White or green powder on battery terminals is corrosion from acid vapour and moisture, and it causes poor contact and starting trouble. Clean the deposits off first, then protect the clean terminals with a thin film. Micron 4500 M.A.M.A Silicon Spray lists battery terminals among its electrical uses and is stated to prevent corrosion there; it is not stated to dissolve existing deposits. For cleaning contacts and removing carbon, Micron M.A.M.A (4102) lists cleaning and restoring electrical contacts.
Why it happens
- Acid vapour and moisture at the terminals. Batteries vent small amounts of acid vapour, which reacts with the metal of the terminals and clamps. Moisture and heat speed it up.
You will see white or green deposits on terminals and clamps, a loose or poor connection, and starting problems.
How to fix it
Two steps: clean, then protect.
- Cleaning contacts and removing carbon build-up: Micron M.A.M.A (4102). Its page lists cleaning and protecting electrical contacts and removing dirt and carbon build-up from arcing.
- Protecting clean terminals against further corrosion: Micron 4500 M.A.M.A Silicon Spray. Its page lists "Battery terminals (prevents corrosion)" and describes a moisture barrier that protects against corrosion and oxidation.
Directions for 4500, from its page:
- Shake the can well.
- Clean the surface of dirt, grease or moisture.
- Hold the can upright 15–20 cm away and spray a light, even coat.
- For electrical parts, make sure power is off before spraying.
- Wipe off excess with a soft cloth if needed.
General battery-care practice for the cleaning step: switch off the ignition and all loads, wear gloves and eye protection, remove heavy deposits mechanically with a terminal brush, wipe the area dry, make sure clamps are tight, then apply the protective film.
What to avoid
- 4500 is stated to prevent corrosion on terminals, not to dissolve existing deposits. Clean the deposits off first, then apply.
- Power off before spraying, as the 4500 page says.
- Treat both sprays as flammable until the SDS says otherwise. No sparks or flames near the battery, and use ventilation.
- Handle battery deposits with gloves and keep them off skin, eyes and paintwork.
- Do not let tools bridge the two terminals.
When to ask an expert
Go to a battery dealer or mechanic if:
- the battery is leaking, swollen or cracked; it needs replacing;
- corrosion keeps returning quickly, which can point to overcharging or a failing battery;
- the clamps or cables are corroded through.
FAQ
Which terminal should I disconnect first?
Follow the vehicle manufacturer's procedure. The common practice is negative first when disconnecting and negative last when reconnecting, so a spanner touching the body cannot short the positive terminal.
What is the white powder on my battery terminal?
It is corrosion caused by acid vapour and moisture reacting with the terminal metal. It increases resistance and can cause starting problems.
Can I just spray over the corrosion?
No. Clean the deposits off first. 4500 is stated to prevent corrosion on battery terminals, not to remove what is already there.
Does silicone spray affect the electrical connection?
The 4500 page describes it as non-conductive and lists battery terminals. Apply it after the clamp is fitted and tightened on clean metal, so the film protects the outside of the joint.
How do I stop terminals corroding again?
Keep them clean and tight, protect them with a thin film after cleaning, and have the battery and charging system checked if corrosion returns quickly.
See the product: Micron 4500 M.A.M.A Silicon Spray. Related: M.A.M.A 4102. More vehicle maintenance fixes: vehicle hub.