Figure 13 ▲ ▲ : 1x wrapping tests for 1.85mm 1005 wires after 185 days at 190°C

due to its lower carbon content, which enhanced diffusion of iron and zinc. Besides carbon, other alloying elements could have an influence on diffusion and consequently temperature resistance time. Wrapping Tests Figure 12 shows wrapping tests of the 3.4mm Zn and Zn5Al coated 1083 core wires taken from the ACSR cable segments after 185 days at 190°C. These tests were done by wrapping the wire around mandrels having 1, 2 and 3x the wire diameter. At this and at all lower time durations, no coating failures were seen in any of the Zn or Bezinalized core wires. For the 1.85mm 1005 wires, failures were noticeable in the case of the Zn coated wire, but not with the Zn5Al coated wire ( Figure 13 ). The Zn coated 1.85mm 1005 wire can be seen to become progressively worse with time at 190°C as shown in Figure 14 . At higher temperatures, defects in coatings on the 3.4mm wires from 1x wrapping tests are noticeable, starting at 225°C after 14 days as shown in Figure 15 . Similar defects were seen with 3x wrapping conditions.

Similar wrappings for 3.4mm 1083 after 28 days at 225°C show no significant differences from those exposed for 14 days at the same temperature. Figure 16 shows 1x wrappings for the 1.85mm Zn and Zn5Al coatings after two and four weeks at 225°C. No damage is seen for either coating after two weeks, but the Zn coating clearly Figure 17 ▼ ▼ : 1x wrappings of 3.4mm 1083 wires after 245°C, 14 days with and without aluminium conductors

Figure 16 ▼ ▼ : 1x wrappings of 1.85mm trials at 225°C, two and four weeks, at two magnifications

Zn with Al conductors

Zn

2 weeks

Zn5Al

Zn without Al conductors

2 weeks

Zn5Al with Al conductors

Zn

4 weeks

Zn5Al without Al conductors

Zn5Al

4 weeks

28

WCN Issue N° 43 www.iwma.org