Rusty trailer- which zinc spray to use?

[Sea Change]

Not exactly a boaty question, but I'm fixing up a little garden trailer just now and noticed some superficial rust on the (galvanised) mudguards etc.
I've not had great results with zinc spray before but maybe I wasn't buying the right stuff.
Any recommendations for which ones are any good? I gather it's all about the zinc content but in finding it surprisingly hard to get numbers for most of the cans I've seen on sale.

 

[Boater Sam]

Just spraying rust with zinc paint is a waste of time and money,
.
You need to remove the rust and treat with a rust converter first.

 

[Sea Change]

Just spraying rust with zinc paint is a waste of time and money,
.
You need to remove the rust and treat with a rust converter first.

Sorry I didn't mean that I would just spray over existing rust, obviously I'll wire brush it back first.
Trying trying to find out which spray has the most zinc, and which ones are just silver paint!

 

[wonkywinch]

I've used the Hammerite product on cast iron manhole covers and it works well.


Hammerite Direct To Rust Metal Paint Aerosol Smooth Finish - Metallic Paint | Hammerite

 

[penberth3]

Sorry I didn't mean that I would just spray over existing rust, obviously I'll wire brush it back first...

Wire brushing is also a waste of time, it leaves you with polished rust. You need something more abrasive.

 

[VicS]

Sorry I didn't mean that I would just spray over existing rust, obviously I'll wire brush it back first.
Trying trying to find out which spray has the most zinc, and which ones are just silver paint!

Wire brushing alone is unlikely to be satisfactory. I have had good results with Fertan rust converter.

Regarding zinc rich paint .I remember my father having good results with Galvafroid many decades ago. The dry film contains 90% zinc by weight.

.

 

[Sea Change]

Wire brushing is also a waste of time, it leaves you with polished rust. You need something more abrasive.

I'm a bit worried that anything more aggressive might not leave much of the thin metal behind!
I'm mostly doing this for cosmetic purposes so that the plod don't feel the need to take too close a look at me...

 

[Plum]

Not exactly a boaty question, but I'm fixing up a little garden trailer just now and noticed some superficial rust on the (galvanised) mudguards etc.
I've not had great results with zinc spray before but maybe I wasn't buying the right stuff.
Any recommendations for which ones are any good? I gather it's all about the zinc content but in finding it surprisingly hard to get numbers for most of the cans I've seen on sale.

Yes, it's all about zinc content, and you are going to get much more of it in the dry paint film if you use a cold galvanising paint applied by brush rather than spray can.

 

[rogerthebodger]

The best way is to grit blast the trailer frame then have the frame hot dipped galvanized for a long-lasting result.

I have a boat trailor thwt I plan to treat it the same way

 

[Sea Change]

The best way is to grit blast the trailer frame then have the frame hot dipped galvanized for a long-lasting result.

I have a boat trailor thwt I plan to treat it the same way

I'm sure you're right, but this is just a quick fix so that I can do a couple of jobs with this trailer.
The actual drawbar and axle are in pretty good condition, the suspension units have a lot of flaking surface rust but seem solid, and the body panels have isolated rust patches that I want to treat before they get any worse and rust right through.

 

[thinwater]

Grit blasting may leave holes!

The rust conversion process is simple. Brush on a phosphoric acid solution (there are commercial conversion products also--not much different), wait an hour, hose off. The rusted areas will have turned black. Give a light scrub to remove excess, then paint.

Makes a big difference.

 

[Sticky Fingers]

I use Jenolite for this. Other products also available from reputable suppliers eg Dinitrol. The key this as said by others is to use a product that converts the rust into a stable surface that can then be primed and painted. This conversion of the surface from a rusty corroded mess to something that you can reasonably expect to be painted is critically important to ensuring a long lasting fix.

As far as finishes is concerned, I favour the Hammerite products as mentioned above. Use a zinc phosphate primer first, then a couple of coats of your preferred finish. Some finishes require lacquer over the top. Another point to mention is do not attempt to do this when the temperature is lower than the figure recommended by the paint manufacturer, this will inevitably result in a lower quality outcome.

