Tensile strength is the pulling of a material until it tears apart.
The higher the tensile strength, the more susceptible it is to embrittlement.
When you chrome a part, hydrogen is soaked into the material as it
is plated, the plating then holds it in. Once inside it will spread
to all areas, where it is relatively harmless. When stress is
applied, the hydrogen re-distributes itself, concentrating on the
point of stress. Think of it as trying to escape, and its only way
out, is a crack. Metallurgists do not know how a crack is formed.
That is still in debate. The moving and concentration however,
is not. "Presently this phenomenon is not completely understood
and hydrogen embrittlement detection, in particular, seems to be one
of the most difficult aspects of the problem. Hydrogen embrittlement
does not affect all metallic materials equally. The most vulnerable
are high-strength steels, titanium alloys and aluminum alloys."
When enough hydrogen accumulates, and a crack is
established, it focuses on the end points of the crack. Until it
becomes so weak that the end of the crack moves, the hydrogen then
follows to the new highest stress point. The new end of the crack. Until
the whole thing fails suddenly.