Light Aircraft Association

The 4130N steel hinge fittings for the wooden tailplane on my project have to be corrosion proofed. The plans call for them to be "tinned". The fittings will pass through holes which are to be sealed with polyurethane or epoxy. I had in mind having them plated/electroplated with either zinc, nickel or zinc/nickel and have seen various processes described on the web, but have just remembered that there is a note eslewhere in the plans advising against "plating" the metal parts, since this could lead to fatigue cracks if not done to aircraft standards. I seem to remember seeing warnings about plating elsewhere. Some of the web sites suggest that hydrogen “embrittlement” resulting from the plating process can be removed by a further process. This all sounds complicated and expensive.

I have found a small local firm who are happy to zinc or nickel plate my parts, but I doubt they have any expertise with critical components.

Any suggestions as to how I should “tin” these fittings? Alternatively, is there a modern/affordable plating process that might be a better choice and which would not risk causing adverse effects on the steel? The thickness of any coating should not exceed, say, 0.001", for obvious reasons. It would spoil my day if the elevators and/or the rudder fell off!

Zinc or Passivated Zinc plating is not as critical as chrome plating and doesn't have the same problems. We plated some parts on a restoration a while ago.

Don't forget that 4130 is more resistant to corrosion than most steels due to the addition of chrome and molybdenum. It is perfectly acceptable to simply paint it with an etch primer and then paint with a suitable 2 part paint - that is what nearly all metal parts on wooden aeroplanes end up with.

Thanks, Mike.

That sounds re-assuring.

Ian