As part of my environment I've made a Pipe trim sheet for the piping situated around the area. Non-tileable components are laid out with their own UVs, whereas the length of the pipe is tiling vertically with space horizontally for padding.
The base material is fairly simple and created in Painter. The real detail comes from the grunge decal applied to its own lower poly mesh over the pipe mesh.
In Painter I break the decal down into its R, G & B channels as masks. One channel acts as the opacity mask and is applied to a side of the mesh so as to feel like dirt gathering on the tops. General dirt is applied within the masked space so as to break up the appearance, and then a final leaking masks is applied beyond the original space to have more detail fit the contours of the shape.
Despite sharing the same texture each channel has its own controlling parameters for strength and tiling so as to make edits in the engine.
