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Rust - Remove or Convert


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I am due to do hull blacking soon. Looking at Jenolite products they seem to do one that converts rust (I presume like kurust) and one that removes to bare metal. Any thoughts on which is better? I have always used the converter in the past, as it seems to be ok to just coat over it directly. Is this the case?

TIA

John

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The question will be how well does the blacking of your choice adhere to the converted rust. I suspect Jenolite rust converter (not rust remover) Kurust, and Vactan are all much of a muchness and leave a water based "primer" on the surface.

 

Normally for blacking the rust is removed by a twisted cup brush on an angle grinder and the the blacking is applied. However Hemple (was Blakes paints) said that a wire brush tends to polish the metal surface and make adhesion worse so I would give the wire brushed areas a quick go over with an angle grinder and course grit disk to provide a key of some kind.

 

I doubt a retail rust  remover will work fast enough for you. Fertan does not leave a primer on the surface and Keelblack advise its use  but it will probably add a day to the job. Apply as instructed and leave overnight, wash off the following day, wait to dry and then start blacking.

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Grind off any excess/loose rust, treat rusty areas with Fertan, wait 24hours for it to work then wash off residue.

The waiting and washing are VERY important.

Then apply blacking of choice.

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1 hour ago, Loddon said:

Grind off any excess/loose rust, treat rusty areas with Fertan, wait 24hours for it to work then wash off residue.

The waiting and washing are VERY important.

Then apply blacking of choice.

If you use Vactan you don't need to wash off.

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OK

Perhaps some refinement.

In the past I have used Kurust , after the hull has been pressure washed and hand wire brushed where rust shows. Since this is water based I have seen no issue in doing the same day as the washing.

I prefer not to grind,  since this seems to be a waste of the steel I paid for. :-)

I am lead to believe that the residue is ready to be over coated.  Perhaps a brief go with hand wire brush would aid keying? Would this cover the "How well does it stick" aspect as Tony mentioned?

I am only using bitumastic by the way. Not sure how well that sticks anyway?

 

John

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2 hours ago, Floating Male said:

OK

Perhaps some refinement.

In the past I have used Kurust , after the hull has been pressure washed and hand wire brushed where rust shows. Since this is water based I have seen no issue in doing the same day as the washing.

I prefer not to grind,  since this seems to be a waste of the steel I paid for. ?

I am lead to believe that the residue is ready to be over coated.  Perhaps a brief go with hand wire brush would aid keying? Would this cover the "How well does it stick" aspect as Tony mentioned?

I am only using bitumastic by the way. Not sure how well that sticks anyway?

 

John

I like Vactan. I've used it to treat chips and bubbling rust patches on the roof and weather deck to get them through the winter without over coating it and the results have  been good. Chips seem to be fettled long term and even treated patches on flat places like the roof and gutter area  that can suffer puddling stay rust free for a long period without gloss on top before they need re addressing.  Areas where I've primed and glossed on top of Vactan, like scrapes on the tunnel band, and on the gunwales where I've topcoated with Andy Russell's Gunwale Black, have had no issues.  I did my gas locker floor a year ago, treating the rusty patches with Vactan and coating over it with a single coat of Rylards Premium blacking.  It dried to a smooth, fine finish and still looks perfect. Similarly, I've treated scrapes on the sides below the top guard irons which had rusted and have then applied coats of Premium and Rytex over it without problems.

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17 hours ago, Richard10002 said:

I’ve used Vactan in my engine space and, having left it for a few weeks before overcoating, the rust had begun again, so I gave it another coat, just to be on the safe side.

 

Which, if the manufacturer is to be believed, wouldn't happen if you used Fertan. However, Fertan is supposed to be rinsed off after 24 hours; I haven't sufficient knowledge of the chemistry to understand why.

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1 hour ago, George and Dragon said:

Which, if the manufacturer is to be believed, wouldn't happen if you used Fertan. However, Fertan is supposed to be rinsed off after 24 hours; I haven't sufficient knowledge of the chemistry to understand why.

From observations. Some of the Fertan seems never to react so you are left with black dust (I think reacted Fertan), adhering black coating (reacted Fertan) and a sort of soft brownish almost varnish (I think dried unreacted Fertan). The washing off removes the dust and unreacted Fertaan but on horizontal surfaces getting it clean is easier said than done.

