Surface rust in bilge - treatment

[Guest]

Hey all,

 

Had an engineer do a bit of an engine service/tutorial on how to service my engine a short while ago. He suggested I spent a bit of time in the bilge and treat the surface rust. It's really not bad at all - as in not lumpy rust, just like a fine coating of rust. I did climb down into the bilge and while I've got a reasonable amount of room down there, it's still a little tricky to access all of it. So essentially getting in with an angle grinder for the majority of it could be tricky. As I say, the rust is pretty light and so am wondering if I could almost just apply fertan to it, let it do its job and then pour a load of red oxide primer over it?

 

How effective is fertan on light rust? Or would vactan or something else be an option? I could with a bit of effort and a small wire brush probably get into some of the cracks and crevices and I have every intention of doing what I can but as of yesterday turning 45, I feel like I'm not quite as supple as I was on Tuesday! I'll update this with a photo of the bilge for a second opinion. It's nice and dry at least.

[Richard10002]

Read all of this as I had much the same problem as you.... probably much rustier, and I'm a bit over a decade older

 

 

I scraped the rusty bits with a long handled scraper. Hoovered it out with a Wickes wet and dry vacuum, and painted it with Vactan with a long handled brush. It certainly looks like all of the rust has been converted to metal.

 

Just ordered Craftmaster Grey Primer and High Build Undercoat, and Light Grey Bilge Paint. We'll see how it goes.

 

 

[Guest]

1 minute ago, Richard10002 said:

Read all of this as I had much the same problem as you.... probably much rustier, and I'm a bit over a decade older

 

 

I scraped the rusty bits with a long handled scraper. Hoovered it out with a Wickes wet and dry vacuum, and painted it with Vactan with a long handled brush. It certainly looks like all of the rust has been converted to metal.

 

Just ordered Craftmaster Grey Primer and High Build Undercoat, and Light Grey Bilge Paint. We'll see how it goes.

 

 

Brilliant. Thanks very much, big help!

[Momac]

While rust in my bilge is not a risk a clean engine and bilge is a must for me. This way an leaks or other issues like belts making soot are easily spotted at an early stage. Once you have it clean and painted it really shouldn't be a great deal of hard work to keep it that way if given a wipe on a regular basis.

 

[kevinm]

If it is only surface, brown powdery rust and the bilge is usually dry, it is nothing to worry about. If you want to repair it, get a solid hand scraper and scrape the bottom plate to confirm it is only powder and not thin scale, then you could get a STIFF wire brush attachment for a power drill and clean it all back to bright metal, hoover the space out, fit a very abrasive disk to your hand grinder and rough the steel surface, then hoover out again and apply a couple of coats of Aluminium based primer, then an couple of coats of epoxy. Work the paint well into corners and weld contours but dont over apply any of the coats. Allow each coat to dry thoroughly before applying the next... Job done... You will feel great and deserve a few pints after that... 

[Guest]

That looks pretty clean!

[kevinm]

looks like zero hours....   :)

[Mariner]

Especially where rust is light, I tend to avoid rust "converters" but try and get as clean a surface as I can with the wire brush (on angle grinder) and then paint with zinc phosphate primer and then top coat. I really like Johnstone's products.

One of the rust converters that has been around for decades is Jenolite. The original product (actually called a rust 'remover') was essentially phosphoric acid which left a layer of iron phosphate on the surface, and that seem to work well on stuff that was really badly rusted. More recently, they brought out a new product called a converter and I tried that and was very unimpressed.

 

Ask ten different people and you will always get several different likes and dislikes when it comes to products to treat rust. The one thing that everybody might agree on is to wear a good face mask when you do the brushing; I find that rust dust up my nose really bugs me for days!

[Momac]

1 hour ago, kevinm said:

looks like zero hours....   :)

The engine bay was not so clean when I first bought the boat  in 2014 . However it was  not exactly a major project to get it as I wanted . Just a matter of putting in some time.

The original owners did only 205 hours in the 11 years from new in 2003 - which is extremely low . A lot of people buy motorboats and don't go far.

Since June 2014 I have added almost 400 hours - mostly on the Trent but  including some sea trips.

The photo is probably taken when the boat would have been about 13 years old. It looks just the same now. I  did spend a couple of hours cleaning the engine bay last weekend. 

I guess people who own narrowboats do a lot more hours . 

 

Edited May 3, 2018 by MartynG

[Lily Rose]

9 hours ago, MartynG said:

 

Since June 2014 I have added almost 400 hours - mostly on the Trent but  including some sea trips.

 

I guess people who own narrowboats do a lot more hours . 

