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Rustbuster 121 or POR-15 or something else?


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I went to the cupboard today and found that my two tins of Rustbuster 121 (quarter full each) were horrible and lumpy :cry:  So I need to buy some more. But do I? It's been a long while since I bought some and I thought there may well have been some developments in the rust prevention paint world.

Now, the Rustbuster 121 is fantastic stuff but it is a faff mixing it up, especially when you only need a little. It's also very expensive. Next, POR-15. I know this comes recommended and it doesn't need to be mixed - ready out of the tin, bonus :ani_clapping:  But, I've never used it. Is it as good as it is supposed to be? That leaves me with something else. What is there, if anything, that is on a par with the the others?

 

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What do you need to paint ?

 

I always use Rust Buster’s 121 & 421

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rustbuster first then either Epoxy mastic or POR 15 depending on whether it will be visible. If going POR 15 worth looking at the sets of small tins rather than one large tin - I did have a large tine seal itself shut despite my best efforts which was a bit of a waste!

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1 hour ago, PeterK said:

What do you need to paint ?

Hidden bits of car

 

1 hour ago, Roy M said:

rustbuster first then either Epoxy mastic or POR 15 depending on whether it will be visible. If going POR 15 worth looking at the sets of small tins.

The Rustbuster 121 is epoxy mastic. I like the idea of smaller tins as, as you say, less goes to waste. Is the POR-15 as good as the epoxy mastic though?

Edited by Phill
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Apologies - it was the FE123 convertor I was thinking of!

Hard to say which is best  - quite like the Por15 but really like the epoxy mastic. When I did my inner wheelarches I stripped back, metal cleansed, two coats of POR15 (grey then black so I could ensure two coats everywhere), then epoxy mastic followed by dinitrol. All still looks good more than 10 (probably nearer 20!) years later with only some dinitrol top ups in the meantime.

I know it sounds over the top but I only wanted to do it once so worth putting the effort in I thought.

Edited by Roy M
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I definitely prefer epoxy mastic. I found if the surface is too smooth POR15 can just peel off.  But you’re right, mixing it can be a pain.  I’ve used “tough paint” from euro car parts for quick squirts on various parts of our van and it seems to hold up OK but won’t be a match for the others. 

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I have some Jotun Jotamastic in dark blue thats pretty close to the colour of my car, perfect for touching up chassis stuff.  Available in various RAL colours, it's a 2 part epoxy so should perform the same or better than rust buster 121.

https://www.rawlinspaints.com/content/jotun-paints?gclid=CjwKCAjw2ZaGBhBoEiwA8pfP_jcmwGUMN-MWvcnqKeLaofp8rnQzrvqm0Fj-_2IKkSQS7DnZXkDRsxoC7GQQAvD_BwE

 

It's used on ships n oil rigs so got to be pretty good!

Edited by Nige
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12 hours ago, Nige said:

 POR15 isn't much better than hammerite.

I haven't found this - it does require good preparation ( I use their metal ready spray just before application) but it really sticks when you do that and lasts well. It's a pain to get off skin as well!

My experience with hammerite is a lot poorer although, in fairness, I probably wasn't as thorough when I last used it.

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18 hours ago, Nige said:

I have some Jotun Jotamastic in dark blue thats pretty close to the colour of my car, perfect for touching up chassis stuff.  Available in various RAL colours, it's a 2 part epoxy so should perform the same or better than rust buster 121.

I understand that 121 is rebadged Jotun Jotamastic Smart Pack and 421 is rebadged Jotun Penguard HB

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On 14/06/2021 at 15:47, PeterK said:

I understand that 121 is rebadged Jotun Jotamastic Smart Pack and 421 is rebadged Jotun Penguard HB

This is interesting. I did think 121 was the jotun stuff and asked them once if this was the case! I got a lecture about how their stuff is specially formulated and compatible with automotive top coats etc!!! I still went with the epoxy mastic though as I valued their extensive testing process.

Two points related to the original question

1) I think 2 pack paints will outperform the premixed formatulations, especially where good performance is required (clear coats etc). The premix stuff is handy, but my new method or mixing small amounts is to use a lolly stick to measure out a number of dips of paint into a glass dish.

2) Neither paint will stop rust that has set in and pitted the metal. Normally rust comes up from behind, so you have to get in from both sides to clean. The only way to stop the rust is an acid based dip, or cut it out completely.

Peter and I have discussed this a lot, but happy to get others view and experience to keep rust at bay.

Edited by osc911
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I am going to go with the Rustbuster again. I would go with the Jotun but the minimum size is 4.6l and a lot of that will end up going to waste through sitting on the shelf.

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16 hours ago, Phill said:

I am going to go with the Rustbuster again. I would go with the Jotun but the minimum size is 4.6l and a lot of that will end up going to waste through sitting on the shelf.

Want to go halves on the jotun? We are both in Surrey so easy logistics.

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I don't think it goes off/sets as it's two part mix.  The big tin I have is still fine after 3-4 years on the shelf.  There is usually something to touch up over the year and it always mixes fine.

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7 minutes ago, Nige said:

I don't think it goes off/sets as it's two part mix.  The big tin I have is still fine after 3-4 years on the shelf.  There is usually something to touch up over the year and it always mixes fine.

Me too. I've been using the same tins (black and grey) since about 2014. Both paint and hardener are as they were when new. I just mixed up a little a couple of weeks ago. Its great stuff!

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My rustbuster had had it. Shelf life on the website is12 months.

1 hour ago, osc911 said:

Want to go halves on the jotun? We are both in Surrey so easy logistics.

I think that would be far more aggravation than the saving would be worth but a good thought.

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I would say so, it's messy stuff to try and decant equally into separate tubs.

10 minutes ago, Phill said:

My rustbuster had had it. Shelf life on the website is12 months.

I think that would be far more aggravation than the saving would be worth but a good thought.

 

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22 hours ago, Phill said:

My rustbuster had had it. Shelf life on the website is12 months.

That's strange, I keep the tins upside down to play it safe with air getting in. I've had mine for 3-4 years. After a quick mix it's good as it was on day one. It shouldn't go off in air but maybe you got a bit of contaimination?

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