In this mini breakdown I walk you through the use of a normal scratches generator node I made. The node itself will be on Substance Share soon.
Graph. The green node is the normal scratches generator. The node takes any input, but grunges or scratches look best.
This is the input we are using, just a simple scratches generator.
When set to a value of 1 (the range is 0-1 for this node) the scratches are most intense. The node splatters the input around with several different angles in a normalmap.
When using a facing normal with the normal scratches as input, you get this mask which i use for masking roughness values. Doing it this way makes sure scratches are lined up in both the normal and roughness.
Without the normal scratches applied (value of 0)
With a value of 0.25, pretty subtle, but starting to show.
At a value of 0.50.
At a value of 1. A bit too much most of the time, but neat to have as an option.
Just a default grunge node, but used with the normal scratches generator node you can get a galvanised look with almost no effort.
With a grunge instead of scratches you get this galvanised look. Experimentation almost always pays off ;).
Test input - before.
Test input - after. Here you can see what the node does, just splattering the input around, with different angles.