How to Clean Corroded Battery Terminals
By Pablo Zaldivar · Junior's Auto Repair, Twin Falls, ID
What You'll Need
⚠️ Before you start: Always disconnect the negative (black) terminal first and reconnect it last. This prevents accidental shorts. Wear gloves and avoid touching your eyes — battery corrosion contains sulfuric acid residue.
Turn off the engine and put on your gloves
Safety first. Make sure the car is completely off, keys out of the ignition. Gloves protect your hands from the corrosive material on the terminals.
Disconnect the negative terminal, then the positive
Use your wrench to loosen the clamp on the negative terminal (the one with the '-' or black color) and wiggle it free. Then do the same with the positive. Keep them from touching each other or the car frame.
Mix your cleaning solution and apply it
Mix one tablespoon of baking soda with one cup of water. Pour a small amount directly over the corroded terminals and clamps. You'll see it fizz — that's the baking soda neutralizing the acid. Let it sit for a minute or two.
Scrub with your brush
Use your old toothbrush or wire brush to scrub the terminals, the cable clamps, and any corroded areas on the battery posts. Work the fizzy mixture into all the nooks. Rinse with a little clean water and wipe dry with a rag.
Inspect the cables while you're in there
Take a look at the battery cables themselves. If the insulation is cracked, frayed, or the wire inside looks corroded beyond the clamp, the cable may need replacing. Worth noting before you put everything back together.
Reconnect the terminals and apply protector
Reconnect the positive terminal first, then the negative — the reverse of how you disconnected them. Tighten both snugly. Then apply a thin layer of petroleum jelly or a shot of terminal protector spray to help slow future corrosion.
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