In this tutorial, I will show you how to make a procedural grunge material using the shader nodes in Blender for your project.
Grunge Base
Make sure you have the Node Wrangler add-on activated
In the Shading Workspace, add a Musgrave Texture node
Select the Musgrave Texture node and use CTRL + T to add a Texture Coordinate and Mapping node
Change the output of the Texture Coordinate to Object
Connect the Musgrave Texture to the Base Color of the Principled Shader
Make adjustments to the Musgrave Texture node to change the size and look of the texture
Add a Wave Texture node and change the Type to Rings
Select the Wave Texture node and use CTRL + SHIFT + LMB to view the node
Make any changes to the options as needed to make wavy stripes
Add a Separate XYZ node and connect the Texture Coordinate node to the Separate XYZ node
Add a Combine XYZ node and connect the X and Z outputs of the Separate XYZ to their corresponding inputs of the Combine XYZ node
Connect the Height of the Musgrave Texture node to the Y input of the Combine XYZ node
Connect the Combine XYZ node to the Vector of the Wave Texture
Connect the Wave Texture to the Base Color of the Principled Shader
Reconnect the Principled Shader to the Material Output
Group
Select these six nodes and use CTRL + G to group them
Open the Properties Panel using the N-key
Grunge Color
For some color, add a Color Ramp between the Wave Texture and the Group Output
Change the Black Color Stop to a dark brown [#4C2C18]
Add a third Color Stop and change the color to a dark green [#404921]
Change the White Color Stop to a darker brown [#532211]
Connect the Factor of the Wave Texture to the second input of the Group Output node
Under the Group tab, add two Inputs – one for Scale and the other for Amount
Add two Math nodes
Connect the Scale from the Group Input to the top Value of each of the Math nodes
Connect the first Math node to the Scale input of the Musgrave Texture
Set the Value of the first Math node to 2 and change the Function to Multiply
Change the Function of the second Math node to Multiply
Connect the second Math node to the Scale of the Wave Texture
Connect the Scale output of the Group Input node to the Detail input of the Wave Texture
Add a Mix Color node between the Color Ramp and the Group Output
Change the connection of the Color Ramp to the bottom input
Change the Color of the top input to white
Add a second Mix Color node between the Factor of the Wave Texture and the Factor of the Group Output
Change the connection of the Color Ramp to the bottom input
Change the Color of the top input to white
Connect the Amount output of the Group Input node to the Factor of each of the Mix Color nodes
Press TAB to exit the group and rename the Node Group
Texture
Add a Diffuse Shader and a Glossy Shader
Use a Mix Shader to combine these two Shaders
Duplicate the Mix Shader and place it between the Principled Shader and the Material Output node
Connect the first Mix Shader to the bottom Shader input of the second Mix Shader
Connect the Factor of the Grunge Node Group to the Factor of the second Mix Shader
Connect the Factor of the Grunge Node Group to the Roughness of the Glossy Shader
Displacement
Change to the Cycles Render Engine
Add a Math node and change the Factor to Multiply
Connect the Color of the Grunge Node Group to the Value of the Math node
Connect the Value of the Math node to the Displacement of the Material Output Change the Scale and Amount of the Grunge Node Group