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Author Topic: Paint Removal LPW  (Read 765 times)

Robert

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Paint Removal LPW
« on: January 09, 2022, 11:05:05 PM »
Iíve broken down my engine and removed all the grey paint from the aluminium parts of my engine. I thought this was going to be the tricky part. I am now onto the iron head and block but having difficulty getting the red undercoat/primer off underneath the grey. Iím planning to paint with POR15 engine enamel. Does anybody have any suggestions to get it down to bare metal?

cobbadog

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Re: Paint Removal LPW
« Reply #1 on: January 10, 2022, 03:09:48 AM »
There are many paint strippers available from liquids to gels then hit it with the gurney. I have not used POR15 before but I am aware that it is a very good product. Is it a coloured POR15 you will be using, if so the red oxide may not harm the bond. I once had success using a can of oven cleaner, again dilute with plenty of water after use.
After having a tractor wet sand blasted they put some hydrochloric acid in the rinse water to slow down the surface rust after blasting. This gave me 2 days before surface rust started.
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dax021

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Re: Paint Removal LPW
« Reply #2 on: January 10, 2022, 05:56:15 AM »
Was it not phosphoric acid, which is the active ingredient in most rust converters?  I use hydrochloric (pool acid) to remove surface rust, but unless neutralised with an alkaline or plenty fresh water, it starts rusting almost immediately. Just my 2c, I could be wrong.

When restoring old petrol bowsers, I would completely immerse all the cast iron bits in a strong solution of caustic soda.  Not a trace of paint or primer left behind.  Just make sure there are no non ferrous metals still attached, as it will quickly chow that up.  Again, rinse well before painting, and paint asap, as it starts to surface rust very quickly.
« Last Edit: January 10, 2022, 06:03:43 AM by dax021 »

Robert

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Re: Paint Removal LPW
« Reply #3 on: January 10, 2022, 09:48:55 AM »
I have found somewhere locally that can vapour blast it. What I would like to do is to get it vapour blasted then rebuild at my leisure - I am not the fastest worker and it may take a couple of months! But I donít want it to be rusty when I finally paint it. Any ideas? Can I coat it with wd40? What to people do?

cobbadog

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Re: Paint Removal LPW
« Reply #4 on: January 10, 2022, 10:50:01 AM »
Yes dax, you are correct, my mistake and I appologise for misleading the group.

Once the metal has been cleaned you cannot treat it with an oil or anything else as it will not allow your paint or in this case POR15 to bond to clean metal.
Read the instructions on the POR15 to see if they recommend any pretreatment undercoat/primers. Otherwise wait until your ready to do the POR15. You are aware that POR15 has a very short shelf life. Once the can is opened you are all systems go and have a couple of days at most to finish using the product as once the air gets to it the curing starts. They are sealed at the factory using a gas to stop curing.
I have seen but not used a laser blaster used for motor parts. I only last night asked a member from another Forum if he has received his and if it actually worked. Like so many things the videos make you think that this is the answer to cleaning parts up but can come back and bite you. The one in question was less than AU$50.00 plus postage so will be interesting to see how it went if at all.
If there is no information on the can of POR15 send the company an email and ask if they recommend a product but it will not be any oil base products as paint and coating do not stick to oil. If you are hindered in being able to do a full days work due to health or other reasons I would suggest that you get someone to help you complete the POR15 job in one go.
« Last Edit: January 10, 2022, 11:06:15 AM by cobbadog »
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Hugh Conway

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Re: Paint Removal LPW
« Reply #5 on: January 10, 2022, 07:13:34 PM »
IIRC, used TSP mixed in a 1/2 plastic 55 gal barrel of hot water to strip my Lister and Listeroid parts. Just let it sit overnight, stirred a few times. Hosed off most of the paint the next afternoon. Was easy and inexpensive. I see similar on youtube but with a propane burner heating the water in a metal tub. Probably hotter is better, but my method worked OK for me.
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dax021

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Re: Paint Removal LPW
« Reply #6 on: January 10, 2022, 07:56:30 PM »
Yes dax, you are correct, my mistake and I appologise for misleading the group.

