Tomato Acid

[Ryan D 0]

Hello all,

This is my second knife so take it easy on me as this may be a stupid question. i searched the site but didn't find any topic related.

i cut a tomato and let the acid sit on the knife for about 30 mins and small 'marks' appeared. My first knife didn't have this issue. the only difference between the first and second is i tempered the second knife at 375 for 1.5 hours. You can see the marks in the picture. 

So, would a temper have anything to do with a knife being susceptible to rust / acids?   

 

thanks in advance for any incite! 

[Brian Dougherty 1,163]

I wouldn't think any reasonable temper level would drastically change how fast the acid etched the steel.  What temperature was the first one tempered at?

I would expect tomato juice to etch any non stainless steel  blade within a few minutes, so the real question in my mind is why you didn't see this before.  Things that may slow down the oxidation would be a good layer of patina or oxidation already there, a coating of oil or wax on the blade, and maybe the level of polish on the balde.

Tomatoes will vary in acidity as well.  Maybe the earlier ones were low in acid. 

[Ryan D 0]

thanks for the reply -

The first knife was not tempered. And I started thinking about my statement and reran the test on the first knife. i took longer but the etching was visible after an hour. 

and thanks for the suggestions on how to prevent. 

[Brian Dougherty 1,163]

Was the first knife hardened?  (ie quenched)  There is a difference in etching from hardened vs unhardened steel.