42 replies to this topic

[MatsNorway]

There is so many ways to give steel a protective layer.

The obvious galvanizing with zink, then there is nickel, copper, silver, crome and gold if your fancy.

then you have heat threatment with zink bath.

crome zink something. with multiple names. yellow cromatising etc. (translation from norwegian dunno about english wording)

So does anyone got any experiences to chare or a good page with info on the different threatments?

[Engineguy]

This stuff is amazing... other companies market similar, but this is the brand I can vouch for from experience... I used the spray cans...
ZRC Cold Galvanizing Compound

[Kelpiecross]

There is so many ways to give steel a protective layer.

The obvious galvanizing with zink, then there is nickel, copper, silver, crome and gold if your fancy.

then you have heat threatment with zink bath.

crome zink something. with multiple names. yellow cromatising etc. (translation from norwegian dunno about english wording)

So does anyone got any experiences to chare or a good page with info on the different threatments?

What is that "yellow cromatising"? - it seems to be on most new car parts these days - especially brackets etc.

[Greg Locock]

What is that "yellow cromatising"? - it seems to be on most new car parts these days - especially brackets etc.

Chromate 6. It's being phased out, I don't think we can specify it any more, as the process chemicals are pretty toxic.

[Engineguy]

What is that "yellow cromatising"? - it seems to be on most new car parts these days - especially brackets etc.

If you're talking about steel parts:
Zinc Dichromate, Gold Iridite, Cronak, ISO 4520, ASTM B633, etc. ...
It's a long used process of zinc (or cad, I think) plating followed by a chromate conversion. The solutions (example sodium dichromate and sulfuric acid) used for the conversion dip (a few seconds) were often propriatary and hence have had trade names (i.e. Gold Iridite) causing a lot of confusion. The conversion makes the plating more durable and prevents chalky surface corrosion of the plating. The color can range from clear to clear/blue to yellow/gold to olive to black... the darker colors are most durable... yellow/gold is mid-scale in durability and, I would assume, cost.

A Gold Iridite restoration plating source

[MatsNorway]

If you're talking about steel parts:
Zinc Dichromate, Gold Iridite, Cronak, ISO 4520, ASTM B633, etc. ...
It's a long used process of zinc (or cad, I think) plating followed by a chromate conversion. The solutions (example sodium dichromate and sulfuric acid) used for the conversion dip (a few seconds) were often propriatary and hence have had trade names (i.e. Gold Iridite) causing a lot of confusion. The conversion makes the plating more durable and prevents chalky surface corrosion of the plating. The color can range from clear to clear/blue to yellow/gold to olive to black... the darker colors are most durable... yellow/gold is mid-scale in durability and, I would assume, cost.

A Gold Iridite restoration plating source

How does these threatments compare to galvanizing with nickel?

I understand now that the threatment you talk about is electroplating, correct?

Edited by MatsNorway, 05 January 2012 - 09:32.

[Kelpiecross]

If you're talking about steel parts:
Zinc Dichromate, Gold Iridite, Cronak, ISO 4520, ASTM B633, etc. ...
It's a long used process of zinc (or cad, I think) plating followed by a chromate conversion. The solutions (example sodium dichromate and sulfuric acid) used for the conversion dip (a few seconds) were often propriatary and hence have had trade names (i.e. Gold Iridite) causing a lot of confusion. The conversion makes the plating more durable and prevents chalky surface corrosion of the plating. The color can range from clear to clear/blue to yellow/gold to olive to black... the darker colors are most durable... yellow/gold is mid-scale in durability and, I would assume, cost.

A Gold Iridite restoration plating source

Thank you (and GL) for that - I have wondered for years what the coating was. The process may be dangerously poisonous but the parts certainly look good.

[Greg Locock]

Thank you (and GL) for that - I have wondered for years what the coating was. The process may be dangerously poisonous but the parts certainly look good.

Bah, kids today. One of my jobs as an apprentice was to take a sample from the cyanide bath to the lab for analysis. The cyanide bath was molten sodium cyanide, at something over red heat. That was the second most terrifying thing there. The most terrifying was Stan, the supervisor of the lab.

[MatsNorway]

Here is a great link i found about the subject.
http://429mustangcou...new_page_26.htm

Edited by MatsNorway, 05 January 2012 - 11:38.

[Kelpiecross]

Bah, kids today. One of my jobs as an apprentice was to take a sample from the cyanide bath to the lab for analysis. The cyanide bath was molten sodium cyanide, at something over red heat. That was the second most terrifying thing there. The most terrifying was Stan, the supervisor of the lab.

Jesus H. Tapdancing Christ! Better you than me.

[Engineguy]

How does these threatments compare to galvanizing with nickel?

I understand now that the threatment you talk about is electroplating, correct?

My first reply was about cold galvanizing: Like the ZRC product I mentioned... applied like paint, but it's 95% zinc. No current. Chalky if no overcoat.

