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Author Topic: electrolitic corrosion  (Read 6947 times)

dieselgman

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Re: electrolitic corrosion
« Reply #15 on: December 03, 2006, 07:03:50 AM »
We work mostly on high-speed diesels - Detroit Diesel, Caterpillar and the like. The SCA coolant additive is a critical maintenance issue due to cavitation and corrosion issues in the cast iron parts. It is something you can monitor easily with a litmus-type test strip that you dip into the coolant and compare with a chart to determine ppm of the nitrite component in the additive. It is important to avoid too high a concentration because of unwanted deposits in hot-spots in the engine which degrade cooling performance. Some of these engines have been known to self-destruct in the absence of such protection.

I was also wondering about cavitation issues with the slow-speed Lister diesel and whether there was anyone with enough run-time on their equipment to be able to tell. My uneducated guess would be that the slow-speed Lister would not generate the vibration frequencies to produce the destructive cavitation bubbles in the coolant. Has anyone investigated this?

Gary
diesel-electric.us
ALL Things Lister/Petter - Americas
Lyons Kansas warehousing and rebuild operations

listerdiesel

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Re: electrolitic corrosion
« Reply #16 on: December 03, 2006, 09:18:14 AM »
One of our chargers is used on the GM Canada loco which is called a 'Class 66' in the UK. There is also a faster version called the 'Class 67'.

The battery connector is made by a company called Pyle National, part of Amphenol.

The charger connector body has a mixture of brass, plated steel and aluminium (aluminum) parts, and within almost days it is almost impossible to disassemble as there is galvanic corrosion between the parts. Took one out of the box the other day (we are shipping a couple of chargers up north tomorrow) and it had already started to seize up. The other thing that bugs me is that they will use fine threads on these parts of the body that have to come undone, and of course they don't...

We make our own charger connectors now, out of solid stainless steel, and avoid any such problems. We haven't cloned the Pyle unit yet, but the condition they get into in outdoor railway use has to be seen to be believed! This is a part that they quote $US500.00 each for.

Peter 


Doug

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Re: electrolitic corrosion
« Reply #17 on: December 04, 2006, 03:26:06 AM »
Another interesting thing that happens under those conditions Peter is something called racheting....
Parts actualy seperate due to thermal stress pushing and pulling the oxides between the different metals.

Then there's a condition that some times happens with metals alloying with each other and oxides.

I won't pretend to understand the mechanics of this but in a hot humid corrosive enviroment like where I work this happens fast unless you use the right connectors and compound.

Doug