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aluminium motorcycle wheels - pc'ing cause failure?

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  • aluminium motorcycle wheels - pc'ing cause failure?

    Has anyone heard of any stories where powder coating aluminium motorcycle wheels effected the strength.... and caused failure?

  • #2
    Re: aluminium motorcycle wheels - pc'ing cause failure?

    I have never heard of a specific case where that has happened, but it could. It depends on the alloy and method of manufacture. 6160-T6 has a tendency to become structuraly unsound when it's heated to 400f for extended periods of time. Vacume castings and extrusions in most cases will not be an issue. Basically if someone comes to you with a stock wheel from HD or where ever you should be ok. If someone comes to you with a one off CNC cut "billet" wheel you should ask some questions before you heat it up. The most important thing to ask is: What is the alloy? If you can't find that out you should probably not heat it up too much. If you do it anyway you need to ask: How's my liability insurance? There are more powder manufacturers making low cure powders now, so that may be an option for some of the more exotic alloys. I would turn down a job before I took a risk on an unknown alloy. I went and purchased a metalurgists hand book that gives specs on hundreds of alloys including max temp. It was VERY expensive but has come in handy a few times.


    • #3
      Re: aluminium motorcycle wheels - pc'ing cause failure?

      if that was the case i put well over 300 rides in harms way... there is not enought effect on the metal to matter the bearings need to be remove or they will be harmed .. but other than that the 300 + set's of wheels i did are racking up miles ... Don't worry about it


      A red flag has been raised here. Please refer to my posting further down
      Last edited by mcaswell; 09-23-2005, 11:26 AM.


      • #4
        Re: aluminium motorcycle wheels - pc'ing cause failure?

        Does anyone know where I can find out at what temperature heat-treatable alloys begin to undergo a change in their structure? I'm concerned not only about strength but also intergrannular corrosion forming later on (from the slow cooling).
        Steve Dold


        • #5
          Re: aluminium motorcycle wheels - pc'ing cause failure?

          ASM International is the world's largest association of materials engineers and scientists. We are dedicated to informing, educating, and connecting the materials community to solve problems and stimulate innovation around the world.

          How's the fishing been sdold?


          • #6
            Re: aluminium motorcycle wheels - pc'ing cause failure?

            Attn Customsound

            Just before you posted this, another guy was saying that there is scientific evidence to show that some aluminum alloys will fatigue and cause failure when exposed to excessive heat. After you posted this, another guy asked for more information on the subject.

            I've been in business selling coatings and resins and repair materials for 30 years, and I've learnt not to recommend any product which may be used in a life threatening situation without scientific evidence that it will perform. All the tech depts of the numerous companies I worked for would squash any such idea immediately. That is why we have standards on all sorts of products.

            I doubt you are an expert in this field, and the fact that you have had no problems doesn't mean that it won't happen. I hope you have good liability insurance, although somehow I doubt it.

            All I want you to do is moderate the forum, not trailblaze ideas that aren't proven, and hold potential danger. Our terms and conditions absolve us of anything you say, but it could still cause a problem if a hungry lawyer got hold of it. But worse, you and I, would be completely guilt ridden if we discovered that someone died as a result of your most unscientific assumption that just because YOU had painted 300 wheels with no problems to date, it was ok. Maybe testing will show that the wheel will fail in 2 or 3 years?

            A customer raised a red flag here, we cannot afford to glibly shrug off the problem.

            If someone comes back with specific evidence saying that alumiunum type X is ok to 450 f, then we know what to tell our customers. Whatever the outcome, we need to know the truth. Until then, I hold the red flag high!

            Now, if you don't like that, its too bad. I'll be sorry to see you go. I was hoping that you would take some direction and realise that we are trying to protect our, and your, interests. Maybe you'd like to rethink this, but I'll tell you now, our position on these things will not change.

