Can iron remover be used safely on alloy wheels?

Usually yes, when the product is explicitly rated for the wheel finish. Painted and clear-coated alloy wheels generally tolerate automotive iron removers well, but bare, polished, anodized, chrome or damaged finishes may require extra caution and shorter dwell times. Apply only to cool wheels and rinse thoroughly, including behind the spokes. If a wheel has chipped or peeling clear coat, keep dwell times short, because chemicals can reach the bare metal underneath and cause staining or corrosion.