My second reply about zinc dichromate: the first step is electroplating with zinc... the second step is just a dip in a chemical solution with no current. Thin and smooth coat.

The other common method is Hot Dip Galvanizing: Dipping the steel parts in molten zinc. No current. Thick, rough coating... example chain link fence.

==============
Zinc vs. nickel:
Generally zinc is better for corrosion with its ability to self-heal scratches... Nickel is fine for corrosion if not subject to scratching.
Read this...

[Lee Nicolle]

This stuff is amazing... other companies market similar, but this is the brand I can vouch for from experience... I used the spray cans...
ZRC Cold Galvanizing Compound

I have used various cold galv brush ons and spray ons. Most have been very good. Only used thenm to touch up weld areas on verandahs and the like though a mate undercoated his car trailer with it. Good but still chips like paint though and was quite dear too.

[Lee Nicolle]

Bah, kids today. One of my jobs as an apprentice was to take a sample from the cyanide bath to the lab for analysis. The cyanide bath was molten sodium cyanide, at something over red heat. That was the second most terrifying thing there. The most terrifying was Stan, the supervisor of the lab.

I have had spun steel composite rim halfs and engine bits[sumps, rocker covers etc] either silver or gold color plated over the years. It all discolors ofcourse and I have even had acouple of rims think about going rusty but generally pretty good
An aquaintance used to work in one of those places until he got very severe burns[heat and chemical] from a splash. He is now a parking inspector!!

My elderly neighbour worked in a chrome plating factory, in later life his lungs were very bad though he was still working, slowly, at 80 painting his house, fitting gutters etc

[Wolf]

I don't know why, but ever since seeing the title of this threada phrase of 'vapor deposition' keeps appearing in my mind. Might have something to do with creating ceramic coatings on metallic parts used in engines... But then again, I'd hardly be surprised if I got something mixed up and was talking complete bollocks.

[Kelpiecross]

My elderly neighbour worked in a chrome plating factory, in later life his lungs were very bad though he was still working, slowly, at 80 painting his house, fitting gutters etc

Some of these electroplating solutions are of compounds containing cyanates etc. - which are bad enough - but a bath of molten NaCN would seem to be just ridiculously dangerous.

[MatsNorway]

Whe have decided to drop Zinc Dichromate for our bolts and go for the zinc phosfate coating. IF we get it. first batch will be 200 bolts. i believe.

[Kelpiecross]

Whe have decided to drop Zinc Dichromate for our bolts and go for the zinc phosfate coating. IF we get it. first batch will be 200 bolts. i believe.

I used to work on a zinc phosphating bath (trying to make it behave itself) - it was used as a coating to hold a lubricant for drawing rods into wire. From what I saw it gave little or no protection against rusting - why would it be used on bolts?

[Greg Locock]

Some of these electroplating solutions are of compounds containing cyanates etc. - which are bad enough - but a bath of molten NaCN would seem to be just ridiculously dangerous.

It was used for case hardening gear teeth. The high temperature is necessary with any case hardening system as you are trying to diffuse different molecules through the molecular structure of the steel. That's why parts grow when case hardened.

At home my dad used to carburize small parts for steam engines by heating them to red heat and burying them in bone ash.

One problem with case hardening is that the diffusion is faster down the grain boundaries, so it gives a slightly rough texture, so you end up lapping or polishing the finished article typically.

[Lee Nicolle]

It was used for case hardening gear teeth. The high temperature is necessary with any case hardening system as you are trying to diffuse different molecules through the molecular structure of the steel. That's why parts grow when case hardened.

At home my dad used to carburize small parts for steam engines by heating them to red heat and burying them in bone ash.

One problem with case hardening is that the diffusion is faster down the grain boundaries, so it gives a slightly rough texture, so you end up lapping or polishing the finished article typically.

Sump oil seems to work too

And some of the heat treat places should realise that hardening makes things grow. I have had axles like that,, and bought timing gear sets that will not go over the crank snout. That is regularly

Edited by Lee Nicolle, 07 January 2012 - 23:26.

[MatsNorway]

I used to work on a zinc phosphating bath (trying to make it behave itself) - it was used as a coating to hold a lubricant for drawing rods into wire. From what I saw it gave little or no protection against rusting - why would it be used on bolts?

Because its supposed to give better protection thant Zinc Dichromate. It might not be much but if its a improvement it is good enough. I suggest you recommend a alternative. isnt it Zink phospathing on the 12.9 black unbrako bolts?. and they tend to last for some time.

the coating is for 43CrMo4 bolts and quenc? tempered C45 something steel.

Edited by MatsNorway, 08 January 2012 - 00:36.

