Rustproofing rhymes with:
proofing, proofing, roofing, goofing, proofing, roofing, spoofing, beefing, bluffing, briefing, chafing, choreographing, coffing, coughing, debriefing, doffing, dwarfing, engulfing, fireproofing, golfing, goofing, griffing, handcuffing, huffing, knifing, laughing, leafing, morphing, offing, photographing, proofing, puffing, rebuffing, riffing, rohlfing, roofing, roughing, ruffing, safing, sniffing, snuffing, spiffing, spoofing, staffing, strafing, stuffing, surfing, waterproofing