Author Topic: Rust removal with acid  (Read 569 times)

Offline Canuck750

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Rust removal with acid
« on: July 02, 2022, 11:01:23 AM »
I am helping a friend get a 1975 GoldWing back on the road after a very long slumber. One of the side jobs is making the bike a bit more presentable, removing the rust bloom from non painted parts. The GoldWing muffler is a huge one piece unit with bolt on flashes of chrome each side, underneath its black painted steel.
After warming the bike up we mixed muriatic acid 1:1 with water and using a small trim paint brush soaked the hot muffler with the solution. In minutes the acid dissolved a very thick coating of rust. It is amazing to see how fast the acid combined with heat cleans the old muffler to shiny steel.
Finish with header paint and looks great.

Brushing the solution on the frame will not damage paint but is gets the rust off quick so that a brush on coat of Por-15 satin black can freshen the frame.

Try and keep the acid off chrome for any length of time as it can discolour the chrome.

Works great on rusty fasteners as well, just brush clear coat over the bolts and nuts once the acid has done its work.

Make sure to do this outside in a well ventilated area and wear rubber gloves. Keep a hose near by to neutralize the acid .
48 Guzzi Airone, 57 Guzzi Cardellino, 65 Benelli 200 sprite, 66 Aermacchi Sprint, 68 Gilera 106 SS, 72 Eldorado, 72 Benelli 180, 74 Guzzi 750S, 73 Laverda SF1, 74  Benelli 650S, 75 Ducati 860GT, 75 Moto Morini 3-1/2, 78 Moto Morinii 500

Offline moto-uno

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Re: Rust removal with acid
« Reply #1 on: July 02, 2022, 02:36:35 PM »
  Probably my favourite method to de-rust parts , would add goggles as a necessary protection  :thumb: . Peter

Offline Canuck750

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Re: Rust removal with acid
« Reply #2 on: July 02, 2022, 07:26:29 PM »
Probably best to neutralize the acid with a base solution then wash and add protective coating.

Any before, during and after pics?

sorry I didn't even think of taking some pictures while I was cleaning the frame and muffler.

we washed the frame and muffler down with a soapy power washer and then rinsed and dried.
48 Guzzi Airone, 57 Guzzi Cardellino, 65 Benelli 200 sprite, 66 Aermacchi Sprint, 68 Gilera 106 SS, 72 Eldorado, 72 Benelli 180, 74 Guzzi 750S, 73 Laverda SF1, 74  Benelli 650S, 75 Ducati 860GT, 75 Moto Morini 3-1/2, 78 Moto Morinii 500

Offline SIR REAL ED

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Re: Rust removal with acid
« Reply #3 on: July 02, 2022, 08:30:11 PM »
I am helping a friend get a 1975 GoldWing back on the road after a very long slumber. One of the side jobs is making the bike a bit more presentable, removing the rust bloom from non painted parts. The GoldWing muffler is a huge one piece unit with bolt on flashes of chrome each side, underneath its black painted steel.
After warming the bike up we mixed muriatic acid 1:1 with water and using a small trim paint brush soaked the hot muffler with the solution. In minutes the acid dissolved a very thick coating of rust. It is amazing to see how fast the acid combined with heat cleans the old muffler to shiny steel.
Finish with header paint and looks great.

Brushing the solution on the frame will not damage paint but is gets the rust off quick so that a brush on coat of Por-15 satin black can freshen the frame.

Try and keep the acid off chrome for any length of time as it can discolour the chrome.

Works great on rusty fasteners as well, just brush clear coat over the bolts and nuts once the acid has done its work.

Make sure to do this outside in a well ventilated area and wear rubber gloves. Keep a hose near by to neutralize the acid .

Excellent idea.  I think this would be a great way to touch up a motorcycle frame I have.  I don't want to do a complete tear down just to freshen up a few spots on the frame and engine.  Localized clean up with acid never occurred to me.

I thought that satin black paint would be a good match for the original gloss black paint that is 40 years old and no longer shiny.

Thanks.
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Re: Rust removal with acid
« Reply #3 on: July 02, 2022, 08:30:11 PM »

Offline SIR REAL ED

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Re: Rust removal with acid
« Reply #4 on: July 02, 2022, 08:46:23 PM »
Hey Canuck,

I don't see a satin black paint on POR-15's web site.  Is chassis black a satin finish?  Thanks.
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Offline Dirk_S

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Re: Rust removal with acid
« Reply #5 on: July 02, 2022, 08:48:53 PM »
I remember looking into the muriatic acid/ hydrochloric acid idea for chrome and stainless steel pipes once or thrice. While the results of many a pipe Iíve seen look absolutely magical, there were lots of folks needing caution or straight up advising against using the acid, as over time it eats into the metal regardless of how fast you think you got it off. It was enough to scare me away, but maybe one day Iíll give it a go on these stainless aftermarket pipes.
« Last Edit: July 02, 2022, 08:49:21 PM by Dirk_S »
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Offline Canuck750

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Re: Rust removal with acid
« Reply #6 on: July 02, 2022, 08:52:28 PM »
POR-15 in a can will brush on very easily, it flows to a near flat surface if you use a good quality trim brush, I just buy a good quality, very small brush from Home Depot. The spray cans are good quality but you need to mask carefully, this stuff is very hard to get off of any surface including your skin! Lacquer thinner will clean up spills or drips.

POR-15 is not UV resistant without a clear top coat but for frames I don't bother with a top coat. The gloss black is very shiny and I don't think its a good match for most frames.

