# Naval jelly and knife blades

**URL:** <https://boards.straightdope.com/t/naval-jelly-and-knife-blades/562910>\
**Category:** Factual Questions\
**Created:** [December 4, 2010, 5:04am UTC](https://boards.straightdope.com/t/naval-jelly-and-knife-blades/562910 "2010-12-04T05:04:54Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Slow\_Moving\_Vehicle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slow_moving_vehicle/32/291_2.png) [@Slow\_Moving\_Vehicle](https://boards.straightdope.com/u/Slow_Moving_Vehicle)\
**Post date:** [December 4, 2010, 5:04am UTC](https://boards.straightdope.com/t/naval-jelly-and-knife-blades/562910/1 "2010-12-04T05:04:54Z")

</div>

So I just cleaned my year-old Bokker pocketknife’s blades with naval jelly, to remove some rust. It seems to have done so, but now the bright shiny steel is rather dull and dark. This is a high-carbon, rather than stainless, steel.

Have I done any damage to my knife, other than aesthetic?

---

<div class="post-metadata">

**Author:** ![crowmanyclouds](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crowmanyclouds/32/19884_2.png) [@crowmanyclouds](https://boards.straightdope.com/u/crowmanyclouds)\
**Post date:** [December 4, 2010, 5:14am UTC](https://boards.straightdope.com/t/naval-jelly-and-knife-blades/562910/2 "2010-12-04T05:14:04Z")

</div>

> [@](#):
>
> Phosphoric acid may be used as a “rust converter”, by direct application to rusted iron, steel tools, or surfaces. The phosphoric acid converts reddish-brown iron(III) oxide (rust) to black ferric phosphate, FePO4.
> 
> “Rust converter” is sometimes a greenish liquid suitable for dipping (in the same sort of acid bath as is used for pickling metal), but it is more often formulated as a gel, commonly called naval jelly. It is sometimes sold under other names, such as “rust remover” or “rust killer”. As a thick gel, it may be applied to sloping, vertical, or even overhead surfaces.
> 
> After treatment, the black ferric-phosphate coating can be scrubbed off, leaving a fresh metal surface. Multiple applications of phosphoric acid may be required to remove all rust. The black phosphate coating can also be left in place, where it will provide moderate further corrosion resistance. (Such protection is also provided by the superficially similar Parkerizing and blued electrochemical conversion coating processes.)[RIGHT][CITE](http://en.wikipedia.org/wiki/Phosphoric_acid#Rust_removal)[/RIGHT]

CMC fnord!

---

<div class="post-metadata">

**Author:** ![Slow\_Moving\_Vehicle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/slow_moving_vehicle/32/291_2.png) [@Slow\_Moving\_Vehicle](https://boards.straightdope.com/u/Slow_Moving_Vehicle)\
**Post date:** [December 4, 2010, 6:31pm UTC](https://boards.straightdope.com/t/naval-jelly-and-knife-blades/562910/3 "2010-12-04T18:31:58Z")

</div>

> [@crowmanyclouds](#):
>
> CMC fnord!

Thanks, **crowmanyclouds**.