Basic Metalurgy

[thatch]

67c&ccorv,
Thank's for your responce. You are perfectly correct in saying that we should always be careful to use the correct length fasteners. I have run accross cases (on other types of engines) where you could actually crack a cylinder wall by using a bolt that was too long.
The word "Bodger" was new to me and since I was unable to find it in my dictionary I decided to do an internet search on it. The best I could come up with was that it was a name given to "highly skilled itinerant wood workers in a small town between Oxford and London", so I guess I will take it as a compliment.... Now, Botcher, that's another story completely.
Regards, Tom

[67c&ccorv]

Claims by Universal of "high nickel-chromium" notwithstanding, the empirical evidence clearly shows that these engines are highly subject to corrosion in the marine environment, both galvanic and otherwise. The engine castings are indeed mostly ferrous - containing alloys of nickel and chromium, but not enough to move them up significantly on the galvanic series so that they might be electrochemically immune from attack by more noble metals!

Approximately 70% of the material used in the composition of stainless steel is ferrous iron - even 316 stainless. (And yes, stainless steel is subject to corrosion depending upon the environment it is situated in - especially low oxygen environments.)

Unless you want to cast in in bronze or titanium (or unobtanium) there is no steel that will not eventually corrode - it is just a matter of how fast and how long.

Whatever the composition of the castings Universal used/was(?) I would suggest it goes a long way to explaining why nearly one half of the 20,000+ engines built are still operating.

Some, (as in my case) still with the original block and castings from the 1960's and earlier.

[ndutton]

Approximately 70% of the material used in the composition of stainless steel is ferrous iron - even 316 stainless. (And yes, stainless steel is subject to corrosion depending upon the environment it is situated in - especially low oxygen environments.)

Do I interpret this to mean we can expect dissimilar metals issues between stainless and iron to be minor, or easily mitigated with something like anti-seize?

[hanleyclifford]

dissimilar metals

Do I interpret this to mean we can expect dissimilar metals issues between stainless and iron to be minor, or easily mitigated with something like anti-seize?

It is well established in the (especially) wooden boat building and repair business that issues of dissimilar metals are NOT minor and galvanic corrosion can be startlingly rapid in some instances. Look at the wood and note the stringy yellow fibres near the offending cell, as well as the white or blue powder near the cathode. What determines the intensity of the cell is the degree of dissimilarity of the metals. This is why we always consult the galvanic series chart before using two metals in proximity. The stringy yellow fibres are the result of what is called electromagnetic delignification at the cathode. Of course in metal the destruction is the result of the noble metal stealing electrons from the less noble. In the case of an engine block just about anything is going to be "more noble" except for the useless stuff like aluminum etc. Tom uses capscews plated with cadmium; the cadmium is anodic in this case and should in fact to some extent "take the galvanic hit". Stainless steel at a location like, say, the oil pan would be deadly because it would tend to steal electrons from the casting even an alloyed one, albeit at a lesser rate than one of straight "pot" iron. As far as the use of antiseize products is concerned, I don't use them. Read the label and see what a mini self contained little galvanic battery it has the potential to be.

[FelicityRebuild]

ok. I love that my first two questions I ask this panel have sparked (almost) heated debate. Between this discussion and the question I posed about the valve guides, It's been very educational. I was warned that I may get 50 people giving me 100 different answers. I can handle that. I've learned in my life to listen to all perspectives then make my own decision. I appreciate all of your help and I thrive on scientific discussions such as these. However. I'm still at a loss as to what type of metals to use for replacement bolts. Does MMI have a standard type they use? Do they discern between an oil pan bolt or a bolt that goes on the transmission cover, or do they use the same type for all? Maybe there is no answer. I do realize that that's a possibility. If that's the case, I'll simply make a note of the bolts I replace and keep a very close eye on them. I'm ok with that option too.

[ndutton]

. . . . . that issues of dissimilar metals are NOT minor and galvanic corrosion can be startlingly rapid in some instances.

Yet the Moyer Marine water jacket side plate bolt repair kit is all stainless!

ref: (CSOT_04_307)

[hanleyclifford]

nuts and bolts

You will never go wrong using the grade 5 medium carbon steel, with the cadmium plating (like Thatch) if you want a little anodic protection. Many special fasteners are listed in the online MM catalogue. The grade 8 is nice too if you can spring a little extra $. Definitely check the catalogue first.

[hanleyclifford]

Yet the Moyer Marine water jacket side plate bolt repair kit is all stainless!

ref: (CSOT_04_307)

Another strong argument to have a top quality antifreeze cooling system!

