# black oxide

idiom

Source: https://englishreference.com/idiom/black-oxide
Updated: 2026-08-10

## Meaning

Any of several coatings for steels or copper; some are oxides (mainly iron(II,III) oxide), some are nitrites or nitrates, and some are selenides; all are black; the main purposes are the antireflective and cosmetic effects; the anticorrosion effects are small.

## Examples

- The factory uses black oxide to coat the metal parts.
- He applied a layer of black oxide to the steel screws to reduce glare and improve their appearance.
- Engineers often specify a black oxide finish for precision components, prioritizing its antireflective properties over its limited ability to prevent long-term corrosion.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.