            Mike Caswell

            Customsounds says:

            You know what .. I am done here. there is no problem in the post .. it is the truth .. remove me and i will be gone .. I had it[/QUOTE]
            Mike Caswell
            Caswell Inc
            Need Support? Visit our online support section at


            • #7
              Re: aluminium motorcycle wheels - pc'ing cause failure?

     check this link for the effects of heating aluminum.
              Mike Caswell
              Caswell Inc
              Need Support? Visit our online support section at


              • #8
                Re: aluminium motorcycle wheels - pc'ing cause failure?

                Thanks for the link.

                I have to agree with Caswell, better to err on the side of caution and find the correct information from someone who knows rather than find out the hard way. Granted many aluminum alloys you will get away with heating with no ill effects, but there are the exceptions, and without knowing what you're dealing with, you're taking someone's life in your hands and could be ruining any future life you may have. Just something to think about....



                • #9
                  Re: aluminium motorcycle wheels - pc'ing cause failure?

                  Just an idea for some. I've worked machine shop for years and dealt with aviation parts some of which were heat treated. If a heat treatment business can be found local give them a ring and check with them on the effects on aluminum. SS


                  • #10
                    Re: aluminium motorcycle wheels - pc'ing cause failure?

                    If you would like I can try to find the pdf format of the metalurgists reference that I bought and you can make it available as a download. It is definately public information and I believe it is used by the military to create their milspec standards(at least that's the claim in the book). If I can find it I will submit the link for anyone who wants to take the time to read it. I must warn you that it's very boring but the charts are easy to understand. However it is incumbent on the coater to coax the info out of the customer or manufacturer before applying any knowledge gained. I recently emailed a manufacturer asking for information on materials used in their product. It took a few days but I got a call from an engineer who gave me the info I needed. Better safe than caught in a law suit or reading about your mistake in the obituaries. With alloys getting more exotic everyday I like to be sure before I cure. Corny but a good policy I think.


                    • #11
                      Re: aluminium motorcycle wheels - pc'ing cause failure?

                      Although I have never heard of or read about it happening I supose it could happen. I'm with you guys on getting all the information available. At the very least it would be a good idea to make that information available to your customers and have some sort of waiver if they still want them powdered.
                      Lee Parsons
                      Rowlett, TX (East Dallas)


                      • #12
                        Re: aluminium motorcycle wheels - pc'ing cause failure?

                        I've read about it happening but can't find info on the temps at which it occurs. Thanks for the links, I'll take a look tomorrow night, I'm too tired from driving right now.

                        I spent a couple of summers ago experimenting with heat treating 2xxx alloy rivets, and testing them after various quenchings, non-quenchings, etc. It was interesting. The critical temp to get them to do what I wanted was 930 degrees, but I suppose something could happen at a lower temp. I just don't know. After treating they needed to be quenched and put in a freezer to hold the treated state. After taking them out and driving them, they were suddenly way harder, it was extremely cool to see it happen. If they were allowed to cool slowly in stead of quenching, they would harden and come up to strength (but be very hard to drive), but I've read that weird things happen that would cause intergrannular corrosion later on from the big grains that form during slow cooling. It's apparently not something that would show up right away or always be seen in a strength test. That's what I read anyway. But none of my books discuss other than the optimum treating temps.

                        I don't pretend to know much about this, so I thought I'd ask if anyone knew of a source of info. I don't plan to PC any critical structural parts but it would be nice to know anyway, just for the sake of knowledge. I don't THINK the PC temps are a problem, but I don't know why I think that. Thanks for the links and info, I'll be doing a lot of reading soon

                        Last edited by sdold; 09-24-2005, 01:12 AM.
                        Steve Dold


                        • #13
                          Re: aluminium motorcycle wheels - pc'ing cause failure?

                          From this link supplied by Caswell:


                          As I understand, of the three grades tested, 2014, 6061-T6, and 7075-T6, there should be no problems in curing PC on Al at elevated temps of 300 to 400 degrees. The decrease in tensil and yeild strength was substantial after 100 to 200 hrs but they said the results were cumilative over time. So unless a person was to coat a piece many times, the degradation of strength should not be a concern.

