Currently we start a chemical etching project. This project involved etching a polished titanium grade 5 surface part.
We facing a problem where by our etch resist coating peel off during etching process.
As per suggest to us by the coating supplier, the titanium parts surface were pre-treated, with anodic cleaning (20wt% NaOH, 10V/14A , 5 minutes) and H2SO4 acid dipping (60 wt% at 5 minutes), rinse and coating.
For coating, we used electrophoretic deposition (EPD) process, and use cataphoretic lacquer as its coating. After cure at 160C for 30 minutes, we strip of some coating layer to make a character/artwork by using LASER engraving.
For etching, we used HF/HNO3 (13/22 wt%) around 5 minutes and 21deg C. the target depth for the etching is 100um. the parts dimension is around 5mm (L) x 3mm (H) x 4mm (W).
We understand the coating provide is very good in term of aesthetic, but it somehow wont withstand etching and peel off.
Is there any suggestion on the similar or other method of coating for the etch resist on titanium polished surface?
For Ti alloy etching for better adhesion , i sugges to you using H2O2 with HNO3 and HF ,this mixture is highly effective to ttt titanium or Ti alloy surface before any coating ttt.
You can use my paper for nanotitania tube preparation as a guide for ur preparation.
Dear Faizall Mohd,
did you check if your coating material is able to withstand HF and HNO3? Does the coating start peeling of from the sport where you did the laser engraving?
Best regards,
Dear Mark,
Thank you for your response.
Before laser engraving, where all surface was coated with etch resist, coating has no problem to withstand HF/HNO3 at mentioned concentration.
And you are right, the spot where the peel off is start from the engraving area. Noted that we do have study to reduce the laser depth and we control ot to only engraved the coating surface, but the peel off still occured.
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