SG2 vs ZDP-189: which Japanese knife steel should you actually buy?

SG2 is the goldilocks of high-performance cutlery steels — keen enough, tough enough, genuinely stainless, and easy enough to live with that you will actually enjoy owning it. ZDP-189 is the opposite kind of steel: brittle at the hardness it is run, a beast to sharpen, and it reacts more than its chromium number suggests. We have carried both. If you are choosing, buy the SG2 — and I say that as someone who does not even own a ZDP-189 knife.

Side by side across the four jobs that matter, these two steels could not be more different in temperament. On edge retention, Knife Steel Nerds' CATRA test put ZDP-189 at about 162% of 440C, a figure published for ZDP-189 itself. But SG2 takes the other three: it is tougher, more corrosion-resistant, and far easier to sharpen. The bars below show the shape of it.

Here is the honest part: the spec sheet oversells ZDP-189 for most kitchens. On paper it is a ~3% carbon monster run to 65 HRC or more with roughly 30% carbide by volume — numbers that scream 'super steel.' And Knife Steel Nerds' CATRA test put it at about 162% of 440C, ZDP-189's own published figure. But edge retention is only worth what you can actually use, and ZDP-189 asks for a level of sharpening skill and board discipline most home cooks do not have and do not want.

SG2, run at 62-64 HRC, hands you a knife you can sharpen on a weeknight and not think about. For the way most people actually cook, that trade is the whole ballgame.

As always, it was never only about the steel. Heat-treat and grind decide more about how a knife cuts than the grade on the box — and ZDP-189 is unusually sensitive to both. Run a touch too hard, ground a touch too thin, and it chips; run well, by a maker who knows it, and it earns its reputation — though it still demands respect. SG2 is far more forgiving of the maker, and of you.

So read hardness as a clue, not a verdict. HRC is the Rockwell number: higher means the steel resists denting and holds a crisp apex longer, but also that it is less forgiving and harder to sharpen. ZDP-189's maker-published floor of 65 HRC or more is near the top of what is sane in a kitchen knife; SG2's 61 to 65 HRC sits in the sweet spot where keen still meets livable.

There are two kinds of sharp, and this pair is the cleanest illustration of it in our whole range. SG2's edge is keen and clean — its fine vanadium carbides take a refined apex that push-cuts beautifully through an onion or the skin of a tomato. ZDP-189's edge is toothy: its much larger volume of coarse chromium carbide gives a micro-serrated bite that grips and saws through fibrous material, and keeps gripping long after a finer edge would have gone smooth.

Neither is 'sharper' in any absolute sense. SG2 is the keen push-cutter; ZDP-189 is the toothy, long-lasting saw. Which you want depends entirely on what — and how much — you cut.

The carbide story is where these two steels really part ways, and it is the honest explanation for everything above. Carbides are the hard particles locked in the steel that do the actual wearing; how much you have, how big they are, and what they are made of together set edge retention, toughness, and how the edge feels. By Knife Steel Nerds' numbers, SG2 carries about 16.5% carbide by volume (point-counted), while Larrin Thomas's Thermo-Calc estimate puts ZDP-189 around 30% — close to double. The two figures come from different methods, but both are his, and the gap is real.

But it is not just more — it is a different kind. SG2's carbide is a fine, even powder-metallurgy mix of chromium-carbide plus a small fraction of very hard vanadium-carbide. ZDP-189's is overwhelmingly chromium-carbide, and there is so much of it that the particles run larger and coarser. That coarse, abundant carbide is exactly what gives ZDP-189 its toothy, long-lasting grip — and exactly what makes it brittle and a nightmare on a stone. More carbide is not simply 'better'; it is a trade, and SG2 sits on the side of that trade most cooks should want. The bars and the schematic below break it down.

Plot both on the map metallurgists use — hardness against toughness, with the rest of the field around them — and ZDP-189 lands in a lonely corner: very hard, and notably low on toughness. SG2 sits where most fine Japanese kitchen steels live: hard enough to hold a keen edge, tough enough to survive a real kitchen. The distance between them is not a step; on toughness it is a chasm. That picture, more than any single spec, is why we steer almost everyone to SG2.

Sharpening day is where my own bias shows, so I will be blunt: I do not own a ZDP-189 knife, and I avoid sharpening one whenever I can. It is that demanding. The same coarse chromium-carbide that makes the edge last makes it fight the stone — it wants diamond plates, it is slow to raise a burr, and it gives weird, vague feedback on most waterstones, so you are never quite sure you have got it. Run it to a true 66-67 HRC and one careless pass can chip the apex you just spent twenty minutes chasing.

SG2 is harder than a basic stainless like VG-10, no question — it rewards a decent diamond or ceramic stone and a little technique. But it responds, it tells you what it is doing, and a patient home cook can absolutely keep it sharp. If ZDP-189's sharpening sounds like a chore, that is because it is one — and it is why, if you would rather not, K&S sharpens and re-profiles both steels in-store.

The chipping question all but decides this one. ZDP-189 is run to 65 HRC or more — often right at the top, 66-67 — and with about 30% coarse carbide it is genuinely brittle. It does not forgive a chicken bone, a frozen edge, a hard cutting board, or a careless twist; chefs who run it accept the occasional chip as the cost of the edge. SG2, tougher to begin with and run a notch softer at 62-64 HRC, is far more relaxed — still a thin Japanese edge, still no pry bar, but much less likely to surprise you.

If you, or your kitchen, are at all heavy-handed, that settles it: SG2. ZDP-189 belongs with a cook who already treats knives gently and knows exactly what they are holding.

Now the myth worth busting, because the spec sheet is genuinely misleading here. ZDP-189 lists around 20% chromium — higher than SG2's ~14-15% — and people read that as 'more stainless.' It is not. ZDP-189's roughly 3% carbon is so high that it pulls most of that chromium out of the steel and locks it into chromium-carbides. Only the chromium left dissolved in the matrix actually resists rust, and there is not much: Larrin Thomas's Thermo-Calc estimate puts it near 6.5%, and in his water-spray test ZDP-189 rusted within eight hours while SG2 and VG10 stayed clean. SG2's chromium mostly stays where it counts.

So in real-world use SG2 is the more corrosion-resistant of the two, and ZDP-189 will spot and react more readily than its big number suggests — fine with normal care and prompt drying, but not the fortress '20%' implies. As I put it to customers: ZDP-189 is really just stainLESS, not stainPROOF. A big chromium number on the label, far less of it actually doing the job.

Living with either comes down to one honest rule: both are sold as stainless, but neither is stain-proof — and ZDP-189 barely clears the bar. SG2's chromium mostly stays free in the steel, so with a rinse and a dry it shrugs off a normal kitchen. ZDP-189, with most of its chromium tied up in carbide, will spot and even lightly rust if you leave it wet, leave acidic food on the edge, or stack it damp — more readily than its 20% chromium number would ever suggest.

The care is simple for both, and matters more for ZDP-189: rinse and dry the blade right after use, never leave it in the sink or the dish rack, keep it dry, and never put either in a dishwasher. And when a ZDP-189 edge finally goes — or chips — bring it to us rather than fighting it on the wrong stone; K&S sharpens and re-profiles both steels in-store.

Written by James Zhang for Knives & Stones. Disclosure: we sell SG2 and carry ZDP-189 when it is in stock — and we still say buy the more forgiving one for almost every kitchen, because that is the honest answer.

Primary sources: Knife Steel Nerds, “VG10 and Super Gold 2” and “ZDP-189 and Cowry-X” by Larrin Thomas. Reviewed June 2026.