[Kelpiecross]

Because its supposed to give better protection thant Zinc Dichromate. It might not be much but if its a improvement it is good enough. I suggest you recommend a alternative. isnt it Zink phospathing on the 12.9 black unbrako bolts?. and they tend to last for some time.

the coating is for 43CrMo4 bolts and quenc? tempered C45 something steel.

Sorry Mats - I have to admit that I don't know a lot about the subject. I have been surprised to see ads in car magazines offering parts that ahve been "Parkerized" - which I think is zinc phosphating (Parker being one of the suppliers of the phospating solutions). Phosphated parts look good with a matt black finish - but as I said before - I don't think it offers much protection against corrosion.

[Wolf]

Now, I may be talking out of my a$$, but (back in the days of yore, i.e. decades ago, when I was fresh at Uni, and was a 'demos' working with galvanization*), it seems to have stuck to my mind that zinc based coatings (yellowish hue) were not so much aimed at corrosion resistance, but raher related to tribological properties when mated to untreated surfaces... Sort of preffered coating for bolts because it ?increased? friction between the threads (leading to slightly, if not 'marginally', improved load capacity of bolted joint), and slightly reduced wear...

* magnitude of operation was ISTR half a pint beakers, wages of fear were measured in dollars a month, and only real benefits were slightly easier way of laying one's hands on relevant literature

[cheapracer]

We have awesome red primer paint at work they slap on to all the job pieces straight over any surface rust or oils, I'll try to find out what it is.

Hammertite was always good stuff - http://en.wikipedia.org/wiki/Hammerite

[MatsNorway]

We have awesome red primer paint at work they slap on to all the job pieces straight over any surface rust or oils, I'll try to find out what it is.

Hammertite was always good stuff - http://en.wikipedia.org/wiki/Hammerite

im fairly sure paint will not be better than a zinc coating. these bolts are a part of a joint. So there is movement going on , on some of the surfaces.

[Kelpiecross]

im fairly sure paint will not be better than a zinc coating. these bolts are a part of a joint. So there is movement going on , on some of the surfaces.

The typical middle-of-the-range high tensile nuts and bolts I buy thesedays has nice shiny smooth metallic plating of some kind (a few years ago they were just bare steel). They don't rust. I don't know what the plating is but it would probably suit your purposes.
The really high tensile bolts are black in colour - but I assumed that this was something to do with the heat treatment.

[MatsNorway]

The really high tensile bolts are black in colour - but I assumed that this was something to do with the heat treatment.

Thats Zinz phosfate according to the links in this thread. And thats what we are going for.

We are hoping for 10 years life time without rust. the Zinc dicromate stuff has done 6-7 years now. Main problem is that the manufacturer has stopped their production and is now ordering it outside but with adding a "for the pain" fee so we now pay 285 Dollars for something we think we can get for perhaps 1/10 of that. its a big deal when the total demand is 2000ish bolts.

[Kelpiecross]

Thats Zinz phosfate according to the links in this thread. And thats what we are going for.

We are hoping for 10 years life time without rust. the Zinc dicromate stuff has done 6-7 years now. Main problem is that the manufacturer has stopped their production and is now ordering it outside but with adding a "for the pain" fee so we now pay 285 Dollars for something we think we can get for perhaps 1/10 of that. its a big deal when the total demand is 2000ish bolts.

My bolt supplier says the nice shiny bolts are just a neater form of zinc coating. They will sell their highest tensile bolts with this coating. Maybe you should just talk to various bolt makers.

[MatsNorway]

My bolt supplier says the nice shiny bolts are just a neater form of zinc coating. They will sell their highest tensile bolts with this coating. Maybe you should just talk to various bolt makers.

Been talking to our metallurgist who will look into it, and two plating companies. zinc cadmium is illegal. And im awaiting answer on the zinc phospate as the one i talked to was not convinced it was any better.

its about 1.2 dollar for zinc dichromate 6 worthy, 20my and with sealer on a M20 x 100 bolt

Dunno anything about the 6 worthy, the sealer i don`t know much about either but it was better with it.

Edited by MatsNorway, 09 January 2012 - 11:26.

[bigleagueslider]

MatsNorway,

The best type of corrosion protection for your bolts depends upon what type of environment they will be subjected to.

First of all, since you are coating screw threads, control of the coating thickness is very important. With plating on steel fasteners, the best choices are probably electroless nickel or IVD aluminum. Both are durable even in marine atmospheres, and the coating build-up can be precisely controlled.

http://www.pfonline....sion-protection

[Kelpiecross]

[quote name='MatsNorway' date='Jan 9 2012, 22:21' post='5473349']

http://429mustangcou...new_page_26.htm

[MatsNorway]

http://en.wikipedia....version_coating

Zinc phosfate is no go.

My plating man talked about

iso 2081 El-Zn+blue chromate

He believed it to be better than the yellow

iso 2081 El-Zn+yellow chromate

i have asked for the document divisjon to check them out, so i can possibly look at the specs.