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7 hours ago, Tony Brooks said:

From observations. Some of the Fertan seems never to react so you are left with black dust (I think reacted Fertan), adhering black coating (reacted Fertan) and a sort of soft brownish almost varnish (I think dried unreacted Fertan). The washing off removes the dust and unreacted Fertaan but on horizontal surfaces getting it clean is easier said than done.

Plus you’re adding the one thing you don’t want if you’re de-rusting: moisture. 

  • Greenie 1
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13 minutes ago, WotEver said:

Plus you’re adding the one thing you don’t want if you’re de-rusting: moisture. 

I don't think its an issue as long as the reaction has formed it surface. Certainly it has not seemed to be on the cabin sides under the window frames I did several years ago. Now, the well deck was another matter probably down to the unreacted Fertan and the back dust. The paint lifted off almost in sheets. That is why I am trying Vactanesque products.

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25 minutes ago, WotEver said:

Plus you’re adding the one thing you don’t want if you’re de-rusting: moisture. 

Not a problem if using water based blacking as I have done, A year to go before i report back on Keelblack looks fine so far.

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On 19/07/2018 at 11:41, Tony Brooks said:

The question will be how well does the blacking of your choice adhere to the converted rust. I suspect Jenolite rust converter (not rust remover) Kurust, and Vactan are all much of a muchness and leave a water based "primer" on the surface.

 

Normally for blacking the rust is removed by a twisted cup brush on an angle grinder and the the blacking is applied. However Hemple (was Blakes paints) said that a wire brush tends to polish the metal surface and make adhesion worse so I would give the wire brushed areas a quick go over with an angle grinder and course grit disk to provide a key of some kind.

 

I doubt a retail rust  remover will work fast enough for you. Fertan does not leave a primer on the surface and Keelblack advise its use  but it will probably add a day to the job. Apply as instructed and leave overnight, wash off the following day, wait to dry and then start blacking.

I've never had a problem with any primer, bitumen or epoxy not sticking to any areas that I've taken back to bare steel with a wire wheel on an angle grinder. That includes the bilges of two c1890s 90ft passenger boats that we epoxied. That job was overseen at one point by the paint manager of the Cutty Sark project. 

 

Also a course grit abrasive will take off good steel - not a good idea. 

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8 hours ago, blackrose said:

I've never had a problem with any primer, bitumen or epoxy not sticking to any areas that I've taken back to bare steel with a wire wheel on an angle grinder. That includes the bilges of two c1890s 90ft passenger boats that we epoxied. That job was overseen at one point by the paint manager of the Cutty Sark project. 

 

Also a course grit abrasive will take off good steel - not a good idea. 

I only reported what Hemple wrote but if a course disk will take no more good steel off with a "quick go over to give some kind of key" that would be taken off if you were trying to mechanically remove the rust from rust pits in the steel. in fact there would be less removed because you are not tying to remove pits, you are just scratching the surface.

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2 hours ago, Tony Brooks said:

I only reported what Hemple wrote but if a course disk will take no more good steel off with a "quick go over to give some kind of key" that would be taken off if you were trying to mechanically remove the rust from rust pits in the steel. in fact there would be less removed because you are not tying to remove pits, you are just scratching the surface.

I once worked on maintenance at a place where they repaired road tankers. When the shells got pitted, they removed rust from the pitting with an air driven needle gun. Extremely effective though extremely noisy. Blasting was of course another alternative if larger areas were needing attention.

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38 minutes ago, catweasel said:

I once worked on maintenance at a place where they repaired road tankers. When the shells got pitted, they removed rust from the pitting with an air driven needle gun. Extremely effective though extremely noisy. Blasting was of course another alternative if larger areas were needing attention.

Agreed, but those options are not available for most [people doing DIY blacking.

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Purely for information.  I read recently where bicarbonate of Soda is used as the medium for shot blasting.  Apparently it is a less aggressive product and leaves a better finish on the steel.  Obviously not a DIY job but there are mobile operators.  

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4 hours ago, Dartagnan said:

Purely for information.  I read recently where bicarbonate of Soda is used as the medium for shot blasting.  Apparently it is a less aggressive product and leaves a better finish on the steel.  Obviously not a DIY job but there are mobile operators.  

I have seen this process used to blast cars prior to restoration on TV. They certainly seem to do the job. Some good clips on youtube too.

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