The presence of exogenous surface contamination, including dirt, grease, free iron from contact with steel tooling, and so forth, may interfere with the formation of the passive film.

外生的表面污染，包括：尘土、油脂、来自钢铁加工的游离铁等等，可以影响到钝化膜的生成。

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In the course of separation within a three-product HM cyclone, the tangential velocity of particles are slack behind that of heavy medium, leading to contamination of dirt in concentrate;

在无压给料三产品重介质旋流器分选过程中，由于物料的切向速度可能会滞后于重悬浮液的切向速度，致使精煤受矸石污染；

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Hydrophobic coatings seal lens surfaces with an ultra-smooth polymer, making it easy to clean the eyeglass lenses from dirt, water or oily contamination can simply be wiped off.

加硬防水膜在镜片表面封上一层非常致密平滑的聚合物，使得镜片表面灰尘、水及油污清洁异常方便。

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Because farming takes place out of doors and in dirt, such contamination is a fact of life.

FORBES: Bittman of the 'New York Times': Always Out To Lunch