New galvanized metal appears too clean and sometimes shiny -- exactly the opposite of what's suitable for country or rustic decorating projects. Instead of leaving the metal outside for years to age on its own, speed up the process with vinegar or faux-finish it with paint or glaze. Many types of galvanized metal do not rust, but a patina or a duller finish makes them look weathered or aged. If you prefer a rusty look, use paints or glazes to add as much or as little as you like.
A Vinegar Bath
To remove the shiny, new look from galvanized metal, submerge the metal item in a plastic tub or bucket full of white vinegar. Opt for inexpensive bulk white vinegar since it may take quite a bit to cover your project piece. Sit the object in the vinegar at least overnight, flipping it or turning it on its side to submerge other areas if you're unable to submerge the entire piece at once. If the metal object is too large to submerge, such as a flat or corrugated sheet several feet long, rest it flat on a plastic tarp; then spray vinegar over it several times during the day after scuffing up the metal surface a bit with a fine-grit sandpaper. If you'd rather not spray the piece, soak paper towels in vinegar and cover the metal with the wet towels, adding more vinegar as needed when the towels dry out. If the metal still doesn't oxidize, scuff it up a bit with sandpaper; then soak it in the vinegar again.
Remove that brand-new look from your project piece with flat white or gray paint. If your galvanized project piece looks shiny, scuff it up a bit first with a fine-grit sandpaper; then wipe the dust away with a soft cloth. Dip the tip of a paintbrush into flat white or a light gray paint; then wipe most of the paint back off into the paint container or on a paper towel. Dry-brush the white paint over the galvanized metal; then wipe it while still wet with a soft cloth or a wadded-up paper towel. The end result looks weathered but not beat up, as if the metal sat outside for a year or so.
A Touch of Rust
Give galvanized metal a hint of a rusty look using a dark brown glaze or thinned paint. Apply the glaze to areas that may show rust the most on non-galvanized metal, such as in bent and creased areas or along the edges of details. Use a brush with only a small amount of glaze or paint on its bristles to coat the metal; then wipe away most of the color with a paper towel. If mixing a watered-down paint, start with a solution of two parts water, one part paint; if you want it to look darker, add more paint. Add rusty-looking specks to the project by dipping the tips of toothbrush bristles in dark brown or black paint, dragging your thumb across the bristles while holding the brush close to the project. Wear a rubber glove if you don't want paint on your hand.
Distressing the Metal
Make galvanized metal look even more used, abused and neglected by distressing it a bit. Add dents in flat metal by placing a block of wood beneath the metal and resting a few nuts and bolts on the top, hammering the hardware to create dents. Hammer any sharp metal edges on the project -- some galvanized metal pieces can be quite sharp -- then file or sand them smooth. Mix equal parts water and vinegar in a spray bottle, then mix in some salt -- 2 tablespoons per cup should be more than enough. Spray the metal and allow it to sit outside for a few days to add to the aged look. You can also distress the piece before adding paint or glaze.