When new pipe is connected to old rusty pipe, generally, the new pipe is anodic to the old pipe.

当新管子和生锈旧管子相连时，新管子相对于旧管子常为阳极。

youdao

If the drill pipe threads become rusty, rust will have to be cleaned.

如果钻杆丝扣生锈，必须清除掉。

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At the end of the pump valves, cast iron pipe and other items to be rusty rust, and then coated with butter, dry place on the preservation, re-use for winter and spring.

水泵的底阀、弯管等铸铁件，生了锈的要除锈，然后再涂上黄油，放在干燥处保存，以备冬春再用。

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Jorge walks past a rusty steel pipe, about half a metre high.

BBC: NEWS | Programmes | From Our Own Correspondent | Mexico's sinking city

Black fume billowed from its exhaust pipe as the rusty machine lumbered to the edge of the crater.

NPR: Excerpt: 'Legends'