A long infight about the neccessity of priming went on – including the ususal research, talks to fellow builders and finally to my inspector – before arriving at the decision to prime but use the least hazardous method.

The main reason for the pro-priming decision was driven by the fact, that aluminum corrods easely and quicker than someone may naivly assume. ALCLAD is a very good protection – subject all parts remain unscratched which is difficult to achieve during the manifold construcution steps. For all non ALCLAD is a must as VANs advice and instruct.

Finally I decided to follow the product line of Stewart Systems https://stewartsystems.aero/ using EkoClean (1:30 diluted with distilled water), EkoEtch (1:2 diluted with distilled water) and as primer/filler EkoPrime. For spraying I used my SATA minijet 4400 (1.3mm nozzle) operated at 2 bar and dilluted the EkoPrime (after careful stirring) with 10% distilled water before filling (filtered) into the cup. Room (tent) temperature was abount 18°C while spraying. I tried to follow as close as possible (or doeable as non-spraying expert) the adice from Stewart Systems during preparation/cleaning/etching/scuffing and finally spraying. The results are far from perfect and definitely not suitable for covering the outside of the plane – nevertheless as always practice and experience is building up.

• Sufficient rinsing and rubbing with clear water after cleaning with EkoClean and etching/scuffing with EkoEtch is very important – in case of water stays and dries on the surface little stains are building up (darker than the scuffed aluminium surface). Obvious that is a residual which might impact the adhesion of the primer.
• I applied the primer less than 5 hours after preparation (Stewart Systems recommends not more than 10hours due to build-up of the oxidation layer)
• The smaller parts on the xxxxx were fixed with double sided tape on the back to the painting table
• Spraying at all is not complicated in case a tucky coat is sprayed first – followed by a wet coat after a couple of minutes – as EkoPrime dries fast this induction time is by far less than with epoxy based coatings
• Providing a little more space between parts on the spraying table allows to cover the flanges first before doing the wet coat on the horizontal surfaces
• Scuffing the Primer does require some effort – I had to do it on the top surfaces of the leading edge wedges to allow for covering the inside holes of the wedges