                          Is this the way you all understand it? Or am I missing something? I'm old enough to know interpretation is different to each person and would like to know if someone has a different interpretation than I?


                          • #14
                            Re: aluminium motorcycle wheels - pc'ing cause failure?

                            I posted the following a while back.... and it seems fitting to post again.
                            __________________________________________________ ______________

                            I though I?d pass along some information we acquired? We do a fair amount of aviation related items. For fear of dorking something up I got a hold of a metallurgist to see what we could and could not work with.
                            I believe the 6061 T6 is similar to the 7075 T6, I sent him an email today and asked about that specifically. The response will be posted.

                            His earlier information
                            Sorry to ask so many questions but the aluminum alloys come in a lot of flavors and their response to heat treatment is very varied. In general, 400F for 20 minutes would give you some small changes in mechanical properties. For many of the aluminum alloys the changes should be barely noticeable. A couple of alloys, however, could be a problem.

                            If you want to get a general text for your own reference there are a few from the American Society for Materials The "ASM Metals Reverence Book" covers just about any alloy, aluminum, steel, copper that you'd ever run across. The ASM "Aluminum: Properties and Physical Metallurgy" goes into more depth (could be overkill) and has a lot of heat treatment curves. The ASM also has a several volume set called the "Metals Handbook". The volume for general properties of aluminum would be ?Volume 2, Properties and Selection: Nonferrous Alloys and Special-Purpose Materials.?

                            First, regarding the Alloy 3003-T3. I can?t find a reference to this alloy in the T-3 condition. There are plenty of references to 3003 in the O condition (full anneal or real soft) and also in the H12, H14, H16 and H18. The H conditions refer to stain hardening?basically cold working. H12 is 1/4 hard and H18 is full hard. H18 is the equivalent of reduction by rolling mill to 75% of the original thickness. I?m not sure it is available in the T-3 condition.

                            If the alloy is strain hardened it can be annealed by heat-treating. Ignoring all the painful details that means the yield and ultimate strengths will drop while the ductility will go up. Typically 3003 is annealed by going to 775F with no hold time. Get to that temperature and the job is done. Obviously at lower temps you need to hold for a bit. Your 400F heat treatments are a long way from 775, so I?m confident that your 10-minute heat treatment doesn?t have much effect. Of course, if you furnace cools so slowly that the time at temperature is effectively very, very long, then you can get some annealing. If you heat-treat and cool reasonably fast you?re okay. If in doubt, heat-treat open the furnace door or pull the part out and put in on the shelf to cool.

                            As for the 2024 T-6, that alloy is a heat treatable alloy. Heat it up and hold for a while and the yield and ultimate strengths should go up. Conversely ductility drops. The T-6 heat treatment is usually at 365-385F for 11-13 hours. Your 400F processing is above the high end, but what the heck?you do it for 10 minutes as compared to 10 or more hours to get peak aging. I think you have almost no effect on the properties. The heat treating curves are not straight lines and are exponential, but your times are so short and the temps so close to actual heat treating conditions that you don?t make a dent in the properties.

                            As for 7075 T6, this is a bit tricky. Nominally the heat treatment is 245-255F for 24-28 hours. 400F for powder coating is a big overshoot and you could substantially change the properties in a few minutes. In the T-6 the yield strength is on the order of 75-80 ksi (ksi = thousands of pounds per square inch). From the limited data in my handbooks I don?t see any way this can be achieved at 400F. The alloy that starts in the T-6 almost immediately overages and softens. In fact, if you start with a 7075 part that is fully annealed (O-temper) it will harden to 75 ksi when heat-treated at 325F for only 1 hour. Past 1 hour it starts to soften to values below that of the T-6 condition.

