Underseal?

[sproutdreamer]

My 04 Yaris is very rusty underside and I am in the process of removing all the surface rust (happily no holes yet) , then to coat with Hammerite and then underseal and hopefully get a few more years as it is mechanicaly very good and only 45K. There seem to be very limited options for under seal Totroseal or Hammerite Underbody Seal with added Waxoyl. I am thinking the Hammeite seal as I could brush on the easy areas and suspension arms and then use a spray of the same stuff for bits hard to access. My question is how does the Hammerite underbody seal dry - does it set to a hard but flexible coationg or just stay soft and perhaps sticky?

[monkeydave]

hammerite underbody seal is really good, once set it is like candle wax (not as hard) and doesnt run off  ive had lots of luck with it over the years

it does dry pretty hard and is not sticky when fully dry and wont come off when you touch it after a day or so

 

you cant paint over it so it will be the final coat you apply and leaves a black finish

[Madasafish]

Personally I would treat the surface after derusting - there will always be some rust left.. Any of the acid based derusters will neutralise the rust left and provide a good base for painting.

 

Waxoyl based underseal is like soft cheese- it does not survive being hosed by a mix of water and stones very well.

 

I use Dinitrol 4941 https://www.dinitroldirect.com/car-underseal/  available on eBay. Our Yaris is virtually rust free as a result - and it resists water/stones better. And you spray it on.

 

I also treated a VW Sharan for a friend.. directly on to top of untreated rust - just wire brushed the flakey bits. OK after 2 years ,,

 

A pit or HIGH axle stands make life easier plus eye and nose protection.. Dinitrol 4941 stinks when applied - I apply in a pit and 20 minutes work and then a rest to allow smell to clear - it vanishes when dry.