Date tested: April 2018 | Price: £4 for 400ml | gt85.co.uk
GT85 is often cited by users as being superior to WD-40, but it’s very important to note that it is not sold as a corrosion protectant. Available in various sizes of can, this multi-purpose lubricant – owned by the WD-40 company – is easy to apply and relatively cheap.
Unsurprisingly, GT85 – which is not marketed as a rust inhibitor – performed very poorly in our corrosion test. After just one week the steel plate was more than half covered in rust, and completely corroded by the end of week five.
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 24 hours, the metal plate coated with GT85 had a matt finish, though was wet where the product had pooled. There was no discernible colour.
When dusted with sand, less was retained than on WD-40, and far less than the dedicated corrosion protectants. Once rinsed with water, all the sand was removed.
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.
Our O-ring soak test showed no damage whatsoever.
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.
In the case of corrosion protection, WD-40 is clearly better than GT85. This is consistent with how both products are marketed, but it’s perhaps worth noting that in a supplemental test of penetration, GT85 loosened a corroded bolt more effectively than WD-40 (control bolts were torqued to 15Nm, then corroded before being loosened with a digital torque wrench).
We will be testing multi-sprays at a later date, but for effective corrosion protection, we’d recommend one of the dedicated products below.
The full list of products tested is as follows:
To read the reviews of any of these items, please click here.