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Chemical etching of molds

I am facing with a problem regarding chemical etching with respect to p-20 material (1.2311) when this material was sent for etching (this is a bumper mold for a small car) after completion of the mold, during etching process it was noticed that the material was chipping off, what could be the reason as this has never happened during previous operation by using the same material.
Regards,

Ronald Raja
mold making - Mumbai, Maharashtra, India
2006

If the mold surface chipped off during etching, perhaps the previous machining operation was too aggressive and left tiny smeared but delaminated burrs, not visible until the acid exposed them. Less probable but it could also be something about the steel quality. Hard to say without seeing.

Guillermo Marrufo
Monterrey, NL, Mexico
2006

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April 12, 2010

Dear Mr. Ronald,
Following are the possibilities - in P20 material.
Since there is no normal practice of heat treatment before chemical etching, profiles and contours matter the most for the process you want to follow:
1. If you are planning too deeper (rough) surface finish on a slender areas.
2. If slender areas are finished by milling, grinding and there is no post normalising treatment done before chemical etching.
3. In real sense - Soon after machining, cracks due to material problem will not be known. You will notice this during polishing or chemical etching stage. Are you sure you did not notice this during polishing itself?
4. There is hardly any possibility where chemical can cause cracks. Worst possibility from chemicals could be abnormal pits.

Sanjeev
- Bangalore, India