What it is
It is a salt formed where escaping acid vapour meets the metal of the terminal and clamp. A little of it around the positive post is common with age. A lot of it, quickly, usually means the battery is venting more than it should.
Why it matters
Corrosion is a poor conductor. Enough of it between post and clamp and the starter cannot draw what it needs, so the car cranks slowly or not at all — with a perfectly serviceable battery underneath. It also stops the battery charging properly, which then damages it for real.
When it means the battery is finished
Heavy corrosion that returns within weeks of being cleaned, a swollen case, or a smell of rotten egg near the battery all point to a battery that is overcharging or breaking down internally. Have it tested rather than just cleaned.
Find your battery
Which NOVAX® fits your car?
Read the code off the top or side of your current battery — three digits, sometimes with letters after them, like 628 or 646.
NOVAX® is fitted and warranted through Global Batteries Xpress and authorised resellers. Find your nearest outlet — they confirm the size against the car before anything is fitted.
Where to go
NOVAX® is tested, fitted and warranted at Global Batteries Xpress outlets and at resellers we have appointed in writing. The test is free whether you buy anything or not.