A pretty tired looking Laverda frame, I ran 220 grit dry paper over the rough original paint, acid washed the frame, neutralized it and brush painted POR-15, I did a LOT of masking but I did not disassembled the whole bike, motor stayed in the frame.

I removed what was practical and powder coated the center and side stands, fork lowers, foot rest brackets, swing arm and misc parts that were easy to remove.

I did this to see if POR-15 was practical to do as opposed to Powder coating, truth be told I only went this route on one restoration but it was satisfactory



painted frame



one the body work is back on, the eye doesn't pay much attention to a frame provided its not chipped and rusty, plus so little of the frame is visible



« Last Edit: July 02, 2022, 08:58:09 PM by Canuck750 »
48 Guzzi Airone, 57 Guzzi Cardellino, 65 Benelli 200 sprite, 66 Aermacchi Sprint, 68 Gilera 106 SS, 72 Eldorado, 72 Benelli 180, 74 Guzzi 750S, 73 Laverda SF1, 74  Benelli 650S, 75 Ducati 860GT, 75 Moto Morini 3-1/2, 78 Moto Morinii 500

Offline Canuck750

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Re: Rust removal with acid
« Reply #7 on: July 02, 2022, 08:55:55 PM »
Hey Canuck,

I don't see a satin black paint on POR-15's web site.  Is chassis black a satin finish?  Thanks.

Yes, 'Chassis Black' Direct to Metal Top Coat is what I usually use.
48 Guzzi Airone, 57 Guzzi Cardellino, 65 Benelli 200 sprite, 66 Aermacchi Sprint, 68 Gilera 106 SS, 72 Eldorado, 72 Benelli 180, 74 Guzzi 750S, 73 Laverda SF1, 74  Benelli 650S, 75 Ducati 860GT, 75 Moto Morini 3-1/2, 78 Moto Morinii 500

Offline Canuck750

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Re: Rust removal with acid
« Reply #8 on: July 02, 2022, 09:00:04 PM »
I remember looking into the muriatic acid/ hydrochloric acid idea for chrome and stainless steel pipes once or thrice. While the results of many a pipe Iíve seen look absolutely magical, there were lots of folks needing caution or straight up advising against using the acid, as over time it eats into the metal regardless of how fast you think you got it off. It was enough to scare me away, but maybe one day Iíll give it a go on these stainless aftermarket pipes.

I would stay away from trying to clean chrome plating with acid, and acid will remove a zinc coating very quickly. I think the acid should be restricted to carbon steel oxide.
« Last Edit: July 02, 2022, 11:18:23 PM by Canuck750 »
48 Guzzi Airone, 57 Guzzi Cardellino, 65 Benelli 200 sprite, 66 Aermacchi Sprint, 68 Gilera 106 SS, 72 Eldorado, 72 Benelli 180, 74 Guzzi 750S, 73 Laverda SF1, 74  Benelli 650S, 75 Ducati 860GT, 75 Moto Morini 3-1/2, 78 Moto Morinii 500

Offline Scout63

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Re: Rust removal with acid
« Reply #9 on: July 02, 2022, 09:42:30 PM »
Great thread.
Ben Zehnder - Orleans, MA USA
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Offline SIR REAL ED

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Re: Rust removal with acid
« Reply #10 on: July 03, 2022, 08:09:56 AM »
Yes, 'Chassis Black' Direct to Metal Top Coat is what I usually use.

Mucho thanks Sensei!
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Offline Chuck in Indiana

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Re: Rust removal with acid
« Reply #11 on: July 03, 2022, 08:19:28 AM »
I would stay away from trying to clean chrome plating with acid, and acid will remove a zinc coating very quickly. I think the acid should be restricted to carbon steel oxide.

For rust on chrome plating.. aluminum foil and water. Trust me on this one, it doesn't sound as if it would do anything.
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Offline SIR REAL ED

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Re: Rust removal with acid
« Reply #12 on: July 03, 2022, 08:24:04 AM »
Yes, 'Chassis Black' Direct to Metal Top Coat is what I usually use.

Have you tried using any of their engine paint in a brush on mode on a motorcycle engine?
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Offline yogidozer

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Re: Rust removal with acid
« Reply #13 on: July 03, 2022, 08:30:31 AM »
Acid never helped Ozzy  :shocked:



Offline Canuck750

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Re: Rust removal with acid
« Reply #14 on: July 03, 2022, 10:18:02 AM »
Have you tried using any of their engine paint in a brush on mode on a motorcycle engine?

I have not, but I bet it is a very good if itís anything like the chassis paint.

Thanks Clint, I agree that motorcycle alloy parts were never finished to a fine mirror shine, the side covers I poslihed are probably shinier than they ever left the Pessaro factory.
« Last Edit: July 03, 2022, 01:59:07 PM by Canuck750 »
48 Guzzi Airone, 57 Guzzi Cardellino, 65 Benelli 200 sprite, 66 Aermacchi Sprint, 68 Gilera 106 SS, 72 Eldorado, 72 Benelli 180, 74 Guzzi 750S, 73 Laverda SF1, 74  Benelli 650S, 75 Ducati 860GT, 75 Moto Morini 3-1/2, 78 Moto Morinii 500

Offline sign216

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Re: Rust removal with acid
« Reply #15 on: July 05, 2022, 07:21:17 AM »
For rust on chrome plating.. aluminum foil and water. Trust me on this one, it doesn't sound as if it would do anything.

A more effective version is bronze wool.  They have it for ships in hardware stores near the coast. 

Bronze is harder than aluminum.  Not as hard as steel wool, but the metal traces it leaves behind won't rust, like steel will.
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