I make my own al pins by buying rod from the hardware store. They cost just a few bucks and can be changed as soon as they show appreciable wear. Easy and cheap enough to carry an extra pin if afraid one might break. Anyone tried delrin
for pin material? Stuff is tough as nails and has great wear characteristics.
There are literally hundreds of aluminum alloys and heat treatments. Some alloys are specifically for corrosion resistance; heat treating can more than double the strength. I have no idea what's on the shelf at the hardware store. I'm willing to spend more than a couple of bucks to keep several hundred dollars of rudder, castings and tiller arm attached to the boat.
The most common marine aluminum is 6061-T6. It's what all the extrusions are made from on a Hobie. T6 tempering means that it's solution heat treated and artificially aged (in an oven).
I'm not sure what is used for the castings, since 6061 is meant to be wrought (extruded). Probably a 3XX.X series alloy, since it is metallurgically similar to 6061 (alloyed with Mg and Si).
The point being, that you want a pin that's somewhat metallugically similar with the castings and/or the gudgeons or you'll have a battery when it's all put in salt water. Inferior Al alloys (lower on the galvanic scale) will end up being sacrificial anodes. I'd rather not have my rudder pins be "sacrificial" for the reason stated above.
Stainless pins are great (I use them), but if you need to use plastic bushings in the castings, or else they will fuse to the castings from galvanic corrosion.
You can get 3/8" 6061-T6 rod in various specifications (including certified material, hard coat anodized and chrome coating) for $2/ft - $8/ft (chrome) from McMaster-Carr. 3/8" 316 stainless steel rod is $3.50/ft. You can also get 3/8" titanium rod for $38/ft
Delrin (acetal copolymer) is unsuitable for rudder pins. It has about 1/3 the tensile strength of aluminum and very low impact resistance. Makes great bushings and rudder shims, though.