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Last time there was a discussion about using dishwashers to wash stainless steel knives, one of the opinions was that the new efficient dishwashers, with dedicated cutlery trays are safe for the knives.
Last year I've picked up dishwasher like that, although never used it to wash my knives. At some point I remembered the discussion and decided to test the Wusthof classic series, flexible boning knife which was given to me. The knife is made of X50CrMoV15 stainless steel, which is stamped on its side. Spec hardness is 54-56HRC.
Test conditions: Dishwasher - Miele Diamante Plus, which is quite hitech, uses less detergent and energy that more common dishwashers. In other words, that means less time and chemicals reacting with the knife blade.
Test started on 05/14/10, Friday. Since then, except for the first short week, I run dishwasher twice a week, currently, the dishwasher gets filled up sufficiently enough to run the washing cycle about twice a week.
The only exception was the last cycle, when the dishwasher was run inthe Pots And Pans mode. I'm being specific about the modes, since the mode selection affects the length of the cycle and in pots and pans more water is hotter, more detergent, in other words chemicals are used. For all cycles, standard dishwasher dry procedure was \used. After the dishwasher completed the dry cycle, it was left open for several hours, and whenever I unloaded it, the knife was removed and placed in the knife block.
Side 1 before test. Side 2 before test.
I'll skip the detailed test log, which isn't too long for now, but nothing has happened during first 4 cycles, after the fifth cycle, I noticed blackish discoloration on the both sides of the blade in the middle.
After 6th cycle, which was last Wed. 06/02/10, I found a rust spot on the blade. Discoloration is also darker. Unfortunately, I was unable to take a good shot of the discoloration, it's visible on the photos, but much more pronounced on a knife.
To be fair, the rust spot appeared on a section that was slightly dented. I am not sure how would that affect the corrosion resistance of the steel, it's not plated as far as I am concerned.
Use concerns - Used knives resist corrosion better. So, in that regard test knife was at a disadvantage, however, considering how 90% or more people use their kitchen knives, sitting them wet or dirty for hours, this one had it easy, never had any time like that.
Still, rust on just 6th cycle was a surprise to me. I was expecting rust, but much later.
For the record, the blade was sitting in the knife block for few months before the test, zero rust or discoloration.
I'll watch how the rust develops for next few weeks, then I'll see what I can change.
Complete article with detailed log - Stainless Steel Knives In A Dishwasher
Last year I've picked up dishwasher like that, although never used it to wash my knives. At some point I remembered the discussion and decided to test the Wusthof classic series, flexible boning knife which was given to me. The knife is made of X50CrMoV15 stainless steel, which is stamped on its side. Spec hardness is 54-56HRC.
Test conditions: Dishwasher - Miele Diamante Plus, which is quite hitech, uses less detergent and energy that more common dishwashers. In other words, that means less time and chemicals reacting with the knife blade.Test started on 05/14/10, Friday. Since then, except for the first short week, I run dishwasher twice a week, currently, the dishwasher gets filled up sufficiently enough to run the washing cycle about twice a week.
The only exception was the last cycle, when the dishwasher was run inthe Pots And Pans mode. I'm being specific about the modes, since the mode selection affects the length of the cycle and in pots and pans more water is hotter, more detergent, in other words chemicals are used. For all cycles, standard dishwasher dry procedure was \used. After the dishwasher completed the dry cycle, it was left open for several hours, and whenever I unloaded it, the knife was removed and placed in the knife block.
Side 1 before test. Side 2 before test.
I'll skip the detailed test log, which isn't too long for now, but nothing has happened during first 4 cycles, after the fifth cycle, I noticed blackish discoloration on the both sides of the blade in the middle.
After 6th cycle, which was last Wed. 06/02/10, I found a rust spot on the blade. Discoloration is also darker. Unfortunately, I was unable to take a good shot of the discoloration, it's visible on the photos, but much more pronounced on a knife.
To be fair, the rust spot appeared on a section that was slightly dented. I am not sure how would that affect the corrosion resistance of the steel, it's not plated as far as I am concerned.
Use concerns - Used knives resist corrosion better. So, in that regard test knife was at a disadvantage, however, considering how 90% or more people use their kitchen knives, sitting them wet or dirty for hours, this one had it easy, never had any time like that.
Still, rust on just 6th cycle was a surprise to me. I was expecting rust, but much later.
For the record, the blade was sitting in the knife block for few months before the test, zero rust or discoloration.
I'll watch how the rust develops for next few weeks, then I'll see what I can change.
Complete article with detailed log - Stainless Steel Knives In A Dishwasher
I was simply referring to spec variation magnitude, I'm not that good in even basic metallurgy to know details at that level. Well, I do know that part now.