Princess Royal Mazak rot

[ColinB]

This a photo of Mazak rot for anyone that is interested. I bought this supposedly never used loco and found this. Fortunately I have now bought a replacement chassis. I only noticed as I had the usual fault motor does engage with gears properly. You will also notice the chassis is becoming like a bananna.

[DarkRedCape]

Forgive me for hijacking your thread Colin, but what is Mazak rot? And how can I identify it?

I’ve seen the term mentioned before, but didn’t know what it was.

[96RAF]

Mazak rot is caused by contamination of the mixture used to make these castings. this causes the material to expand due to corrosion which exhibits the typical distortion, crumbling and total failure of the part.

Without strict control of the basic materials used in the mix there is no way of preventing the problem and there is no way of fixing it once it starts to show.

Whether you get Mazak rot or not is in the lap of the mixing gods in some grubby back street workshop in a far-flung paradise.

[DarkRedCape]

Can it spread from part to part, or will it just be contained to the contaminated part?

[ColinB]

Well I hope I spelt it correctly, there are lots of posts about it. From what I can gather it is am imbalance in the lead mixture used in the diecast. You get a chemical reaction that make the casting brittle so it cracks and bits fall off. This is the second loco I bought that had it, the first was a Royal Scot that I bought as a non running. On mine it always seems to rot the most around the motor area although I do have some loco weights that have suffered the same. I think Hornby had sorted it on their Margate models, it appears to have resurfaced when they used the Chinese manufacturers. We know from the children's toy scandal of lead in the paint how the Chinese love their lead. I just posted the subject to help anybody identify it, usually because the loco runs badly. That loco was made by the previous management so I am not blaming the current Hornby. The only thing I wish is that they would sell off spare new chassis, so it would be easier to fix the issue.

[threelink]

It is my understanding that mazak rot is caused solely by contamination of the alloy mix. British made models of the 1950s onwards were subject to such strict quality control that the problem was pretty much unheard of. Sadly it seems that quality control in respect of more recent far-East items may be somewhat lacking, hence the recurrence of the issue. Sadly there is no known cure and affected items can only be discarded and replaced. I am not aware of such rot being in any way "transmissable".

[ColinB]

Some of the late 60's/70's Amal carburettors suffered from it, mainly from using too cheap a material. Surprisingly the earlier ones didn't. On my Royal Scot chassis, motor holder (two parts) both suffered from it, so I assume the parts were made at the same time. If you look on EBay there is a Seller selling raw chassis with it ( just look at the ends with broken off tabs). Looking at all the posts I just thought it it was limited to Royal Scot/Patriot locos as you see lots of posts about it, so you can imagine my surprise when I found it on a Princess Royal.

[Going Spare]

On the rmweb forum, there is a list of affected models from all manufacturers - search for "Zinc Pest (Mazak Rot)"

[atom3624]

There's a pretty long list that's available, as mentioned.

What is curious, is that I have several within that list, and it seems that just because your locomotive may be on that list, it may not necessarily have been affected - certain 'batches' of supplied MAZAK were and had been used within the quotas for the locomotives listed - you may be lucky as I appear to have been, and yours had the more-normal, better quality material used.

Al.

[ColinB]

Yes, that seems to be the case. I have not noticed it on any my others although I did have a weight on a West Country that suffered from it, the loco seems alright. The really worrying bit is you pay serious money for an unused one on EBay and you might get that. With both of mine that had issues it showed itself by the motor not engaging properly with the drive. Something else we have the Chinese to thank for.

[The son of Triangman]

There are quite a few Hornby locos that have had it since the China news. I believe Hornby have eradicated the issue now.

List of affected locos found on rmweb, it's by no means complete as I have come across several Hornby 9F versions with rot. The Bachmann 9F suffers from chassis rot as well.

https://www.rmweb.co.uk/community/applications/core/interface/file/attachment.php?id=1287589

A temporary fix can be done by leaving in white vinegar for a while, but it will strip the paint and the rot will still be there waiting to reappear. The only solution is the bin and a new part.