Pro-Spray 2K Etch Primer plus Activator 5L. Pro-Spray two pack etch primer offers the ideal initial protective coating when painting metal especially aluminium and alloys. This Pro-Spray Etch Primer provides an excellent surface for further painting. Many industrial specifications and schedules incorporate etch primers. Mixing Ratio 1:1. Supplied in a 5L tin with 5L of activator.