Galvanizing process

[jake1]

Sept.29/05
A question to all forum members: I have read that galvanizing steel protects it from rusting. Most chassis are coated or painted. Is there any reason that galvanizing is not used for this purpose in GT40's?

[Andy]

Hi Jake,

Some mnufacturers do use galv processes.
Goran's steel to make the chassis are first hot galvanised, then after welding are treated again, with the same process as Volvo's chassis. Its then recommended, that all internal chambers in the monocoque are injected with a rust preventative.

[Phil]

Jake
I have experience in this area so here goes....
I can tell you that galvanizing does protect the steel underneath from corrosion. The only thing to interrupt this protection would be some type of mechanical abrasion stripping the coating, once one spot is bare rust tends to travel depending on the position and location of the blemish. Also it is important to have the galvanizing done by a reputable shop, there are several steps in the process such as acid dip, flux dip, etc. to inprove adhesion. The only drawbacks To galvanizing are that is is difficult to make paint stick, and areas such as tubular sections of the chassis need to be vented before being dipped. This is because the hot zinc is at about 850 deg.F or hotter, and there is a chance that closed tube sections of a chassis for example can actually blow out. I tried once to have a set of railings galvanized and sent them without any venting holes...well they came back galvanized but with ugly holes in the horizontal and vertical components cut by a torch, so if you are doing a chassis it has to be vented if it has any closed sections. Otherwise it is great protection if you don't mind the color
Regards
Phil

[roy snook]

Charley,
The steel you are talking about from which Goran and I made the first monocoque tub is zintec. I purchased it in the U.K and machined the panel sets here at my premises on one of my CNC machines. The panels were then shipped to sweden where we assembled the 'Prototype'I will post pictures of the machined parts for you guys to see.

[J What?]

Galvanizing is a terrible process to work with. It is hot dipped which gives it a lumpy finish as well as hard to paint etc. It is just thick zinc so I think, if you really wanted to do it, have it electro plated with zinc. You will still have the paint sticking problem but maybe the zinc color is what you are looking for.Personally I just don't like dipping tubing in any solution. The inside does not get coated, even if you drill holes, due to lack of circulation as well as air bubbles. Most of the solutions start the rust process prematurely if the steel is not plated well. If the chassis is welded well there is really no reason to coat the inside of the tube. I think powder coating the chassis is a much better solution and just as tough and it looks much better.
Bill

[David Morton]

Jack,
It eventually goes a much darker grey and any subsequent work that disturbs the coating will be a corrosion point.
Much easier to use a good paint process - the type that is used on trucks over a primer then baked is especially good and takes loads of knocks without chipping. It's a wet spray - not a powder coat. Any areas where subsequent work is done can be painted again and left to air dry. And yes, there are some company's around that can get a whole chassis into an oven.

[Andy]

David,
Surely whether it be a monocoque or a spaceframe, the inside sections will not be coated and thus will begin rusting from day one.Perhaps you could inject these hollow sections with some type of rust inhibitor/oil etc. What im concerned about, is the chassis will still look great from the outside, until the day the inside rust 'makes a break for freedom', lol.
Please correct me if i have overlooked something.

[David Morton]

Absolutely, and I guess that's why many original cars had to be rewelded onto jigs and the old rust moth sorted out.
I don't think the cars that did Le Mans had much paint on them at all. I saw a few of the Saphir cars being built by Henry Atherton in High Wycombe. He was using Zintac which Roy alluded to earlier but as far as I know, they got painted afterwards. I cannot verify what they did on panels or compartments where paint couldn't reach. I suppose we, on our cars, could spray Dinitrol or Waxoyl if it really was bothering us. On my GTD everything was painted where ever it could be, some urethane 2 part foam was used to prevent ingress of damp, and the rest was inaccessible anyway. But it never goes out to get wet anyway. [img]/ubbthreads/images/graemlins/crazy.gif[/img] [img]/ubbthreads/images/graemlins/smile.gif[/img]
DM

[Mike-M]

Hi jake,

hot dipped galvanising is a high temperature process in which the steel has to be raised to the molten temperature of the galvanising bath in order to achieve proper zinc adhesion. during this process the welds and parent metal of the fabrication tend to be stress relieved and softened, if not supported adequately by cross bracing the chassis will warp/distort to unacceptable degrees in all 3 planes.

hope this helps

regards
mike

[Trevor Jones]

Some years ago I decided to base my monocoque chassis on galvanized sheet. Since spot welding can be made compatible with galvanizing, the trick was to design the chassis to maximize the use of spot welds and work out an order of assembly so that there were a minimum of blind welds.

Takes quite a bitof thought to work out the correct order.

Anyway the chassis is now nearly 10 years old and not a spot of rust on it; but then again it rarely goes out in the rain.

Have attached some photos. They are digital pics of the original 'analog' photos so quality is degraded.

[Trevor Jones]

Here is one of the under side

[Trevor Jones]

... and a rear view showing the rear subframe

[goran]

Re Hot galvanized steel! I´m using the same material as Volvo, Saab, Mercedes and most of the other. It is a high strength material for deep drawing that is hotgalvnized during the process. The tensile strength is 380N/mm and very good to deep drawing since we press almost every panel to get the accuracy. The first one´s was milled by Roy but I nowdays lasercut all parts to get top quality since there it can be a problem with movement when milling and then the tolerancechain moves. I will post 2 pic so you can see that the weldability is 100% and the Zintex that we used in the beginning is not the material to use in my oppinion when there are better material to use. I have discussed the choise of material with several guys that have long experience in the area and I fell that I have choosen right. I´m using 6 very heavy watercooled industrial spotwelders with high force between the jaws every each individaual equipped with differnt javs to be able to get in the chassie and make quality weld. I´m posting some pic so you guys can see. We are running the project from Sweden and if anyone is interested and want to know more they can contact me directly. About corrosion this material is outstanding compared to Zintec. To hotgalvanise a complete monocoque would result a trip to the scrapyard. I did that on some spaceframe chassies in beginning of the 90´s and it was one hell of an job to get them straight in a bench. The monocoque would look live a winescrew. We have built 80 more tools and a closing production really fast.

Best reg!

Goran

[goran]

Another pic!

[roy snook]

Here is a picture of some of the flat panels after machining. I have left cut Zintec steel sheet outside for over a year and the ingress of corrosion on the edges is negligable. The material can be dipped after machining to protect against corrosion until the final surface (colour) is applied. It is true you do need to be very careful when machining to ensure accuracy of the finished panels but this is not difficult to achieve. .

[Trevor Jones]

here are a couple more pics of the chassis

[Trevor Jones]

...and this one