Am halfway through refurbishing a horsebox ramp…have stripped ply, wire brushed the rust off the box section frame and slapped some Hammerite Red Oxide on. Can only do three sides as the fibreglass wall is bonded to the fourth.

Was about to put new ply on but guy at work is telling me it needs a cellulose top coat as its porous or something?! It won't be exposed to weathering or sunlight, just needs to be able to cope with a bit of damp every now and then. Looks like it was originally treated with grey primer and it hasn't done too bad for six years old, just surface rust.

Instructions on back of tin just says it 'may be over painted after 24hours, most paints are suitable' Not must.

The resin binder isn't hazardous so it's not listed on the MSDS so I don't know what it is.

In my professional opinion I'd strongly suggest you over coat it. Anything marketed as a primer and not a primer finish or finish/topcoat is very unlikely to have the properties required to give a good lifetime. It is formulated purely for it anticorrosive and adhesion properties and isn't really tested to be for anything else. In industrial applications primers are formulated to last weeks not years as you expect a build coat and a finish to go on top.

You will not need to use a cellulosic specifically but just something that is suitable. If you are not that bothered about appearance then go for something cheap.

Thanks.

All I have in the cupboard is emulsion, gloss that takes 16hrs to dry and woodstain so its off down to Been & Queued for something cheap and quick drying 🙂

The cellulose paint will probably react with the red oxide (not compatible). Red oxide seems to work OK on the Forth Rail Bridge
http://www.leighspaints.co.uk/en/TA_Complex%20Cover%20Up.aspx

I don't think the Forth bridge is painted in standard red oxide 🙂 That article suggests the other extreme.

I just got some paint, £8, and have slapped it on. Eagerly waiting for it to dry (only 2 hours 🙂 )so I can get the ply down and paint on my £90/4 litre tin of granular rubber paint.