Getting the rusted look on a muffler, or an exhaust pipe system is not easy. The paint guide on the instruction sheet will often ask modelers to paint the item a uniform red brown (sometimes called ‘Rust’), or worse still, just plain black. Neither colors are right unless they portray vehicles that had never been used are painted with a red primer.
Start with painting the object with an acrylic base using a very dark grey like NATO Black or German Panzer Grey. Then apply an overall fine dot scheme of enamel or lacquer based light grey. Here, I am using IJN Sky Gray. The dot pattern should coincide with areas of heavy corrosion/rusting effect.
Next, applying another dot pattern of an even lighter shade of grey, off-white or while enamel paint (here, I am using Model Master Camouflage Grey FS36622. These will be areas of even greater heat corrosion.
Apply a heavy thick oil wash of Burnt Sienna. Oil paint blob are OK as they simulate built up rust deposits. The oil solvent agent should be turpentine or turpenoid. The latter will partially dissolve the preceding enamel dots. That is the desired action, and should be left to do so. Leave to dry under a drying lamp if you have one. It will help the softening and dissolving action, but not too close in case you accidentally cook the part. Once dried, this will have a very strong and vivid orange hue. Do not worry!
Apply several layers of Sepia Shade from Vallejo wash range. This acrylic wash will tone down the strong Burnt Sienna oil wash nicely. Leave to dry.
Once the sepia shade is dry, apply chalk pastel colours of red brown, orange, and even some bright yellow to simulate uneven rust wearing. The exhaust pipe sections have been re-created.
