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Cylinder coatings

Discussion in 'Mechanic and Repair' started by zmelli, Oct 13, 2012.

  1. zmelli

    zmelli LawnSite Member
    Messages: 57

    It there a difference between chrome-impregnated and chrome-lined cylinders?
  2. zmelli

    zmelli LawnSite Member
    Messages: 57

    Google search found this "TRhe heart of any chainsaw engine is the cylinder. Some have chrome plated cylinders...and sooner or later the chrome starts to peel off..kaput !

    Some have chrome impregnated cylinders, where pressure drives some chrome into the pores of the aluminum....somewhat better.

    The best saws have a thin cast iron liner for cylinders...they are more expensive to produce, but make a much longer lasting engine..

    Just my two pennies.... ""
  3. zmelli

    zmelli LawnSite Member
    Messages: 57

    Husqvarna 326LS has "Hard chromium plated cylinder bore provides increased durability and extended product life
  4. kawakx125

    kawakx125 LawnSite Bronze Member
    Messages: 1,130

    i've never heard of chrome flaking off of a cylinder that is properly lubricated...they use chrome or cast iron liners for the hardness. cast iron obviously weighs a little more. properly taken care of you're fine with either, husqvarna makes good stuff
  5. zmelli

    zmelli LawnSite Member
    Messages: 57

  6. zmelli

    zmelli LawnSite Member
    Messages: 57

    Chrome Plating
    Moving a notch up the cylinder rework food chain is chrome plating. Here, the worn barrel is ground oversize, and then a layer of chrome is deposited via electroplating to bring the cylinder back to new dimensions. (A good chrome plating job is about .015" thick. A bargain basement one might be a lot thinner.)
    Standard pistons can then be used, but chrome cylinders require special cast iron rings (instead of the chrome-plated rings used with steel cylinders). An often-overlooked disadvantage of chrome cylinders is that the relatively soft cast iron rings wear out faster than ordinary chrome rings do.

    Chrome is a very hard and durable wear surface—even more so than nitrided steel—and has the additional advantage of being almost immune from corrosion. However, a smooth shiny chrome surface is not oil-wettable, so something must be done to the chrome to allow an oil film to adhere to it.

    The traditional solution to this dilemma, used successfully for decades, is channel chrome. In this process, when chrome has been electroplated to the desired thickness, the current flow in the plating tank is reversed for a short (and critical) period of time. This results in a chrome surface that isn't smooth but has numerous microscopic fissures (called channels) that provide a "foothold" for oil to adhere.

    There are a couple of problems with channel chrome. The channelling process is apparently more black art than precise science, and it's difficult for even the best plating firms (such as ECI in San Antonio) to get consistent results. If the channels are too shallow, the cylinder won't make TBO. If they are too deep, oil consumption will be high. Even the very best channel chrome cylinders tend to burn a lot more oil than steel.

    Lots of folks love chrome. They believe that its durability and corrosion resistance are worth the tradeoff in oil consumption. Chrome is a particularly good choice for operators with extreme vulnerability to corrosion, such as salt water floatplanes and highly seasonal operations.
  7. kawakx125

    kawakx125 LawnSite Bronze Member
    Messages: 1,130

    you seem to know all about it already why ask the question?
  8. BigFish

    BigFish LawnSite Platinum Member
    Messages: 4,158

    Sounds more like a bunch of quotes from Googled sources , rather than actual knowledge!!
  9. zmelli

    zmelli LawnSite Member
    Messages: 57

    Yep, That is how I learn
  10. joe billy

    joe billy LawnSite Member
    Messages: 35

    What can you tell me about the plating that. Kohler uses in some of their 25 hp engines ?
    I've seen the plating come loose in chunks , as if it were scratched by a bear. The most common problem I've seen is pinholes in the plating. I believe the plating is only .010 thick ? What causes these problems ?

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