Although manufacturers like to make all sorts of marketing claims about how nitriding surfaces makes them “so much harder”, that is for the most part complete BS.
Yes! It does harden the surface layer of mild steel, but not meaningfully. For example, a 1/4” thick plate of A36 steel may have a Rockwell C hardness of 12 in its normal state. After nitriding, the surface may be in the 46-60HRC range depending on the quality of the treatment. BUT, that hardness only goes to a depth of… wait for it… LITERALLY – 0.0004–0.0012 in.! So imagine laying a super hard Kleenex on the surface of the table. Except that a Kleenex would be 10 times thicker!
So the bottom line is that nitriding only provides a thin crispy shell, like an M&M, which maybe prevents a little surface scratching but does absolutely nothing to protect from impacts.
Nitriding provides some surface corrosion resistance and some scratch resistance. However, the treatment is micro-porous and can crack. So even corrosion resistance is limited unless you add an oxide and a sealant. But you can’t do that on a welding surface! So nitriding will help the surface stain a bit slower, and maybe fingerprint less. But with any trapped moisture, it will damage quickly. It is NOT an anti-corrosion coating. Against corrosion alone, a freshly applied WD-40 film, especially the Specialist Corrosion Inhibitor, can outperform nitriding-only by a wide margin in salt-spray testing, often by an order of magnitude.
Bottom line: if you actively maintain it, WD-40 protection beats nitriding-only for corrosion resistance by a lot. Nitriding still helps with wear and stain resistance, but it is not a corrosion coating. So if it’s not good for corrosion, or for impact, what’s it good for?