Hot Rods Galvanic Corrosion

How can I stop galvanic corrosion? This is the second Mr. Gasket thermostat housing that I need to replace. There is a hole that I can put my finger thru. After the first housing failed I purchased a radiator cap with a zinc anode, but the thermostat housings still get corroded away. The last thing I need is to be stuck on the road with a massive coolant leak. Would additional grounds help?

 

Chrome plated steel?

 

Are you using distilled water or tap water?

 

Also you didn't say what engine you are playing with. Your avatar is a ford so I will assume it is still SBC, I use the GM aluminum t-housing. The one on my 69 Camaro is 50 years old and works fine.

 

Sounds like poor or no antifreeze or cheap chinese pot metal.

 

Theres no Galvanic Corrosion, what you have is rust through. I guarantee you Mr. Gasket thermostat housings are cheap steel and made in China. You only get about a years use before they rust through.
I only use aluminum GM housings.

 

I'm betting Mr Gasket housings are zinc as in pot metal.
I have sacrificial zincs on my aluminum outdrive on my boat.
They probably work fine on an iron manifold.

 

I have an aluminum vintage manifold on a 327 and the chrome non steel T-Housing leaks and has corrosion issues. I was given a couple of older GM counterparts bead blasted and corrosion and hairline cracks were evident on them as well. I have proper coolant in the block now. What was in there prior I am unsure...

Is there a good quality chrome or polished Housing available?

So galvanic happens between unbarriered dissimilar metals...is die cast and aluminium in fact that?

 

The Mr. Gasket housing looks to be chrome plated aluminum or pot metal, it's not steel. I am using a 50/50 antifreeze mix. Here's the weird thing, both my cars, my '46 and my '32 have the exact set up. SBC, with Walker radiators and the same thermostat housing, yet my '32 has 55k on the odometer and the housing is in great shape. Why the housing in my '46 gets eaten is puzzling.

 

It probably only takes microscopic breaks in the surface coating to allow corrosion to set in.

Galvanic Corrosion and Corrosion are similar (or are they?) in that the end result is failure...I face sanded my Stat housing and that may be a huge no no...

 

Having solid grounds goes a long way in preventing galvanic corrosion. Shorted coolant sensors leaking voltage to ground can be a major cause of it also.

 

I think you might be on the right track Doublepumper. The reason I am leaning towards grounds is that my '32 is a glass car and I have grounds everywhere and as I said the housing is perfect. Temperature sensor is working fine.

 

Does your glass car have a Chinese thermostat housing? If it does it will leak regardless of how many grounds you have.

 

Why not a nice painted cast iron one from Rock Auto, or one of the local parts places?


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That would work Andy, but I need one that is straight up not angled.

 

Probably not the same issue, but I couldn't stop slight corrosion in my original style radiator. The local radiator bloke used a multimeter on the coolant and found a few volts present. I put a earth lead to the radiator and cured the problem. He told me it's a very common problem with aluminium radiators, especially ones from China as they don't coat the internal surface.

 

Mopar straight up stock ones are cast iron

 

@nochop does that interchange with Smallblock Chev V8? OP is SBC

 

I remember going through this a while back, and I think one of the Mopar housings is the same bolt spacing as the SBC. After having having a few chrome plated caca housings chew through, I found a NOS cast iron one, gave it a squirt of black, and it went for years.

 

I'm not terribly knowledgable on this, but you could Google "sacrificial anode", "catholic protection", "radiator cap anode", or similar. As I understand it --

A sacrificial anode requires a "closed loop" electrical path; from the anode (e.g., zinc) to the cathode through an electrolyte (coolant), and a conductive path from the cathode back to the anode (a cable, or any metal components that are in substantial electrical contact). In many cases, radiators are practically isolated by rubber mounts, hoses, etc. And the path through the electrolyte is longer than optimum. The radiator cap anode is better located to protect an aluminum radiator.

If the therm. housing is aluminum or a zinc alloy, it will be a "sacrificial anode", corroding to protect the iron heads/block. If the housing and heads are aluminum, they are anodic relative to the iron block, but the large wetted surface area results in loss of very little depth of the aluminum.

Zinc is very close to aluminum in Galvanic potential, so isn't a great anode to protect aluminum. Magnesium generally would be preferred.

Most coolants provide adequate protection, without anodes, but lose there effectiveness over time, and should be replaced periodically. I suspect the major manufacturers would have technicians available to provide recommendations on this subject.

I'm wondering if it might be worthwhile to coat the housing wetted surfaces with epoxy, and use non-metallic gaskets, stud sleeves, and washers, to isolate the housing electrically.

 

Look for 70s Chevy Van for straight up housing . I had a few but when the Chebbie left so did the part stock pile .

 

Not very "HAMBy" but this looks as good as the day it was put on 10+ years ago.

 

That is great but I'm picky about what I put on there. Mine is probably repop but has that mid 60s or older look...my question is, is there a chromed half decent 65is vintage water neck that give good service without leaking and corrosion...my ribbed hose has to go to as it has served it's time as well.

It sound as if I may have to go with painted for quality purposes.

 

So I have a Chrysler 392 that had aluminum plates over the water outlets in the heads and block. this is a marine conversion. The plates were attached with stainless bolts in the cast iron heads and block. An aluminum elbow fitting was threaded in for water hoses to attach.The anodized type you see on racers and street rods. Recently I was preparing to roll the motor to another spot and brushed one of the fittings with my hand. The fitting fell away from the plate in a crumble of aluminum chips. This alarmed me and I immediately
removed them all, 6 in total. I was relieved that the plates and fittings had all deteriorated but there was no
damage to the motor block or heads. I fabricated some new plates used steel plate and brass fittings. The brass fittings that were in place already showed no signs of
corrosion. Man I did not want to lose that 392 and was
quite relieved.

 

The main cause of galvanic or electrolytic corrosion is using the metal parts of the car for ground returns.
Run a separate ground wire to everything electrical and the problem goes away.
All of the ground wires need to return to where the battery is grounded to the frame..

 

Pete1 is correct, grounds. What hasn't been mentioned, ground the rad to the block, ground the rad to the frame as well, not with nuts and bolts, but with a 10 gauge wire, and you'll pretty much cure the problem.

 

Aluminum reacts as a sacrificial anode the same as zinc, when in the presence of iron/steel in an electrolyte. It gave its life to protect the 392.

 

I have a sacrificial anode in my radiator drain, I should replace it.. been in for 3 years. I have an aluminum radiator, heads and intake. I run a ground strap (SK Speed item..) from the radiator to the radiator support. I have more grounds elsewhere.

 

Got one on mine,can’t remember which t stat though. I think there all the same

 

Can somebody explain to me what a sacrificial anode is? Seriously, I've not heard of this.
School me...