Hot-dip galvanizing immerses the finished panel in molten zinc, producing a thick metallurgically bonded layer that protects the steel both as a barrier and sacrificially. It is the default for anything outdoors and the only sensible answer for a yard trench that spends winter under salted runoff.

It has two costs beyond price. The heat distorts thin or asymmetric sections, so a fine architectural panel may not come back flat, and the surface is rougher and less even than a plated one, which matters where the grating is visible or has to be cleaned frequently.

Electroplated galvanizing deposits a thinner, smoother, more uniform zinc layer at ambient temperature. It suits indoor work and fine sections and does not suit prolonged outdoor exposure, because the layer that makes it smooth also makes it thin.

Acid passivation is not a coating at all but a treatment for stainless. Cutting, welding and forming leave free iron on a stainless surface, and that free iron rusts as if it were carbon steel, which is why a new stainless panel can show rust spots within weeks. Passivation removes it and restores the passive layer.

The practical rule is to state the environment rather than the coating. Tell us that a panel goes in a coastal yard, a food processing floor or a heated lobby, and the coating follows from that.