Depends too much on circumstances you have not told us.
Least friction is a smooth stainless steel loosely forced onto a smooth stainless steel.
Painted steel on painted steel (very tight, firm bond with little height or lumps on both pieces of steel) IF the steel is lightly loaded needs to be tested - This because the grip of paint-to-paint is unknown.
Once the paint gets thicker or more uneven, or if the load is great, or is intermittent and frequent, WILL cut through the paint layers quickly. This causes rust (much greater friction, probably two locked surfaces if carbon steel), or the scraped off paint will jam the previously sliding surfaces mechanically.