It's been my experience that any brittle coating will show cracks when the substrate deforms. I use it to discover where deformation has occurred. Chrome either cracks or flakes. Powder coat cracks unless it is very elastic. Paint cracks. Even mill scale, the blackish stuff on the surface of hot rolled steel, will crack if the part deforms.

Of course, I was using something I had already learned. An older way of determining strains in parts (before finite element analysis) was to make a part and coat it with special paint called "brittle coat". Then load the part. Remove the load and inspect the part. Cracks in the brittle coat would be perpendicular to the strain. One could tell from the cracks what strains were occurring.

R.