washers and aluminum...

[ford1]

over the last 30 years i have built probably over 200 ford flat head and chevy engines, and i have always used stainless steel washers and bolts to bolt aluminum manifolds to steel engines, and never once has anyone brought one back complaining about corosion , there are so many old wifes tailes and hear say out there, can any one actually prove stainless steel causes corosion? documented and with pictures?

[Jack E/NJ]

Agreed ford1. Aside from the size or mass suppression cited previously from the ENCYCLOPEDIA OF METALS AND ALLOYS, galvanic reactions between aluminum & ss usually only happen when their robust protective oxides are compromised such as by constant mechanical abrasion or by chemical dissolution in strongly acidic and/or basic salt solutions. On the other hand, non-stainless alloys that are prone to forming less robust ferric oxide (eg rust) can actually catalyze aluminum corrosion by direct chemical, as opposed to galvanic, reaction between aluminum and rust in the presence of air.

Jack E/NJ

[Binx]

Okay, Jack E/NJ, Obviously you know your stuff, but I'm going to lay this out in the most basic terms so all can understand --Rotorwrench will giggle 'cause he knows where it came from.

Avoiding dissimilar metal corrosion is a matter of keeping anodic metals away from cathodic metals. The recipe for disaster is electrical current, direct contact, and electrolyte (both liquids and gasses--even air). Engines have all three so separation is the best option.
So, I'll list the most anodic (reactive) to cathodic (least reactive) that you'll commonly find. The key is, keep these materials away from each other i.e. top ones don't mix with the bottom ones. Here we go...

Magnesium
Zinc
7075-T clad aluminum
5056 aluminum
Pure aluminum
2024 clad aluminum
Cadmium
2024 aluminum (non clad)
Steel
Iron
Lead
Chromium
Brass and Bronze
Copper
Stainless Steel
Titanium
Monel
Silver
Nickel
Iconel
Gold

I think Ian NZ has the best recipe with the hardened steel cadmium plated washers.

Lonnie

[svm99]

I'd use the hardened washers, Gardner Wescott in Michigan produces a plated hardened washer, check their website. I'm in the mfg business and I've seen some bad corrosion when SS is mixed with aluminum in damp conditions.
Paul J.

[wga]

svm99 - Garlic country - heading that way in about an hour

[fordy_nine]

Sponsored Links (Register now to hide all advertisements)

It's really not a big deal which you use in regard to corrosion - unless it is a salt water boat engine. The stainless washer is inferior because it is so much softer than steel and it has a propensity to gall, causing a poor reading when torquing the head bolts. Stainless is pretty (for street rods) and hardened steel is practical (for hot rods)......Bob L

[hardtimes]

Originally Posted by svm99

I'd use the hardened washers, Gardner Wescott in Michigan produces a plated hardened washer, check their website. I'm in the mfg business and I've seen some bad corrosion when SS is mixed with aluminum in damp conditions.
Paul J.

Paul J,
Nothing like the (STRONG) pungent smell of garlic when passing thru your area in the damp morning air ! Make a man hungry for SOS ...heavily dosed with garlic parfume every time !

As usual, terrific reading and informative thanks all.

[barryfromvictoria]

Why would you get more corrosion with stainless than with steel? Thousands of stainless bolts are used on aluminum on any navy ship or aluminum boat that i have worked on. Good 316 stainless will not conduct electricity. What is a no no in a shipyard is brass touching aluminum and you will get an electrolysis. Anti seize is recomended on all stainless bolts to prevent galling not corrosion. Anti seize is used sometimes on steel to prevent corrosion not galling. What kind of bolts do you think you would use in a saltwater enviroment? I have never seen an aluminum bolt used, except for unique situations and they are usually specially made. Go ahead and use stainless hardened washers if you want. Your steel headbolts can corrode to the aluminum. I have never seen stainless washers corrode to aluminumin on an engine .---- Barry

[JM 35 Sedan]

I will never understand the logic of folks trying to justify doing something that's basically wrong to begin with. The original poster wanted to know if he could use SS washers from his local hardware store between stud nuts and aluminum heads. The correct answer to that question is he 'SHOULD' use the correct thickness hardened steel washers as were designed for and used by Ford on their assembly lines here in the US. (who knows what was done in Ford plants outside the US??). The typical SS washers found in your local hardware store are 'MOST LIKELY' too thin and too soft to work correctly....and besides not being mechanically correct some manufacturers/suppliers of SS hardware recommend not using their products in/around/on aluminum because of known problems that have occurred in curtain applications. Now....having said this...my recommendation for those who would prefer to use SS washers between their stud nuts and aluminum heads....DO IT. No one is stopping you from making that mistake, IMO. For those who would rather use the correct type washer in that application....DO THAT. There are many sources that offer the correct washers in the correct material, thickness and hardness. We all have choices on what we do. Some make the right choice and some don't. It's your call,....N E X T!