                            Bottom line ? 3003 and 2024 alloy?you?re okay at 400F, the kinetics of aging are very forgiving at those temps. What you?re doing now couldn?t hurt these alloys. 7075, especially for something stressed and subject to fatigue, like a spinner?I wouldn?t do any heat-treating. Even if you start with a spinner in the O temper (if you could get it) it might warp when heat-treated at 325F and be out of round (just a worry, maybe not true). Not a big problem for an instrument panel, but an out of round spinner would be exciting.

                            As for the Mg alloys: Can you tell me which alloy the yokes are made from? Mg is out of my normal realm of knowledge and I need to do a bit of reading and literature searching before I can even render a sensible opinion.
                            Short story...10 minutes or so at 400F will not affect Alloy 40E.

                            Longer story...alloy 40E is now known as aluminum alloy 712. 40E is
                            the old and probably a trade name (712 is also known as SAE 310).
                            The unified numbering system came into being a number of years back
                            and replaced the trade and SAE numbers. Metallurgy is a confusing
                            mess of trade names, SAE, government specs and the like, many of
                            which are still around. The unified numbering system covers all the
                            aluminum alloys, but most (old) people still refer to the old trade

                            712 is used for sand casting and is usually used in the as cast
                            condition with no heat treatment. It has a higher melting point
                            than most of the other casting alloys, so it is useful in
                            applications where some sort of brazing assembly is required. It is
                            also more easily machined than some of the other casting alloys.
                            Downside is that it can be difficult to cast and care must be taken
                            to avoid cracking or defects during solidification.

                            712 is a natural aging alloy. The properties change during the first
                            few days after casting and generally stabilize after 21 days at room
                            temperature. Typical yield strengths are about 25000 psi. The alloy
                            can be furnace aged at 315F for 6-8 hours to achieve the needed
                            properties more quickly. 400F for 10 minutes won't do anything
                            significant. Maybe a slight overaging occurs, but the small reduction
                            in yield strength would not be detectable unless you did some sort of
                            sophisticated analysis...even then you might not detect any changes.

                            "Hi Larry,

                            I'm a little concerned about heat treating
                            6061-T6 at 400?F. I'm trying to find more data,
                            but what little I have suggests that the alloy
                            might overage quickly. The result would be a
                            drop in ductility and some drop in strength. Let
                            me do some more digging and I'll get back to you.

                            Hi Larry,

                            Wanted to get back to you about the 6061-T6. I
                            looked at some of the heat treating curves for
                            this alloy. At 400?F the reaction rates are
                            pretty quick. Starting with the T-4 condition
                            full hardness (T-6) can be reached in less than
                            an hour. If you're already in the T-6 condition
                            the alloy would overage quickly and you could see
                            a measurable change in mechanical properties.
                            The big effect would be a loss of ductility.

                            Things are much better at 340-350?F. If you can
                            process the coatings at those temperatures the
                            alloy would tolerate close to an hour. For
                            example if you start in the T-4 condition a
                            vendor would normally heat treat for 6-10 hours
                            at 350?F to get it in the T-6. Sticking another
                            40 minutes or so onto the time at temperature for
                            your powder coating wouldn't result in much of a

                            As for doing the frame of a helicopter...I
                            wouldn't sign off on the drawings for that one
                            regardless of the heat treatment temperature.
                            Complicated stresses, need to accept an
                            accidental overload, etc. Too much liability on
                            that job. I would suggest epoxy painting and
                            leaving the metallurgy alone.



                            • #15
                              Re: aluminium motorcycle wheels - pc'ing cause failure?

                              A good source for material properties.

                              Material property database with data sheets of thermoplastic and thermoset polymers such as nylon, polycarbonate, polyethylene; metal alloys, aluminum, steel, titanium, nickel, cobalt, and zinc alloys; ceramics, lubricants. Free search tools include mechanical property searches. Comparison and exports to Finite Element Analysis FEA software SolidWorks, ANSYS, ALGOR, and more.