How to coat rust treat and recoat heat sensitive areas of an outdoor bbq?

[Brednet]

I have a hood type bbq grill that is on my deck in a harsh environment on the bay islands off brisbane that has had surface rust on the outside - this is both the outside cool and hot areas of the bbq. I had  sanded down the original paint and minor rust, cleaned with mineral turps and given two coats of White Night spray for metal that is subject to high temp from Bunnings and it looked great but after a few weeks the coating id disappearing and fine rust is returning. I visited my local bunnings and sought assistance from paint dept but they had no specific knowledge and could only scan the myriad of products on the shelf and read the directions as I has been doing. I assume I need to use some sort of metal primer good for combatting rust followed by a product that might be brushed on to give a thicker coat but it needs to withstand temps of 300-400 celsius I guess. Regular cooking temp is 180 though it has got to 250 before. Note this is not for the grill or anywhere near the food cooking areas which are fine

[JacobZ]

Hi @Brednet,

A warm welcome to the Bunnings Workshop community, and thank you for your question.

Unfortunately, you missed one crucial step in your first attempt, and that is to treat the rust with a rust converter such as this White Knight Rust Guard Rust Converter. Missing this step the first time has meant that the rust, while cleaned up with sanding, is still present beneath the layer of paint. Using a rust converter will convert the rust into a more stable, non-reactive compound that will not spread.

I would suggest removing the coating, applying the rust converter to any visible rust, waiting for the chemical reaction to occur, then repainting the surface with self-priming high-temp paint such as this White Knight Pot Belly Black Hi Temp Spray Paint.

This should give you a quality repair that will last for much longer than the initial one.

Let me know if you have any further questions.

Jacob

[Brednet]

Hi Jacob, 

thanks for the speedy reply, Is the Spray version going to be good enough for two coats or is even the white knight brands brush applied version likely to give a thicker more protective coat after the rust treatment undercoat for the very harsh rust environment I live in on Stradbroke Island. The BBQ i bought (Zieggler-Brown) became like this in three years. In fact the shop I bought it from didnt want to sell it to me but the alternative was a tiny aluminium BBQ. So I sort of want the repair job to be at least as resilient as the factory coat it came with. I dont mind re sanding and painting every couple of years until the structural parts rust but longevity is probably more important than looks ie I know they spray finish will look for even and aesthetic than a brush applied paint 

Bernie

[JacobZ]

Hi Bernie (@Brednet),

You can achieve a thicker protective coating using either the spray can or the brush-on White Knight Pot Belly Black High Temp Heat Resistant Paint. You would still aim to apply it in the same thickness per coat, just apply a few more coats. Three coats of either version should do the trick and ensure the metal is well encapsulated and rust resistant.

Some touch-up work every couple of years would also certainly go a long way, considering the rust-prone environment. With the likelihood of further work, it is likely more cost-effective to purchase the tin and apply it with a brush than it would be to use the spray can.

Let me know if you have any further questions.

Jacob