 

 

It must vary hugely but for my narrowboat the engine had done 3,600 hours in 15 years when we bought it 2 years and 9 months ago. Since then we've added 616 hours. This included 300 in 2017 during the total of 4.5 months, spread across the year, we were on the boat. 

 

I wish my bilge looked like yours but unfortunately it is a bit of a mess of rust and flaky paint. But at least it's dry.

 

I bought some white Danboline for it which I haven't got round to applying yet as it really needs a good clean out first but it's so hard to get at (someone stuck an engine in the way!) that this looks pretty much impossible.

 

It probably needs the engine removing first (  like this:  https://cruisingthecut.co.uk/2018/01/31/vlog-125-utter-bilge/ ) to do it properly but that seems a bit drastic so I'll probably just learn to live with it as it is and hope that it lasts for as long as I own the boat.

 

[kevinm]

Just check the bottom plate condition of your bilge regularly, if there are pools of water sloshing around, mop it out and dry it. There are different types of corrosion, if you spot any patches of aggressive pitting you might want to consider a complete blast and repaint of the compartment. Generally speaking, scale rust is not much of a problem. 6mm thickness of scale is generally representative of 1mm of actual steel loss. Localized Pitting corrosion however is a different animal and given the correct environment, has been known to eat through 10mm of steel in 12 months.

[Dr Bob]

22 hours ago, welly said:

 As I say, the rust is pretty light and so am wondering if I could almost just apply fertan to it, let it do its job and then pour a load of red oxide primer over it?

 

How effective is fertan on light rust? Or would vactan or something else be an option? I could with a bit of effort and a small wire brush probably get into some of the cracks and crevices 

Yes, I would follow Richards post in post 2. That is my job for this summer. I've only used Fertan in the past but this is a job for Vactan as Fertan need washing off so another step of drying. Don't just pour a load of red oxide primer over it. Brush it in well to get it into the cracks and crevices. Then cover it with a bilge paint.

[jaywalker]

I have scraped the scale rust in my bilge and ordered vactan from eBay, once treated is Hammerite hammered finish paint a worthwhile option as a topcoat?

[Mariner]

On 04/05/2018 at 10:11, kevinm said:

6mm thickness of scale is generally representative of 1mm of actual steel loss. Localized Pitting corrosion however is a different animal and given the correct environment, has been known to eat through 10mm of steel in 12 months.

Can you tell us the source of your information that 1mm of steel transforms in to 6mm of scale?  If you look at Wiki to find out about Pilling-Bedworth ratio https://en.wikipedia.org/wiki/Pilling–Bedworth_ratio that tells you that one volume of iron produces about two volumes of oxide. Without doubt, rust tend to be very porous, and mixture of oxide and hydroxide, so in reality, 1 to 2 probably underestimates it ...but 1 to 6???

 

Pitting corrosion is very often the source of much grief. Pretty often, that occurs where there were minor imperfections were rolled in to the steel sheet at the mill. Not sure what you can do to avoid that in a bilge. Can sacrificial zinc anodes be used in bilges just as they are on the outside of large ocean-going vessels? I see that some narrowboat engines include sacrificial (replaceable) zinc anodes in their cooling systems.

[kevinm]

Not sure if it is written anywhere, perhaps in corrosion related papers, but 15 years of experience surveying and inspecting floating installations in the Oil and Gas Industry for Classification Societies such as Lloyds, DNV & ABS has led me to this conclusion. Yes, I stand by it...   1-6

 

Yes you can place sacrificial anodes in your bilge but they will only work when they are part or covered with water (electrolyte) and since its best to keep the bilge dry, there probably wouldnt be much point. The only place on the outer hull of sea going ships where anodes are sited is usually around the stern where the propeller causes vast amount of turbulence and therefore increases the likelihood of "cavitation corrosion." Modern hull coatings usually dictate that the primer coat in direct contact with the steel acts as the anode.

 

[Momac]

8 hours ago, Mariner said:

Can you tell us the source of your information that 1mm of steel transforms in to 6mm of scale?  If you look at Wiki to find out about Pilling-Bedworth ratio https://en.wikipedia.org/wiki/Pilling–Bedworth_ratio that tells you that one volume of iron produces about two volumes of oxide. Without doubt, rust tend to be very porous, and mixture of oxide and hydroxide, so in reality, 1 to 2 probably underestimates it ...but 1 to 6???

 

 

https://www.steelconstruction.info/Corrosion_of_structural_steel

 

 

[WotEver]

1 hour ago, MartynG said:

https://www.steelconstruction.info/Corrosion_of_structural_steel

Essentially, the iron in the steel is oxidised to produce rust, which occupies approximately six times the volume of the original material.

