Underside corrosion - preventative options

[Sundance]

I'm now 9 months into my 400h (07) ownership and have nothing bad to say about the experience.  Comfort, economy, service costs and overall enjoyment are all scoring high points.  I hope that I've landed myself a good'un 🤞.  So now that I'm looking at it being a potential long-term keeper the matter of preventative underside corrosion protection is on my to-do list as I know it can creep up on the older RXs.

At the moment on the ramp it's looking good, no sign of issues and I want to keep it that way so would welcome any suggestions and experiences as I've found a few seemingly quite different options regarding both cost and longevity. Hammerite, reportedly, lasts as an anti-corrosion solution for maybe 8-12 years ... but does it?  Then I've found the likes of Lanoguard, Lanox, Dinitrol and Waxoyl that appear to need more regular applications.

I'm really looking for sound recommendations, or even just considered pros & cons, so fire away good forum folk, I'm all ears.  What have you guys done?

[ColinBarber]

29 minutes ago, Sundance said:

 Hammerite, reportedly, lasts as an anti-corrosion solution for maybe 8-12 years ... but does it?

Only if it doesn't get chipped which obviously can happen on the underside of a vehicle. 8 years on some railings is different to the underside of a vehicle with stone chips flying about and road salt in the winter.

[Boomer54]

I have used Hammerite for all sorts of home uses and found it very durable beyond any other sort of paint. However, as Colin implies the finish is unlikely to survive the velocity of stone chips. There are plenty of alternatives that sidestep that issue.

[Jagman]

Years ago I used to use Waxoyl which can be messy and difficult, but now I can recommend Dynax UB which is a tough brown wax and comes in large aerosols so is very easy to apply and not at all messy. 
They also manufacture Dynax S50 to inject cavities in the same way. I’ve been using them for a long time on old Jaguars which are notorious for rusting!

[Jaystar77]

Can echo what Nick is saying there.

Have used different brands over a few cars now and always seem to come back to the Bilt Hamber stuff.  Used Dynax UC on Wednesday night in fact after installing some suspension.

No matter which you choose I would factor in an inspection every year or so just to touch up any signs of corrosion that might crop up.  

[Bluemarlin]

I also use the Dynax stuff, and here's what I've done to date.

Last year I sprayed any cavitities I could see with Dynax S50. I also removed the wheels and arch liners (one at a time), cleaned up inside the arches, covered the brakes with a plastic bag, and gave the area a good spray of S50, especially around the brake lines and fuel filler on near side rear. I then gave the underside a good spray of Dynax UB. Both Dynax products come in a can, with a fairly long 360 degree lance, as such they're easy to apply, particulary on an RX, which is high enough off the ground to reach most places. This took most of a day, and I then left it overnight for the Dynax to dry.

The next day, for good measure, I took a garden pump sprayer bottle and sprayed the underside with ACF 50.

I figure the Dynax is good for 2 or 3 years, so this year (this week in fact), I gave the underside a rinse with a lawn sprayer, and the following day gave the underside a good spraying of ACF 50, which only took about half an hour.

I will add that it's wise to put something under the car before you start, I used flattened out cardboard boxes from the recycle bins, to catch any drips, especially from the ACF 50, which is quite runny; and allow a day or so for things to dry off before using the car.

[Sundance]

10 hours ago, Bluemarlin said:

I also use the Dynax stuff, and here's what I've done to date.

Last year I sprayed any cavitities I could see with Dynax S50. I also removed the wheels and arch liners (one at a time), cleaned up inside the arches, covered the brakes with a plastic bag, and gave the area a good spray of S50, especially around the brake lines and fuel filler on near side rear. I then gave the underside a good spray of Dynax UB. Both Dynax products come in a can, with a fairly long 360 degree lance, as such they're easy to apply, particulary on an RX, which is high enough off the ground to reach most places. This took most of a day, and I then left it overnight for the Dynax to dry.

The next day, for good measure, I took a garden pump sprayer bottle and sprayed the underside with ACF 50.

I figure the Dynax is good for 2 or 3 years, so this year (this week in fact), I gave the underside a rinse with a lawn sprayer, and the following day gave the underside a good spraying of ACF 50, which only took about half an hour.

I will add that it's wise to put something under the car before you start, I used flattened out cardboard boxes from the recycle bins, to catch any drips, especially from the ACF 50, which is quite runny; and allow a day or so for things to dry off before using the car.

Good advice Bill, thanks 👌

[Bluemarlin]

17 hours ago, Sundance said:

Good advice Bill, thanks 👌

You're welcome Rowley. Another possible side benefit of the ACF 50, is that it's also a lubricant and, I don't know if it's the reason, but I don't have any suspension sqeaks or creaks.

Another quick tip is do it just after getting the car serviced and/or MOT'd, as the garage won't thank you for the oily mess if you do it just before.

[PCM]

I used Lanoguard...