Cobalt rhymes with:
thunderbolt, asphalt, creditanstalt, ehrenhalt, galipault, greenawalt, hanawalt, kreditanstalt, pennwalt, pinsoneault, rachelvolt, somersault, thunderbolt
Cobalt sounds like:
cabled, capability, capaldi, capaldo, cappelletti, casebolt, caufield, chavalit, civiletti, civility, cobbled, cockfield, coffelt, coffield, cofield, copilot, copulate, coupled, covalt, covault