[Sea Dog]

14 hours ago, jaywalker said:

I have scraped the scale rust in my bilge and ordered vactan from eBay, once treated is Hammerite hammered finish paint a worthwhile option as a topcoat?

Bit susceptible to chipping I think. You'd be better off with an appropriate bilge paint - it's almost like it's made for the job!  White or light grey is favourite as it shows any leaks and it's easier to spot anything you drop.

[Dr Bob]

19 hours ago, jaywalker said:

I have scraped the scale rust in my bilge and ordered vactan from eBay, once treated is Hammerite hammered finish paint a worthwhile option as a topcoat?

I agree with Seadog. In the 12 months I have been on this forum, I have not heard much (if any) support for Hammerite. It seems a very brittle paint and although can go over unprepared surfaces, I dont think it will work as an immersion coating. Buy a bilge paint. When I do mine this year I will not use hammerite ...but likely look for a good 2 pack epoxy bilge paint - 2packs will be the best for immersion duty.

[Mariner]

16 hours ago, kevinm said:

Not sure if it is written anywhere, perhaps in corrosion related papers, but 15 years of experience surveying and inspecting floating installations in the Oil and Gas Industry for Classification Societies such as Lloyds, DNV & ABS has led me to this conclusion. Yes, I stand by it...   1-6

As others have shown, there is certainly at least one website where the figure of 6 is quoted, but the vast majority of other sources claiming more typical values of around 2. Of course rust composes of different forms of iron oxide, together with hydroxide, but I have spent quite some time on the web and cannot find single peer-reviewed paper, or a published referring to PB=6.

 

My own background is in the British Nuclear Industry. As you may know, the first generation of reactors in the UK (the "Magnox") ran in to very serious problems of "anomalous oxidation" of mild steels, and very soon after they were put in to service, all of the stations had to be run with their operating temperatures turned down by about 30%, with corresponding loss of power output (seriously bad news!). The problem had never showed up in the development work done before construction, and I'm not sure if anyone ever figured out why the problem occurred in-reactor. This was a problem related to oxidation rate rather than PB.

[Guest]

Had a dabble this morning, scraped away enough rust that it felt like fertan could get to work. I'll have a look in the morning and see how it is. Looked to have started converting almost within an hour though. ?

 

Next question is what next? Red oxide paint and the bilge paint or can I can just use normal boat paint over the red oxide? Or should I not be using red oxide paint in the bilge at all?

 

Cheers!

[Richard10002]

I have treated mine with Vactan, and can see that it has worked. However, it's taken me so long to get round to painting that a few tiny specks of rust are reappearing, so I'll be vactan'ing it again before painting.

 

I've bought Craftmaster Primer, High Build Undercoat, and Bilge Paint. I bought direct but, if I was buying again, I would revert to buying from a stockist and collecting... even though I have an hours round trip to collect, and may have to wait a bit for their delivery.

 

Without going into too much detail, a tin had leaked in the box, causing a real mess, and we were lucky it didnt spill over into the house. Apparently, a shelf of some kind had fallen over at the couriers depot, thus damaging 3 tins. Craftmaster tell me that this almost never happens and, whilst I believe them, I wont be risking it again. Thorn Marine at Stockton Heath for me in the future.

[Dr Bob]

3 hours ago, welly said:

Had a dabble this morning, scraped away enough rust that it felt like fertan could get to work. I'll have a look in the morning and see how it is. Looked to have started converting almost within an hour though. ?

 

Next question is what next? Red oxide paint and the bilge paint or can I can just use normal boat paint over the red oxide? Or should I not be using red oxide paint in the bilge at all

If you bilge is normally dry then that looks an ok system. If it is often wet and therefore the paint is under water, then a better system might be more appropriate...i.e.  a 2 pack epoxy designed for us in bilges plus a primer if recommended. 2 pack epoxies will be better for immersion duty but not needed if no immersion.

I will likely do mine with your suggestion as my bilge is dry.

[Richard10002]

My engine hole bilge got wet because the bilge pump failed and I didn't get round to replacing it, (have now), coupled with the drainage channels under the panels on the cruiser stern being allowed to get clogged up.

 

Hopefully, now that I'm on the case, it wont happen again.....

 

[Sea Dog]

7 hours ago, Richard10002 said:

My engine hole bilge got wet because the bilge pump failed... 

 

Point of order m'lud!  Your bilge got wet because water came in, not because it didn't subsequently get pumped out.