Platinum-coated titanium porous transport layers (PTLs) are commonly used in proton exchange membrane water electrolyzers (PEMWE) to ensure electrical contact and corrosion resistance on the anode side. While the impact of platinum on interfacial performance has been extensively studied, the effect of Pt coating thickness on dissolution stability is not well understood. In this study, model Pt/Ti thin films with precisely controlled Pt thicknesses ranging from 1 to 100 nm were fabricated using magnetron sputtering. The films were examinedusing operando scanning flow cell inductively coupled plasma mass spectrometry (SFC–ICP-MS). Our findings revealed that thin Pt coatings allowed Ti dissolution under the tested conditions, while coatings of 20 nm or thicker delayed Ti exposure during dynamic operation. In fluoride-containing electrolytes, only coatings of 100 nm effectively prevented Ti dissolution. These results highlight critical Pt thickness thresholds necessary to suppress Ti corrosion under the operating conditions typical in PEMWE and provide a mechanistic foundation for the rational design of PTL coatings before validating at the device level.