Date tested: April 2018 | Price: £5.99 for 600ml can | www.wd40.com
WD-40 is sold as a multi-purpose spray, not a dedicated corrosion protectant. But it is marketed as offering protection against rust, and a lot of people do use it for that – it’s cheap and easy to apply from the aerosol can.
It’s available in various sizes, but this 600ml can ran out of propellant before the product was used up.
It’s important to note that this review is of standard, or original WD-40, not the new range of ‘Specialist’ products.
Consistent with similar, less controlled tests carried out in the past, WD-40 did reasonably well compared to some other non-specific products. After the first week there was little corrosion on the plate, but by week three it was almost half covered. From there the degradation was quite rapid, the metal being completely corroded by the end of week 11.
Fresh steel plates were cut to size, folded at 90° (to give vertical and horizontal surfaces), then thoroughly cleaned before being coated with each product, as per the manufacturer’s guidelines. The test was carried out indoors, with a reasonably regulated temperature. For more information on how the test was done, please watch the video below.
Morning and night, the plates were each sprayed with a 5% solution of road salt in water, then consistently rinsed off at the end of each week with a hose head set to a shower pattern.
After eight weeks, the hose head was switched to a more aggressive fan spray, and the plates were rinsed with a consistent five full strokes from a distance of one inch each time.
After 14 weeks, any products that hadn’t completely corroded were hosed off every evening.
After drying for 24 hours, the metal plate coated with WD-40 looked quite wet, but it didn’t retain much of the sand that was dusted on it for testing. Once rinsed, almost all the sand was gone, and it cleared entirely using a more aggressive fan spray.
Metal plates were cut to size then thoroughly cleaned, before each product was applied as per the manufacturer’s instructions.
The plates were left indoors, laid horizontally for 24 hours, then each was dusted with fine sand. The plates were tapped vertically to knock any excess sand off, before being assessed for stickiness.
Next, each plate was rinsed with a hose head set to a shower pattern, and the amount of sand left was assessed.
Finally, each plate was hosed with five full strokes from a distance of one inch using a more aggressive fan pattern, before being checked for any remaining sand. Both rinsing cycles represent the methods used during corrosion testing.
Soaking an O-ring in WD-40 for three months showed no swelling or damage, which is consistent with a previous soak test of more than one year. WD-40 is, however, a solvent-heavy product, and not suitable for lubing chains, or indeed control cables, the nylon linings inside which can be damaged.
Brand new O-rings kindly supplied by motorcycle parts specialist B&C Express were put into test tubes containing each product. These were left for three months to soak, before the O-rings were carefully removed and assessed for any swelling, cracking, or other changes to their structure.
Please note that we do not recommend using these products as chain lubes – we’re just using the O-rings as a consistent material.
Clearly standard WD-40 isn’t offering anything like the performance of dedicated corrosion protectants, but it is better than using nothing. Keep in mind though that some specialist cleaning companies suggest that prolonged use of such a powerful solvent on bare aluminium might cause tarnishing, and we would always recommend using one of the more purpose-made fluids tested below if you’re serious about stopping your bike from going rusty.
The full list of products tested is as follows:
To read the reviews of any of these items, please click here.