Rust repairs

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purple5ive
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Re: Rust repairs

Post by purple5ive » Wed Apr 08, 2020 10:59 am

hornet wrote:
Wed Apr 08, 2020 10:49 am
Nude up wrote:
Wed Apr 08, 2020 10:25 am
hornet wrote:
Wed Apr 08, 2020 10:15 am
Nude up wrote:
Wed Apr 08, 2020 9:46 am
If you do use duralac wear gloves it is a chromate and is absorbed through your skin that said it is one of the best things to stop dissimilar metal corrosion widely used in the aviation industry. Ps I use it a lot on my boat an example the zinc trim tab anode and stainless bolt assemble with duralac remove in 5 years no issue.

The yellow is chromate the green does not contain chromate we use both at work but everyone uses gloves read the sds.
Caution Nudie I wouldn't cote the anodes with anything...anodes are suppose to decay... if they don't decay your engine is corroding internally, I'm in the outboard trade.
Only the thread of the bolt is coated it’s like tooth paste only the thread of the anode is in contact with the paste
It is still a contact point for the anode to do it's job, nothing the anode comes in contact with should be coated that restricts transfer, that includes bolts that hold them in place,if anything some engine oil so they thread in smoothly but will not interfere with metal to metal contact.
Correct, basic law of science, Sacrificial anode.
its only sacrificial if its in contact with the part its meant to save, otherwise its just another useless ornament.

also painting the anode is another strict NO NO!!!

For the anode to work, its needs to be in contact with the metal its protecting, as well as the saltwater its being used in.

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Andrews
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Re: Rust repairs

Post by Andrews » Wed Apr 08, 2020 11:30 am

Aluminum corrosion is unavoidable on a tinny, but the dull white aluminum oxide forms a protective coating helping prevent the metal form corroding further. Pitting is the greatest concern with aluminum and the formation of either holes or growths on the surface due to the displacement of material. That rust is an iron oxide, from the screws which contain an iron alloy.

What is everyone opinion on a sacrificial anode on an aluminum boat?

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hornet
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Re: Rust repairs

Post by hornet » Wed Apr 08, 2020 11:38 am

TAKEN FROM: https://www.boataccessoriesaustralia.co ... at-anodes/

Electrolytic Corrosion – Damaged appliances or wiring that is leaking current to ground via the hull (metallic hulls) or via common earth to submerged metal causes what's known as electrolytic corrosion. This can also rot bearings, washers, oil and water coolers and cause major engine damage quickly.

Galvanic Corrosion – Relies on two dissimilar metals connected and in the same electrolyte (sea water). The two metals act like a battery, with some amount of electrons flowing between the two that leads to one of them giving up metal ions to the seawater.


Zinc Anodes – Zinc is traditionally cheaper and more commonly used than aluminum used for sacrificial anodes that have lower electrons to dissolve to protect the more valuable metal parts of a boat.

Aluminum Anodes – Suitable for outboard motors due to its ability to form a protective oxide surface film with good corrosion resistance but also prone to galvanic corrosion when in contact with more noble metals like bronze, brass or nickel.

Boat & Marine Material

Boat Hull Materials differ in their corrosiveness based on the materials. Fiberglass and wood hulls are not susceptible to corrosion however the equipment attached to it are, such as propellers and outboard equipment.

Aluminum and steel hulls are susceptible to galvanic corrosion. Aluminum on its own does quite well in both fresh and salt water but when combined with other metals it will start to corrode. Usually a protective paint coating can provide a high electrical resistance barrier between the aluminum and water although in some cases employing dedicated sacrificial anodes can be useful.
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Re: Rust repairs

Post by SteveoTheTiger » Wed Apr 08, 2020 12:46 pm

Andrews wrote:
Wed Apr 08, 2020 11:30 am
What is everyone opinion on a sacrificial anode on an aluminum boat?
When i had my tinny i only had the one on the outboard. I just made sure that anything i installed was done properly and that i didnt drop any hooks or sinkers under the floor.. or if i did i picked them up ASAP.
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hornet
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Re: Rust repairs

Post by hornet » Wed Apr 08, 2020 1:15 pm

SteveoTheTiger wrote:
Wed Apr 08, 2020 12:46 pm
Andrews wrote:
Wed Apr 08, 2020 11:30 am
What is everyone opinion on a sacrificial anode on an aluminum boat?
When i had my tinny i only had the one on the outboard. I just made sure that anything i installed was done properly and that i didnt drop any hooks or sinkers under the floor.. or if i did i picked them up ASAP.
When bought my used tinny first thing I did was rip up the old floor, I found just one round sinker wedged on a strut, I got it out with pliers and found a tiny little hole developing, I sanded it back used a blind rivet and sealed it with sikaflex, I was lucky the hole had just started but it did go right through the hull, if it was there for a number of months I'm sure it would have progressed into a larger area what we call "pitting" in the trade.
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russellh2
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Re: Rust repairs

