Which Bolts to use

[dickyjoe]

Hi All,

I am planning a reburb of my 1984 110 Land Rover "Mongol", some of you may have seen it in the Nth East section of the forum.

Anyway I am looking at Galvanising the chassis and the firewall using the local company's who are rebuilding the army Land Rovers.

The question I have is what is a good type of bolt with a coating that I can use to use on the rebuild. What would work best with contact with galnanised steel and aluminium. I am rebuilding this truck to last me so I don't want to be looking again at it in 5 years time.

My thoughts were ZINC coated bolts or even the cadmium plated bolts. I don't know enough about metals though.

Please Help!

Rich

[Blknight.aus]

Id be looking at cad plating or a nickle based antisieze compound.

[JDNSW]

Landrover decided this sixty years ago - galvanised (not zinc plated) bolts.

John

[dickyjoe]

Hi Blacknight / John

Thanks for your input.

Which bolts are galvanised John?

I have had a look at cadmium plating kits online. Has anyone had any success with one of these?

Rich

[isuzurover]

The bottom line is that the galvanised chassis will protect any bolts in contact with them from corrosion. I would be happy with zinc plated bolts - class 8.8 +

[JDNSW]

Galvanised bolts suitable for all body bolts should be available in metric sizes, albeit you might have to get them ordered in and take a whole box. If in contact with a galvanised chassis, the galvanising on the chassis will protect the bolt in the immediate vicinity of the galvanising, but not, for example, the head or nut on the other side of the aluminium. Zinc plating will only protect for a short time in an adverse environment.

You should also use galvanised washers, although you will probably have to settle for zinc plated spring washers.

The original bolts used in Series 1 bodies were Sherardised, coated with zinc by a process of vapour galvanising. This has the advantage that the zinc is diffused into the steel, making them more durable and not significantly changing the dimensions (hot dip galvanising requires the thread to be cut deeper before galvanising, and often needs a die run over the finished bolt). However, it is a relatively labour intensive and hence expensive process, and as far as i am aware is no longer done on a commercial scale.

John

[dickyjoe]

Thanks all for your help. This is going to make my truck last longer, which as I see it is a good thing!

[dickyjoe]

So put simply would Gal be much better than Zinc bolts.

It seems its much easier to get Zinc bolts over Gal. Would the Zinc bolts chew out the alloy or something?

Rich

[one_iota]

Rich,

Galvanizing applies the Zinc to the steel in a molten form where as Zinc plating applies the zinc electrolytically:

Galvanised Coatings - Zinc Galvanising versus Zinc Plating (http://www.azom.com/details.asp?ArticleID=1380)

So there will be no difference corrosion wise.

The benefit of galvanising is that the Zinc coating can be thicker and therefore can last longer. However as JD says, on a bolt this is problematic as the coating will "clog" the thread.

Zinc is close to Aluminium in the Galvanic Table and is probably and practically the best coating for a steel bolt going through an aluminium panel. However if you can seperate the materials with say rubber or paint all the better.

Happy to be corrected on this though.

In fact they now coat steel roof sheeting with a Zinc/Aluminium coating for corrosion protection.

[JDNSW]

Rich,

Galvanizing applies the Zinc to the steel in a molten form where as Zinc plating applies the zinc electrolytically:

Galvanised Coatings - Zinc Galvanising versus Zinc Plating (http://www.azom.com/details.asp?ArticleID=1380)

So there will be no difference corrosion wise.

The benefit of galvanising is that the Zinc coating can be thicker and therefore can last longer. However as JD says, on a bolt this is problematic as the coating will "clog" the thread.

Zinc is close to Aluminium in the Galvanic Table and is probably and practically the best coating for a steel bolt going through an aluminium panel. However if you can seperate the materials with say rubber or paint all the better.

Happy to be corrected on this though.

In fact they now coat steel roof sheeting with a Zinc/Aluminium coating for corrosion protection.


The difference in electrochemical potential of aluminium and zinc is still considerable, but it is less than steel and aluminium, and the fact that both zinc and aluminium form a hard insoluble layer of oxide is an advantage. But particularly if there is any possibility of movement on the joint, some form of insulation, at the very least paint, is preferred, since the aluminium will be preferentially attacked..

In galvalume, where sheet steel is coated with a mixture of zinc and aluminium, the function of the aluminium is to provide a much harder and hence more durable oxide surface, as aluminium oxide is more impermeable and harder than zinc oxide.

John

[VladTepes]

The bottom line is that the galvanised chassis will protect any bolts in contact with them from corrosion. I would be happy with zinc plated bolts - class 8.8 +

:confused: How? By magic ? By setting a good example ?

Surely the fact the chassis is galvanised will limit/prevent corrosion *at the point of contact between bolt and chassis* but it's not going to protect a bolt from anything else - like rust from salt water etc.

