Ah yes, been there: not only the welded ones. Some brands use a nice inox pulley but topside is fastened with a bolt that is not very seawater resistant. Somewhat hidden within the sail webbing (and within the top axle), it is worth a check for heavy corrosion. Ran thru a quiver once and had to replace 2/3, totally rotten, sliver holding it together. Ezzy pulley=one of the very best