Post by russellh2 » Wed Apr 08, 2020 1:37 pm

Quoted $500 to fix is an absolute rip-off.
Anyone with reasonable mechanical skills could do this job, it is fairly simple.
Google "replace boat drain bung assembly" for videos etc.
If you are not comfortable doing it yourself see if a friend or your local mechanic can drill out the rivets for you. When rivets drilled out buy what you need to clean the effected area - See above posts, and buy 316 stainless nuts & bolts plus sealant, paints, cleaning materials etc, use "wet and dry" in place of sandpaper.
$500 = 3.333 hours @ $150/hour ? ? ?

Also your location - Maybe there is a member close to you who can assist

Bugatti

Re: Rust repairs

Post by Bugatti » Wed Apr 08, 2020 1:48 pm

All very good advice given, Pdiddy

Brett wrote:
Wed Apr 08, 2020 8:51 am

It's the rivet inserts that are rusting, replacethe rivets with stainless nuts and bolts and coat the bolts in duralac
Brett's smack bang on the money.

People think that Aluminium Rivets don't rust, they don't BUT the anvil insert that stays with the rivet does as it is only mild steel.

I don't use rivets on my Boat, they can't be "serviced"/taken off easy.
And a big no no, is never rivet plastic to anything. The force of the rivet popping can crack, break the plastic.

Rivet.JPG
Rivet.JPG (14.4 KiB) Viewed 1476 times


Rivet 1.JPG


re-tyred wrote:
Wed Apr 08, 2020 8:07 am
get new bung inserts and start again with 316 stainless. Sikaflex around the new ones before screwing them into the hull. Tefgel the threads of the new stainless steel bolts.
This is a very important job. You don't want them to fail and they will be adding to other corrosion on the hull.
And as re-tyred said. Always use 316 stainless bolts and as Brett showed, get them from Witworths. you can bag up as many or as little as you want without buying a pack of 10 just to use 2.
Oh, and always use nyloc nuts, they are worth the extra couple of cents.

Screws are an easy way (a cheats way) to "fix" something to something but in a marine application, the threads of the parent material with corrode and the screw won't grab as well in the long run. Plus screws into fibreglass chips and is messy. Always use bolts. Round headed (preferably philips head), or hex head bolts. 3/8 " bolts are a handy size and just a little larger than your standard rivet.


Bolts.JPG

Sikaflex.JPG

With Sikaflex, I use tooth picks or ear cleaners to apply it to fiddly bits (no not my fiddly bits :-D ) and use toilet paper (if you can find :-D some :rf: ) as you can throw it away with each wipe, instead of a rag that just gets loaded with sikaflex wiping and gets messy. Turps or thinners dampened on a rag is great for final wipe down.

Pdiddy all the advice on this thread by the members is very valuable, should give you plenty of info to protect your ride


Cheers, Bugs

Bugatti

Re: Rust repairs

Post by Bugatti » Wed Apr 08, 2020 1:52 pm

russellh2 wrote:
Wed Apr 08, 2020 1:37 pm
Quoted $500 to fix is an absolute rip-off.
Anyone with reasonable mechanical skills could do this job, it is fairly simple.
Google "replace boat drain bung assembly" for videos etc.
If you are not comfortable doing it yourself see if a friend or your local mechanic can drill out the rivets for you. When rivets drilled out buy what you need to clean the effected area - See above posts, and buy 316 stainless nuts & bolts plus sealant, paints, cleaning materials etc, use "wet and dry" in place of sandpaper.
$500 = 3.333 hours @ $150/hour ? ? ?

Also your location - Maybe there is a member close to you who can assist
Agreed

If you have the time, it's all work you can easily do yourself with a bit of research. Plus you can go over ALL your Boat and you get to know the ins and outs of it all. A bit of elbow grease and a few trips to Witworths , , , , bingo , , , , is your nameo :tu:

Notwithstanding any Ali Welding that might need to be done.


Cheers, Bugatti

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hornet
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Re: Rust repairs

Post by hornet » Wed Apr 08, 2020 2:00 pm

I use these rivets, no steel shaft left after put in place all aluminum closed head, no corrosion at all.

Image
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ben475
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Re: Rust repairs

Post by ben475 » Wed Apr 08, 2020 2:31 pm

going by the photo's it looks like the centre of the rivets have rusted. aluminium rivets from Bunnings etc still have a steel centre and will rust out.
you need to track down some fully aluminium rivets made for use in marine applications. it will be easy to get the wrong ones.
i'm not exactly sure where you will find the ones you need but i'm told they exist.

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