[dickyjoe]

And so....

If you were doing up a Land Rover with or without a gal chassis and you had to purchase the bolts would you use Zinc or Gal? The local bolt man doesnt seem to have Gal but has Zinc and I was wondering if its going to make it that much better or maybe the difference would be negligable.

Rich

[isuzurover]

:confused: How? By magic ? By setting a good example ?

Surely the fact the chassis is galvanised will limit/prevent corrosion *at the point of contact between bolt and chassis* but it's not going to protect a bolt from anything else - like rust from salt water etc.

Zinc corrodes preferentially. Any bare steel in contact with zinc will be protected for ~+/- 5mm either side of the contact, and further away will only develop light surface rust usually.

Steel boats have a few lumps of zinc screwed on their hull to prevent corrosion (but that is immersed in electrolyte).

The IIA dad and I built for him has all the steel body bits galvanised, but mostly standard bolts. It has been on beach /fraser etc fishing trips many times over the years. The bolts are fine.

[slug_burner]

If you can get them use cad plated hardware otherwise use paint to protect the surfaces.

Paint is cheaper and easily applied.

Lanolin/lanotech is another surface application which appears to have come into vogue more recently and appears to have got acceptance from many as it is natural and less harmful than the metal plating heavy metals and chemical used in the process of preparing or used as a medium to hold the metal in some solution in order to apply it.

[Davo]

I just use Grade 5 UNF zinc-plated bolts that you buy in boxes of 50 or 100. I've found over the years that when you go to enormous lengths to rebuild your Landie to be perfect, there's always something that doesn't quite go the way you planned and so it's never quite that perfect after all. And then other things come up and you don't care so much. So now I use what good quality stuff I can get and othewise don't worry about it.

[Dougal]

Galvanised bolts are typically available in only softer grades like 4.6.
You have to go for zinc electroplate or cadmium plating in harder grades.

[JDNSW]

If I could get them I would use galvanised bolts in preference to zinc plated. The problem is that the plating is usually (not always) so thin that it is broken by casual impact, such as using a spanner or the nut running along the thread, so that it is easily attacked.

It is about four years since I did a body off repaint on my 2a. Where possible I used the original galvanised bolts, but had to replace some of them with zinc plated ones (could not get galvanised UNF bolts and did not want to use metric). The forty year old galvanised ones are mostly still OK. The four year old zinc plated ones are all rusty.

I cannot think of any of the body bolts where the grade of bolt matters, as none of them carry a lot of load - possibly the ones mounting the bottom of the firewall, but that is about it.

John

[isuzurover]

I cannot think of any of the body bolts where the grade of bolt matters, as none of them carry a lot of load - possibly the ones mounting the bottom of the firewall, but that is about it.

John

All the body bolts are Grade 5 - which is ~ Class 8.8 in metric. Although that may be overkill, I wouldn't want to decrease the strength of the bolts. Most of them may be overkill, but a lot of them are small, and prone to snapping during removal.

[roverrescue]

"Structural" grade bolts are Class 8.8 hot dip galvanized

BUT

you may struggle getting them in the smaller sizes required and they will be the new fangled metric threads!!!

Galvanic Table (snipped)
Active (Anodic)

1. Magnesium
2. Mg alloy AZ-31B
3. Mg alloy HK-31A
4. Zinc (hot-dip, die cast, or plated)
5. Beryllium (hot pressed)
6. Al 7072 clad on 7075
7. Al 2014-T3
8. Al 1160-H14
9. Al 7079-T6
10. Cadmium (plated)

Clearly the best fasteners for the job at hand would be forged from Beryllium!!!!!! The list certainly makes Cad plated look the most logical choice being only just more cathodic than both the gal chassis and Al panels commonly available and easy to source in the correct sizes and grade. Zn plated bolts surface scratch to easily and generally hot dip Zn bolts (apart from structural) are generally low grade with poor tolerances.

Steve

[Dougal]

"Structural" grade bolts are Class 8.8 hot dip galvanized

They're certainly galvanised, but is it hot-dip or some better method? The finish on HSFG bolts appears better than your average grade 4.6 hot dip galvanised bolt.

[roverrescue]

yeah good point Dougal.
Im unsure of the process but the structural grade bolts I source have a very thick Zn coating (test with grinder) yet have near perfect tolerances in shank diameter and thread pitch / size. I would use them exclusively but can really only sorce them in the usual "structural" sizes, longer shanked M10, M12, M16, M20 then upwards.

Steve

[mark2]

When I galvanised and rebuilt my 110 and (2 x2A's) , I used most of the original bolts but put nickel based anti sieze (looks like silver grease) religiously on just about every thread that didnt require loctite. Even if the original bolts are a little rusty, a wire brushing and the anti-sieze is all they need.