[hanleyclifford]

One more point on the MM repair kit. This item actually replaces the original threads in the casting with a "thru bolted" unit. It is threads that are most vulnerable to galvanic "assault". Once installed the repair kit sets up along its entire length against the casting thus spreading the connection against a much more substantial metal surface. In an antifreeze environment, other things being normal, I might start looking for trouble from this installation after around 50 years.

[thatch]

It's all your fault, Felicity!

In order to keep this thread spinning out of control I'll throw another little thought into the mix. During my current A4 rebuild on my spare motor and on other engines where strength is not an issue I use brass. In the case of the A4, the brass will be studs locktighted (red) into the block and I will use brass washers and nuts to hold the parts in place. The 3 particular parts that will get this treatment are the transmission cover, the block side cover(water) and the 2 carburator mounting studs. Brass seems to about the least offensive of the non corrosive type of metals, and dosen't gall. The use of studs does a couple of things that I like, they save wear and tear on the threads in the block or manifold and and I find it easier to line up the parts for reassembly. Red locktite holds better in these cases like these and a little heat will loosten them up if you have to remove them. Any thoughts?
Tom

[hanleyclifford]

keep stirring

In order to keep this thread spinning out of control I'll throw another little thought into the mix. During my current A4 rebuild on my spare motor and on other engines where strength is not an issue I use brass. In the case of the A4, the brass will be studs locktighted (red) into the block and I will use brass washers and nuts to hold the parts in place. The 3 particular parts that will get this treatment are the transmission cover, the block side cover(water) and the 2 carburator mounting studs. Brass seems to about the least offensive of the non corrosive type of metals, and dosen't gall. The use of studs does a couple of things that I like, they save wear and tear on the threads in the block or manifold and and I find it easier to line up the parts for reassembly. Red locktite holds better in these cases like these and a little heat will loosten them up if you have to remove them. Any thoughts?
Tom

Tom, You did not specify which type of "brass" - various types are all over the galvanic series chart. Regards, Hanley

[thatch]

My arms are getting tired!

hanleyclifford,
In my copy of "Thomas J. Glover's Pocket Reference" book the brasses (Cu+Zn) fall in about the middle of the page, with Platinum being at the top and Magnesium and Magnesium alloys being at the bottom. If I were to ask the fellow at my local metal supply house what "kind of brass" all-thread he carried, I'm pretty sure he would just stare at me or use some foul words while telling me to leave. In short, I don't know, but since I have yet to see an "over the counter" brass nut or bolt that has caused a problem then I won't worry about it's content.
Tom
P.S. At about $11.00 I highly recommend "Glover's Pocket Ref." book; it is absolutely facinating!

[67c&ccorv]

In order to keep this thread spinning out of control I'll throw another little thought into the mix. During my current A4 rebuild on my spare motor and on other engines where strength is not an issue I use brass. In the case of the A4, the brass will be studs locktighted (red) into the block and I will use brass washers and nuts to hold the parts in place. The 3 particular parts that will get this treatment are the transmission cover, the block side cover(water) and the 2 carburator mounting studs. Brass seems to about the least offensive of the non corrosive type of metals, and dosen't gall. The use of studs does a couple of things that I like, they save wear and tear on the threads in the block or manifold and and I find it easier to line up the parts for reassembly. Red locktite holds better in these cases like these and a little heat will loosten them up if you have to remove them. Any thoughts?
Tom

There is some pretty crumbly brass out there - why not bronze (which, to add to the confusion comes in a number of different compositions).

[hanleyclifford]

67c&ccorv - Good question. Bronze is much more durable than brass and generally stronger in tension. But before we forget, the issue of the galvanic cell does not arise unless an electrolyte is present. The use of brass on a transmission cover is no problem, nor bronze; on one of my engines I have bronze "wingbolts" for quick access (and a touch of vanity). Same with the carb studs; in fact I would prefer bronze over brass in this location. The mixing of dissimilar metals in the A4 is well established. Consider the oil pump - cast iron, pickup screen - some sort of bronze, the screen frame - aluminum or some sort of "white metal". Now Tom's plan to use brass in the water jacket is a little disturbing because the brass will steal electrons from the casting if an electrolyte is present, not at the ferocious rate of bronze or stainless, but enough to be noticeable to the threads. Why not go with the cadmium plated stuff here too? I'm sure our new colleague, Felicity rebuild must think we are totally wrapped around the axle on details. So be it: I like to think of it as collective advancement of the technology.

[FelicityRebuild]

On the contrary

While I do think we're overthinking the problem a bit, I'm loving the controversy I've sparked. I do appreciate all the opinions. I'll probably go with the cad 5 provided I can find it easily and with minimal expense. I need top keep reminding myself that this isn't the warp drive on a starship. I'm just trying to turn my propeller for another 10 years.