Topic: Honda CB fender rust - how to treat?

[kyle750]

Currently sorting an original K1 fender.  Top chrome looks very good with no dents or dings but the underside is rusted.  Kannika finished sanding off the rust but it is now exposed metal.  Were the undersides of original Honda CB fenders  galvanized?  What is the best treatment after refinishing and removing the rust.   I live in Thailand where it is very hot and humid so moisture trapped under a fender will rust very quickly.  Thanks!

[bryanj]

Silver Hammerit, or smoothrite, paint

[kyle750]

Silver Hammerit, or smoothrite, paint

Thanks mate.  Hammerite is available in Thailand.  Looks like a great paint for rusted metal.

[PeWe]

I sprayed my NOS fenders when I built my CB750 K2
(K1 rear fender, later K2- K6 front)

Rattle can
Sound-dampening sill protection that protects against stone chippings, corrosion, oil, petrol, water and salt.

https://www.biltema.se/en-se/car-care/car-maintenance/corrosion-inhibitors/sill-protection-spray-500-ml-black-2000047132

[BenelliSEI]

Silver Hammerit, or smoothrite, paint

Thanks mate.  Hammerite is available in Thailand.  Looks like a great paint for rusted metal.

My favorite solution too.

[lash]

Flexseal works well

[Don R]

 Truck bedliner is popular with the 4X4 guys, they use it underneath too.

[HondaMan]

Flexseal works well

+1 on this stuff. Nasty to apply, but sticks like it was made for the task.

[MauiK3]

After cleaning I have used Ospho to stop the rusting, self etching primer and then the top (under) coat of choice.

[Alan F.]

Evaporust followed by CorrosionX for me.

[kyle750]

Many thanks for all the helpful suggestions.  I will be limited to what I can buy in Thailand so still checking available options. Here is another photo of the sanded fender with a light coat of oil to prevent flash rusting.  I have the exact same dilemma with the tail light bracket.  Outer chrome is in excellent condition but the interior is heavily rusted.  I will be treating both at the same time.

[Kelly E]

I soak in EvapoRust, mask and spray the bottom with rattle can bed liner. Works great and helps protect the fender. As long as you are not going to show the bike in a big time bike show it's a good thing.

[dave500]

hammerite is great paint,we use it here in australia,be sure the surface is as rust free and clean as you can get it,sometimes overlapping metal makes it hard to scuff all sufaces,soaking in mollasses will get to the unseen areas,but youll need to paint straight away after rinsing it off.

[MauiK3]

You can also remove rust with electrolysis, simple and gentle, inexpensive. Re-coat with paint of choice right away, works great, won't harm the chrome like some other methods.

https://www.instructables.com/Electrolytic-Rust-Removal-aka-Magic/

[Stev-o]

... spray the bottom with rattle can bed liner.

+
1...I've used a similar product.  Doesnt look correct but really cant see it.

I think Hammerite is the route you should go.

[kyle750]

I think Hammerite is the route you should go.

Decided to go with the Hammerite. Fender was sanded and prepped very well.   Photo after the first coat of Hammerite Smooth Silver.   A very thick paint and needs to be well stirred. 2nd coat in 6 hours.  Looks to be a very good paint for rust treatment and prevention. Although the underside of the fender is not visible it is a good color match with a metallic sheen and looks like galvanized silver. 

Many thanks for the very helpful suggestions

[grcamna2]

I use a wood-handled wire brush to remove the rust and rough-up the underside surface of chrome fenders for paint to stick.
I used silver rattle-can paint,although after seeing the silver Hammerite,I prefer that. 

[kyle750]

A quick followup:  2 coats of Hammerite applied to the underside of the fender and interior of the light bracket - approximately 6 hours apart. Product spec sheet and instructions state that 1 coat is sufficient.    Hammerite is probably the thickest paint I have ever worked with.  In the can it actually looks like a liquid metal similar to a molten aluminum.  Very thick and gloopy and difficult to paint and spread.  I needed to work quickly as the paint became sticky and tacky very fast and overbrushing quickly became an issue.   Not a lot of working time with this paint.   

[grcamna2]

I like the look of that Hammerite;I was curious if it's available in the USA ?

[newday777]

I like the look of that Hammerite;I was curious if it's available in the USA ?

Apparently not. I searched yesterday but only saw UK suppliers.

[grcamna2]

I like the look of that Hammerite;I was curious if it's available in the USA ?

Apparently not. I searched yesterday but only saw UK suppliers.

  I'll keep looking,once the tariffs lift I might try to see if I can afford it.

[MauiK3]

I've never seen it either, especially not here in Hawaii.

[Kelly E]

I've mostly seen Hammerite paint in spray cans.

[bryanj]

Spray stuff just aint thick enough