20 replies to this topic

[tuxedoss]

Was looking at getting all the K frame and rear training arm bolts and nuts zinc plated. Then saw the plating process can make them brittle due to hydrogen embrittlement. Anyone done this and had any issues ? From what I read the harder the bolt the worse it is so is it only an issue for high tensile bolts , the k frame bolts look to be just normal bolts ,the only marking on them is a star so no rating by the looks

[torana?]

The star is the rating the more points the stronger the bolt

[tuxedoss]

The star pattern is different to what google shows but the control arm bolts and rear trailing arm bolts have 6 points making them grade 8 but the UNF caliber bolts which look to be hi tensile only have 3 points .

[grumpy xu1]

Tell your plater, they're suspension bolts, he may change the prep process a little for that reason, if they're cone nuts, don't forget, they're single use, in reality.

[tuxedoss]

Tell your plater, they're suspension bolts, he may change the prep process a little for that reason, if they're cone nuts, don't forget, they're single use, in reality.

I did and thats how the conversation started, he said they need to be baked within 24 hours of plating but he can't do it and only place he knew only does big batches and is expensive.

While the pattern on the bolt is not quite the same as I've found with google I'd say its a grade 8 bolt, surprised the caliper bolt is only grade 5

 

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[V-SLR5000-P]

Three to four hours in your home oven at 375 degrees F should see the hydrogen removed. The higher the tensile strength of a bolt the longer the baking time required. Baking must be done within an hour of plating.

[WhiteA9XS]

Been zinc plating bolts for years including suspension bolts , never had one break yet , I try and use the original old bolts if in good condition if possible .

I have heard from an engineer that the old grade 8 bolts are stronger than the new grade 8 bolts .

[dattoman]

My plater is a baker

But he's in Perth

Find a better plater... one that does aircraft stuff

[Ice]

My plater is a baker
But he's in Perth
Find a better plater... one that does aircraft stuff

Anthony

[dattoman]

Yep thats him

Moved to Maddington now though

[Ice]

Yep thats him
Moved to Maddington now though

Good to know cheers Neil

[tuxedoss]

Thanks for all the info, I have found another plater in Sydney that does baking so will give them a call and see what they say, just not sure if they do small jobs

[Ando]

Do a home destructive test on one that's been zinc plated. Use a press to test shear. A hammer to test impact.

 

I'm a bit sceptical that an electrolysis process can change the metallurgical structure of a high tensile bolt, rendering it brittle. 

 

Heating & quenching..Yes but that's another matter.  

 

Would be interesting to see the results.

[S pack]

Some light reading https://www.greensla... Appearance.pdf

[Ando]

A good read. My conclusion from that is;

 

The Torana suspension arm bolt is a grade 8 type (Rockwell C36) & it isn't used in a high tensile application. 

 

A destructive test would be in order, for ones peace of mind though.. 

[tuxedoss]

I reckon youd be unlucky for a failure but just wasn’t sure , seems a grade 8 can be 33 to 39

[Toranamat69]

At work we had a recent failure of a zinc plate high tensile bolt inside a gearbox of a train gearbox. Metallurgical analysis concluded this was hydrogen embittlement. It can happen but that is the first time ive physically seen it happen. Bolt was not in a high stress application. Highest stress was from initial tightening torque.

[grumpy xu1]

I believe it's mainly the pickling process & brightner that can cause any issue. So i would be changing the prep procedure a little.

[WhiteA9XS]

Thanks for the link Dave , just as well I didn’t toss the old oven , moral of the story don’t clean bolts with acid , I use bead blasting wash with water then dip .

[tuxedoss]

Thanks for the link Dave , just as well I didn’t toss the old oven , moral of the story don’t clean bolts with acid , I use bead blasting wash with water then dip .

Yes it seems the issue is more with the acid cleaning than the plating

[grumpy xu1]

Yes it seems the issue is more with the acid cleaning than the plating

That's what the pickling process is.