FF: Forks Best Paint Finish for Girdraulics?

[Jim Bush]

It seems etch is a carry over from the old days when there were adhesion failures with automotive paint. It is still used in shops when time is short, ie in a paint production facilities, where time between coats is critical and the part needs to be out the door.

There is endless information on why etch is not really a good long term solution. It is an acid, deposits zinc to make the surface rough so paint will adhere, it is not rust treatment or prevents rust. It can't be used under body filla of any type, it remains "reversable" which means a year later you can still wipe it off with acetone or reducer. Epoxy is modern high-tech solution that is "not reversable" and has tenacious adhesion when used over a lightly sandblasted part.

I have 2pak paints that specifically warn not to be used over etch.

Make sure whatever paint you use is compatible with etch, if that is the route you go.

I must admit, it is hard to find an epoxy primer in BLACK, but any other colour primer will show through and ruin the whole look. I have found 2 products locally available, they are out there.

 

[Michael Vane-Hunt]

Having seen Jim's tank that he painted and lined, I get the feeling he knows of what he speaks.

 

[timetraveller]

Not necessarily applicable to our bikes but powder coat can be put on so that it does not rust. A local powder coating company near me got the contract to all the bollards along the sea front, probably several hundred to over a thousand items. The first coat is some sort of zinc loaded powder and then the final colour. They gave a twenty-year guarantee several years ago and the stuff still looks OK.

 

[Jim Bush]

Here is a pic of the RFM off Dan Smith's Rapide that he rode through South America and back. It was painted in 1974 in the typical red primer and black enamel paint. The stone chips and other damage has pretty much destroyed the paint and provided little rust protection.

I make the case for "THE" most robust and durable paint finish that can be afforded be used on these bikes.

Rattle can's and etch primers are not the best solution.

https://imgur.com/5ieMuku

 

[Tnecniv Edipar]

And this does work on aluminium? Asking because I recall hearing that the problem with aluminium is the surface oxide that develops almost instantly on newly cleaned material, so a special primer is required to chemically bond with the oxide layer.

 

[Jim Bush]

Yes,it does oxidize quickly. The manufacturer recommend application of primer within 4 hours of blasting.

Surface Preparation:
Option 1: Sanding
1. Once the Aluminum surface has properly dried from using Degreaser 10, mechanically sand the surface with 80-
120 grit for primers or primer surfacers or 180 grit-240 grit for low build primer sealers. A maroon nylon scuffing
pad can be used in hard to reach areas.
2. Once sanded, the primer or primer sealer must be applied within 4 hours to achieve optimal adhesion.
If the time between sanding and priming exceeds 4 Hours, the surface should be resanded.

Option 2: Sandblasting
1. Aluminum surfaces (Thick Wall) can be grit blasted as per Steel Structures Painting Counsel SSPC-SP6
Commercial Blast cleaning. Do not use steel shot or grit.
2. Remove any high profiles on the sandblasted aluminum by scuff sanding with 80 – 100 grit sandpaper prior to
application of the primer.
3. A minimum blast profile of 1.5 -2.5 mils is recommended for best primer adhesion
Aluminum oxidizes quickly, If the time between sandblasting and priming exceeds 4 Hours, the aluminum surface should be
brush blasted to refresh the surface.

Adhesion loss of paint finishes are generally the result of poor surface preparation.

 

[Tnecniv Edipar]

Ah ha! There you go then! So that's why there is so much trouble with painting aluminium! It can be imagined, all those restorers having their alloy parts blast cleaned and typically taking days to weeks, even longer before having them painted! Ideally then, it needs to be done on site at the painters premises, so the cleaning and painting is done without delay. Many thanks.

 

[Jim Bush]

There's also a big caution about using any cleaner/solvent/etch wash after blasting prep, it can lead to de-lamination issues.

Also, wearing nitrile gloves is critical in not transfering hand grease to the prepared parts.

 

[Jim Bush]

I am preparing to paint the girdraulic parts and RFM as we speak.

My process for painting is
- parts wash to remove as much grease, grime and dirt as possible. Scrape all built up layers of grit/grease in crevasses.
- go to U-Blast place, use their commercial equipment to remove the paint, down to bare metal
- at home, degrease, wash/rinse, air blow dry - use a compatible paint degreaser. For aluminum you can use an etch wash at this stage - not an etch primer - it has to be properly rinsed/dried.
- surface prep in my own blast cabinet with aluminum oxide media, handling with nitrile gloves. This is a light surface prep application only.
- quick sand to knock down high peaks, 80-120 grit paper
- air blow any remaining grit/dust
- mask areas, plug holes if necessary, still using gloves
- hang in paint booth - still using gloves
- apply two thin coats epoxy Black primer - allowing flash time
- after one hour, apply 2pak polyurethane black top coats, usually 2 good coats, not loading the surface, avoiding runs. If you need to sand out runs etc, you have to wait for the full cure / sanding period.
- leave to cure/dry. The paint I use says 5-6 days for full hardness cure. Touch dry is in a couple of hours, it needs to full cure before being put into use.
- any time you come back to re-coat, the part must be wet sanded with 400/600 grit after full cure

The short cut is to take your cleaned/de-greased parts to your powder coater who will blast and powder coat, done. Issues are they determine what gets masked/plugged and if they not familiar with the parts, it can be a real mixed bag. Powder coat is definitely the better option if you do not have access to a painter that will take time to do the proper process.

Advice with 2pak paints - I use an air supplied respirator in an exhaust-vented booth (temp controlled room) inside and get consistent results. You can paint outside if the temp is good and no wind, a face mask for paint would suffice. All painted parts would have to be brought inside to hang/cure and you run the risk of damage to the fresh paint any time you handle the parts.

 

[Tnecniv Edipar]

I would love to be able to do that myself but just don't have the space to accommodate the equipment and an area to paint without covering everything in the vicinity in over spray! For the amount of paint that I need to do it wouldn't be viable anyway. At least I know how to interrogate any potential paint shops now!
Would be great to see some images of the end result!