In this video we finish cleaning and repairing our entire raw water cooling system - from the seacock which lets the water in, to the exhaust outlet where it returns to the sea. It's taken us a month to complete and now I finally get MY BED BACK. Jim also repairs the Perkins marine Heat Exchanger with Devcon Epoxy Aluminium Putty. We're mobile again and our entire marine engine raw water system is as good as new!
Here is some more technical information about the job for those who may be considering tackling a similar project or just interested:
Oxidation on aluminium surfaces reduces the adhesion of epoxies and it must be removed before using the Devcon Aluminum Putty or any similar product. It can be removed either by mechanical means or chemical means. In this case I used a combination of the two with materials easily accessible for most boat owners. The full process was:
1. Drum sander to clean up & reduce the two (curved) pitted surfaces.
2. Rotary wire brushing with stainless wire to further penetrate into the ‘pits’.
3. Hand wire brushing with coarse then finer stainless wire brushes, focusing on the pitted surfaces, digging the wires into the pits.
4. The pits were then then targeted with Phosphoric acid (the Barnacle Buster Concentrate) diluted 2:1 with water and a toothbrush. Allowed to sit for 5 mins then thoroughly rinsed with water. Then repeat with a 1:1 Barnacle Buster Concentrate/Water solution.
5. The entire heat exchanger was then acid etched by immersing in a tub with weak Phosphoric acid solution (the Barnacle Buster Concentrate diluted about 1:15 with water) for about 30 minutes.
6. The acid solution was then drained and a hose inserted into the coolant cavity of the HE. The hose was run for about 30 minutes, forcing water flow through all the cavities to rinse the HE, thus filling the tub and allowing it to overflow. So the HE was both immersed and had water flowing through it to remove any traces of acid. We did it this way because we had unlimited water but if aboard a boat you could skip this step and go to step 7.
7. We added about 500gm of Bicarbonate of Soda powder to the tub of water to further passivate any residual acidity. After about 30 minutes in the bicarbonate solution, the HE was again thoroughly rinsed. Ensure that you flush the cavities thoroughly as well.
8. Once drained and dry the HE was heated with a portable gas flame to accelerate drying. The areas where the Devcon was to be applied were targeted to sweat out any moisture. I used a weed killer torch that burns gas at about 1900 C. In this case the repair areas only had engine coolant running through them (not sea water) so there was no real need to sweat the metal with the torch to remove impurities but it was a good extra step to dry it thoroughly. If the area to be repaired had been exposed to sea water it would need the flame sweating and cleaning at least twice to ensure any impurities have been removed.
The above process achieved a clean, acid etched surface. The pits had the appearance of bare alloy with no oxidation or contamination. Another option would have been to grit blast the pitted surfaces but I was satisfied with the surface we achieved.
How strong is the Barnacle Buster Concentrate?
The MSDS says it’s approx 50% Phosphoric Acid and the recommended dilution rate is 1:4
So using 100ml of Barnacle Buster Concentrate to make a 500ml working solution will result in the following mixture contains 100ml of Barnacle Buster Concentrate contains 50ml of H3PO4 (Phosphoric acid) plus 50ml of H₂O (Water), so a 1:4 solution contains:
(50 ml of H3PO4 + 50 ml of H₂O) + 400 ml of H₂O to make a 500ml solution
= a 10% Concentration of Phosphoric Acid
Corrosion Resistance of Copper and copper Alloys
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(This video is about sailing, boating, how you boat's raw water system can block and why, what happens when the raw water or cooling system on your boat gets blocked, how to flush it and maintain it, how to use Barnacle Buster safely and effectively, how to clean and repair your heat exchanger, test that it is working properly and refit it. We replace our wet exhaust synthetic hose after it was overheated and we fit a new non return valve in the exhaust system).
MB654606984D
11 сен 2024
