Why the spring had bad anti-corrosion ability?Because we change the raw material of the spring due to bad strenth from phosphor bronze to 65Mn, decrease the anti-corrosion ability, on the other hand, the coating thickness is too thin to meet the requirments.
Why both of the coating and raw material can't meet our requirments? Because there is no specification about the anti-corrosion ability demand on the drawing, otherwise vendor do not have the quality awareness to prevent the protential problem.