 

[penberth3]

...As far as finishes is concerned, I favour the Hammerite products as mentioned above. Use a zinc chromate primer first,...

I'm not sure if Chromates are still available or even legal? Whatever, I wouldn't use anything as nasty. Plenty of safer options.

 

[2Tizwoz]

Not exactly a boaty question, but I'm fixing up a little garden trailer just now and noticed some superficial rust on the (galvanised) mudguards etc.
I've not had great results with zinc spray before but maybe I wasn't buying the right stuff.
Any recommendations for which ones are any good? I gather it's all about the zinc content but in finding it surprisingly hard to get numbers for most of the cans I've seen on sale.

Haven't had success with spray cans but Smith and Allen zinc rich paint is long lasting. Very high zinc content and lasts for many years in my experience. Also whilst wire brusbing isn't recommended I find the zinc rich adheres without a problem. I've succesfully used a wire brush on an angle grinder. You could hand sand after the wire brushing to leave a somewhat rougher surface.

 

[Sticky Fingers]

Phosphate. Not Chromate.

 

[MM5AHO]

A simple way to test the zinc content of zinc rich paints is to compare the weight with a similar volume can (aerosol or liquid only paint, applies to both). Many cans of this type of paint contain aluminium to match the colour of fresh galvanizing. The aluminium does little in this case for protection (not zero, but not as good as zinc).
Pick up the can, if it doesn't feel heavy enough to think "that feels heavy", then reject it. Zinc is about 7 times the density of water, it feels heavy.
Someone mentioned galvafroid. If you can get it, its very good. There are others. Relying on the printed "XX% zinc in the dry film" on the can can be quite misleading, as this is often "optimistic".

 

[DownWest]

A simple way to test the zinc content of zinc rich paints is to compare the weight with a similar volume can (aerosol or liquid only paint, applies to both). Many cans of this type of paint contain aluminium to match the colour of fresh galvanizing. The aluminium does little in this case for protection (not zero, but not as good as zinc).
Pick up the can, if it doesn't feel heavy enough to think "that feels heavy", then reject it. Zinc is about 7 times the density of water, it feels heavy.
Someone mentioned galvafroid. If you can get it, its very good. There are others. Relying on the printed "XX% zinc in the dry film" on the can can be quite misleading, as this is often "optimistic".

First point on any of this is to ensure the rust has not compromised the structure, as all these 'treatments' are preventative or cosmetic.

Case: Local friend asked if I could tidy up his light trailer. I collected it from a mutual friend, only to have the cross section/axle seperate from the main part on the way to here. The rust didn't look too bad, but had gone right through the main joint.

Actually using a product by Owatrol, Rustol. One puts it directly on the brushed rust and it seals and stabilizes the rust. Brushing is by a serious knoted effort on a heavy grinder, followed by chipping.
Not a trailer, but some ancient wrought iron railings and gates. Rust on them is quite different from steel and has to be chipped off, after the 'loose' stuff has gone.
No confidence in any spray can, just paint.

 

[Neeves]

Any thread can include anchors

Its common place for anchors to be sprayed with an aluminium spray paint to cover defects in the galvanising. Aluminium is used as a rust inhibitor.

Jonathan

 

[ghostlymoron2]

A simple way to test the zinc content of zinc rich paints is to compare the weight with a similar volume can (aerosol or liquid only paint, applies to both). Many cans of this type of paint contain aluminium to match the colour of fresh galvanizing. The aluminium does little in this case for protection (not zero, but not as good as zinc).
Pick up the can, if it doesn't feel heavy enough to think "that feels heavy", then reject it. Zinc is about 7 times the density of water, it feels heavy.
Someone mentioned galvafroid. If you can get it, its very good. There are others. Relying on the printed "XX% zinc in the dry film" on the can can be quite misleading, as this is often "optimistic".

I disagree with your opinion with Galvafroid, electricians tend to use it to protect cut edges on cable tray. After a few months you can peel it off in strips.

 

[penberth3]

I disagree with your opinion with Galvafroid, electricians tend to use it to protect cut edges on cable tray. After a few months you can peel it off in strips.

I've never seen electricians bother with anything like that! I'll guess they just slap it on with no preparation. Don't blame the paint.