stainless as long as it is 316/18 or better...I need to mount a lamp post light that will have four exposed #10 x 1-1/2" wood screws. Are brass screws the only ones that will not rust?
The big box stores stock stainless in small quantities, often in blister packs Marine stores are another source. Brass is a poor choice, especially for wood screws. If you do not drill pilot holes or the wood is hard the heads can strip and the screws can break. Stainless steeel is the logical choice.Stainless steel are use extensively on boats , you are probably OK with only four of them because they are expensive by the box, ( but of course all hardware is getting expenive these days)they are not hard to find big box stores should have them along with hardware stores.