If you’re modeling a railroad bone yard along with us, even if you’re just weathering models, one thing you’ll notice is that rust is everywhere. It is one of the most common enemies of steel railroad equipment. While the real railroads (and us modelers too) try to prevent actual rust from forming on our trains, recreating the look of this decay is an essential weathering technique.
What is Rust?
Rust is a natural process that occurs when iron, or metals containing iron like steel, come into contact with oxygen. The oxidation of the iron occurs at the atomic level, weakening the bonds between the iron atoms and consequently the strength of the metal overall. The presence of moisture hastens the process.
Rust appears as a reddish-brown. As it ages, it becomes darker in color. It can occur wherever ferrous metal is exposed to the air and moisture. Most commonly on rail cars, it will be found in greatest concentrations in places where water may collect and linger for a time. Places like the joints between steel sheets, rivets, posts, angles, etc. are often the source of the most extensive rust.
While rust weakens the steel, it takes a long time before this damage becomes extensive enough to pose a problem for the car. “Surface Rust” is just that – a thin layer of rust on the face of the metal that can usually be treated easily with sanding or a wire brush. It often looks must worse than it is as far as structural integrity is concerned.
Often much of the “rust” we see on railroad cars isn’t the oxidation itself but streaks of reddish-brown color washed down the painted sides of the car from the source of the rust itself. Of course over time this too begins to attack the carbody, but its damage is mostly cosmetic.
The more dangerous rust deposits are often the ones you can’t see. A leak in a car roof or window for example can allow moisture into the carbody. Trapped inside it will linger and trigger rusting at key structural junctions within the carbody. By the time you see its effects on the exterior, the rust has nearly consumed the internal structure of the car.
Of course stainless steel and aluminum rail cars will not rust – at least not those parts made of these materials. Other parts of the car, like trucks, frames, airbrake equipment, couplers, etc. will still rust.
To recreate the many varieties of rust appearance, you’ll need to use different techniques. That is part of the fun and beauty of weathering – no two cars are ever the same.
Heavy Rust with a Sponge
One of the most fun and effective ways of recreating the look of heavier rust is to use oil paints and a small sponge. The sponges used for applying make up are one of the most effective painting tools around. These can be found in the cosmetics section of most stores (I know, not familiar hunting ground for model railroad supplies!) and are cheap and disposable.
For color, either acrylic or oil paints can be used, but oils offer longer working time and, at least in my opinion, offer a better textured effect for this particular process than acrylics. They aren’t cheap, but a small tube will last a long time. Raw and Burnt Umbers and Sienas work well for recreating different shades and the paints can be mixed together for endless variation.
To apply the paint, simply put a little on the tip of the foam brush (scraps of similar foam from packing materials, etc. can also be used.) Dab the paint on in a stippling motion. This leaves not only the color and pattern, but also a fine and realistic texture to the rust.
Since rust spreads outward from the source and darkens as it ages, larger spots may show changes in color from brighter oranges and reds near the edges and darker browns in the center. To replicate this, build up you paint patch in layers, starting with lighter colors then adding smaller and darker coats.
You can also use the oil paint to create smaller rust details like the streaks which form down the sides of cars. You can use the edges of the makeup sponge or a small brush to drag the wet paint down the sides of the car.
A drybrushing technique works very well for this. Drybrushing is done by wiping nearly all of the paint off of the brush and then dragging the nearly dry brush down the car. This will deposit just a little color on the model and is easy to control.
You can also dip the brush in a little paint thinner or Turpenal then put the brush in the center of one of your rust spots and simply drag it down.
In all of these, the biggest trick is to keep the streaks vertical to mimic the effects of water and gravity.
Study pictures and practice and you’ll be surprised what you can do with just a few simple tools and supplies. Combine your oil paints with chalks and washes and you’ll be able to create some amazing models. Next week we’ll pull all of this together on a few models for the bone yard. The more you practice the better you’ll become, so what are you waiting for?