Once the metal has been cleaned you cannot treat it with an oil or anything else as it will not allow your paint or in this case POR15 to bond to clean metal.
Read the instructions on the POR15 to see if they recommend any pretreatment undercoat/primers. Otherwise wait until your ready to do the POR15. You are aware that POR15 has a very short shelf life. Once the can is opened you are all systems go and have a couple of days at most to finish using the product as once the air gets to it the curing starts. They are sealed at the factory using a gas to stop curing.
I have seen but not used a laser blaster used for motor parts. I only last night asked a member from another Forum if he has received his and if it actually worked. Like so many things the videos make you think that this is the answer to cleaning parts up but can come back and bite you. The one in question was less than AU$50.00 plus postage so will be interesting to see how it went if at all.
If there is no information on the can of POR15 send the company an email and ask if they recommend a product but it will not be any oil base products as paint and coating do not stick to oil. If you are hindered in being able to do a full days work due to health or other reasons I would suggest that you get someone to help you complete the POR15 job in one go.

Absolutely no need to apologise.  There are so many types of acid out there with long chemical names, it is easy to get them mixed up.  Hugh, I am unfamiliar with TSP, what is that?  I'm sure there are millions of products out there to strip paint, most of them pricy, but to be honest, for cast iron I found good old cheap caustic soda flakes(sodium hydroxide) to be the most effective.  It also works better if heated, but I never bothered, it worked perfectly albeit a bit slower at room temperature.  It will anyway get quite hot as a result of the chemical reaction with the water.  As mentioned, a couple of days completely submerged and then blasted off with a high pressure cleaner did wonders for me.  It does however, not remove powder coating or plastic based paints, these are best removed with a blowtorch.  If you are worried about rust, heat the lump up after rinsing, best in an oven, but I don't have one of those, so just used a blowtorch.  The tiny bit of surface rust that appears is easy to wire brush off just before painting.  I just used a good quality automotive primer and paint, and most of the pumps I did are showing no signs of rust after 20 plus years in the elements on farms and trucking yards.

Robert

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Re: Paint Removal LPW
« Reply #7 on: January 10, 2022, 09:24:36 PM »
Thank you for all the advice. I visited the vapour blaster today and he is a specialist in maintaining top rally cars. He reckons vapour blasting will not remove paint but offered to use grit but said I could have a problem with contamination. He said if the paint is sound donít take it off but scothbrite it to key it (he gave me a sample) and paint over it. He showed me an engine he had done like this and it looked very good. He just used Halfords engine enamel with a brush
Cobbadog thank you for the advice re the POR15 I wasnít aware of the short life.
Dax and Hugh. I have used caustic dips on wooden furniture and it was brilliant if messy. My problem is I only have a small shed and yard and havenít really the room.
As an aside I worked in the North Sea for ODECO. We used caustic in the drilling mud and some water dripped on flakes trapped in a grill above me and burnt my back! I found out after the event when I went to bed
I think I will go the scotch brite way as the paint is quite sound. It was suggested not to worry too much about masking as the paint can be scraped off before it is too hard
As with all these jobs I am discovering there are more problems than I envisaged! Thank you all

38ac

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Re: Paint Removal LPW
« Reply #8 on: January 10, 2022, 09:37:24 PM »
TSP is Trisodium  Phosphate a heavy duty cleaner.

I am not  a safety nark but anyone fooling with caustic should be wearing plenty of PPE and eye protection is mandatory.  I used to have a large heated tank that I placed Listeroids  in to rid them of paint and filler but after a couple  splashes and burns I decided uto pull the plug on that and blast them with slag.
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cobbadog

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Re: Paint Removal LPW
« Reply #9 on: January 10, 2022, 10:50:34 PM »
I forgot about the use of caustic soda flakes and I even have a small tub of them here. Basically that is all oven cleaner is only a bit milder.
Yes PPE is always a good idea in this time of not taking responsibility for our own actions and want to blame someone else.
I followed up on the laser blaster and the guy said that it has not arrived as yet and fears he has been scammed, oops!
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dieselgman

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Re: Paint Removal LPW
« Reply #10 on: January 21, 2022, 07:51:39 PM »
Heated sodium hydroxide (180 degrees F) in water is best for stripping cast iron hot-tank style. Not recommended for aluminum alloy, but there are also buffered versions on the market for that application as well.
We often leave the original red primer in place after all other paint and contamination has been released and rinsed from parts.

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Robert

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Re: Paint Removal LPW
« Reply #11 on: January 22, 2022, 05:01:53 PM »
Thanks thatís what I intend to do. Iíve got some 3M scotchbrite to scuff the red primer.