Steel and iron are amazing materials. They are used both indoors and out, through all kinds of weather and many different climates. They are strong and durable, non-toxic, and don’t burn or rot except under extreme conditions. Rust and corrosion, however, can slowly eat away at metal over time.
Large pieces of steel and iron can take hundreds of years to rust to a point where it is no longer useful, but smaller pieces can go pretty fast. On occasion rust is part of the decoration for the piece, such as using patinas to intentionally rust an item for coloring. Other times rust is seen as ugly or dirty and detrimental to long term use of an object. This is why almost most metal pieces are treated in some way to prevent and protect against rust and corrosion. Whether it is painted, waxed, or oiled, there are ways to control the corrosion and keep your metal art looking good and clean for generations. A little maintenance goes a long way in most applications, however, having the finish scratched, worn away, or being exposed to different chemicals like cleaning agents can start rust taking over your items.
Types of finishes
Paint is often used and can give the work a bit of decoration as well. You can opt to add color or just use a simple clear coat of enamel to keep the general look of the metal without changing the color much. Paint can be scratched off or removed with chemicals and cleaners, but this type of finish can normally be used both inside and outside and give a pretty sturdy level of protection.
Waxes, like S.C. Johnson’s paste wax or bee’s wax can result in a more traditional look. Applied cold it protects the metal without substantially changing the appearance. If the piece is carefully heated before applying the wax it darkens the metal and allows the protection to penetrate the pores of the metal.
The coating is thinner than painting and scratches can also penetrate the wax coating. This type of finish is normally better used on pieces that are deemed for inside use as pollution can be enough to strip away wax coatings.
Oils, like boiled linseed oil or most cooking oils, can be used to treat indoor items as well. Once again, there is the possibility of scratching through the coating which allows rust to form. Using boiled linseed oil works well for indoor items but shouldn’t be eaten off of. If an item is going to be used to serve food, it is best to use a vegetable oil, and most likely season the piece much like a cast iron pan would be seasoned. Canola or coconut oils are two of my favorites for this purpose.
Powder Coating is yet another way that some metal items are protected. Powder coatings are a type of plastic that is sprayed on as a powder and heated to melt into a protective covering. This is the more expensive type of treatment and is normally used for outdoor applications like railings and benches. Again, if there are scratches through the coating rust can form. Well used rails and other architectural items might need a bit of work every decade to make sure the coating is holding up with no cracking or peeling. Powder coating is most likely the most durable, but the costliest method of protecting steel and iron. It is also the hardest for a person to maintain or repair themselves.
Oh no, rust has invaded. Now what?
Rust has to progress quite a bit before things are not fixable. A little work can have your piece almost good as new in most cases. A little elbow grease and a few basic tools can get you back on track. Since most of my work is painted, I will focus on that next
- Scrub the loose rust and paint free using a steel wire brush
- File any areas that have rusted. On flat surfaces you may use a coarse file and any rounded surfaces sandpaper (80 grit) will normally clean the area well.
- Neutralize – Any exposed areas of rust can be treated with phosphoric acid. It will also convert any rust you may have missed from iron oxide into iron phosphate and stop the rusting. Applying Phosphoric acid to rusted areas ensures that your piece won’t jus start rusting again as soon as it is retreated. Ospho is a brand name of a liquid phosphoric acid product that works quite well. Make sure to protect your skin, eyes, and lungs from the acid. Read all warnings and wear gloves, eye protection and respirator when using acid. After the acid has had a chance to work, you can brush away any loose flakes.
- Wait about a day to make sure the acid has done all its work then prime the area using a metal primer coat. There are many brands out there to choose from as well as using a spray can or brush on.
- After the primer has dried use a finish coat of paint for metal. Spray cans or brush on are completely up to you.
If the item was oil or wax treated, get through step 3 and wait a day to let the acid work, and then you can gently heat the peice and apply fresh oil or wax, let sit for a few minutes and then wipe off the excess.