[MatsNorway]

MatsNorway,
best choices are probably electroless nickel or IVD aluminum. Both are durable even in marine atmospheres.

http://www.pfonline....sion-protection

Is it expensive?

[bigleagueslider]

Is it expensive?

Cost is subjective. IVD is probably less costly than electroless nickel.

Conversion coatings (like phosphates) generally don't provide durable corrosion protection. They are mostly used as a surface prep for primer/paint.

slider

[MatsNorway]

Cost is subjective. IVD is probably less costly than electroless nickel.

And how does it compare to zinc dichromate? (yellow chromate)

[J. Edlund]

I don't know why, but ever since seeing the title of this threada phrase of 'vapor deposition' keeps appearing in my mind. Might have something to do with creating ceramic coatings on metallic parts used in engines... But then again, I'd hardly be surprised if I got something mixed up and was talking complete bollocks.

Chemical Vapor Deposition and Physical Vapor Deposition are used for the application of several hard, wear resistant coatings onto metals.

Because its supposed to give better protection thant Zinc Dichromate. It might not be much but if its a improvement it is good enough. I suggest you recommend a alternative. isnt it Zink phospathing on the 12.9 black unbrako bolts?. and they tend to last for some time.

the coating is for 43CrMo4 bolts and quenc? tempered C45 something steel.

The black coloured bolts use black oxide, which is a conversion of the surface into black iron oxide. Combined with oil it do offer some corrosion protection, but not much. Also popular on some hand tools and guns.

[MatsNorway]

I decided to buy the ISO 2081 standard that covers zinc coatings and so on.

The spec we will go for unless new info arrives: Fe/Zn25/ER(190)/8/D

25micron? 0,025mm thickness. zinc coating with hydrogen embrittelment relief threatment. 190 degrees for 8 hours. D means Dichromate. that yellow stuff. its ratet equal to the green stuff. Its all about the thickness..

hot galvanising makes the bolt bend up..

The bolt is currently under testing to try to find out about their heat threatment. And zinc layer measuring (hopefully) so that we can get pointers about life time expectancy.

We decided to do it properly as this is for brake calipers to trains. This is all about safety.


There is something called sealers but no standard on it yet just manufacturer claims. Have not bothered with it. Its just extra rust protection.

Edited by MatsNorway, 13 February 2012 - 07:07.

[MatsNorway]

Most of the bolts where quenc tempered to about... 600vickers?? only about 1mm deep.

How does one say that on the technical drawings? does anyone have a picture?

No one knows about the TQ+ T.

[REN_AF1]

Most of the bolts where quenc tempered to about... 600vickers?? only about 1mm deep.

How does one say that on the technical drawings? does anyone have a picture?

No one knows about the TQ+ T.

I might be a bit late on this thread, but have you considered:
http://www.dacromet.com/hcoat.htm

We have ALL our std. bolt supplied with this in an effort to phase out Crome 6, and have had no complaints.
I initially where concerned that the coating would flake/chip during use, but it is remarkable resilient to mechanical impact. In fact we have assembly lines using impact wrenched on some of our products, and even here I have never seen damage to the bolt surfaces.

According to our bolt supplier, the wind turbine industry is using Dacromet coating for their off shore applications too, so the corrosion class is definitely on par with what else is out there.

R

[MatsNorway]

"Salt Spray DACROMET®: 500 hrs minimum"

As a comparison the Zn25/D does 360hours in neutral salt spray test.

Impressive. How is it priced?

The bolts and everything with it is finished.

Edited by MatsNorway, 19 March 2012 - 15:01.

[REN_AF1]

"Salt Spray DACROMET®: 500 hrs minimum"

As a comparison the Zn25/D does 360hours in neutral salt spray test.

Impressive. How is it priced?

The bolts and everything with it is finished.

I believe we have our bolts specified to a 280h equivalent (were not really in a corrosive environments) but prices are on par with conventional yellow passivated items.

The real benefit is that it can be used on hardened items without the risk of hydrogen embrittlement.. (Yes I know I am a bad and ignorant person since I cant be bothered much about Crome 6 problems :-)

R

[MatsNorway]

The real benefit is that it can be used on hardened items without the risk of hydrogen embrittlement..

The zinc coating spesified does include a hydrogen embrittelment relief threatment. Is there no need for such threatment with the Dacromet?

[giffo]

Dichromate of Mag gearboxes

A question here I hope someone can give advice to.
FT200 gearbox, It has been stripped, casing was very black, now washed with kero and now it is only a faded black.

How or what is used normally to reblacken the surface to the original? (Boot polish maybe?)

Cheers in advance ot those who can help.

[MatsNorway]

Worth mentioning is that the bolts was ordered with dichromate (yellow stuff right)

But they are different to the old ones in the color. They are shiny white now. crome in the color. hmm.