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COATINGSPRO MARCH 2017 21 Please note that any U V light w ith a waveleng th under 400 nm is considered dangerous to your sk in, and cer tainly your eyesight. In my ex per ience, a light in the 360 nm range works ver y wel l on organic oi ls of just about any t y pe, inc lud ing body f luids. I do sug gest you never inspect your hotel room w ith the light; you may be tr y ing to f ind a new room. You w i l l want to wear yel low U V block- ing glasses whi le using this light. T he costs of these lights, w ith the advent of LED ( light- emitting d iode) versions, has come dow n — but it w i l l sti l l cost you at least $100. e ASTM F22 "Standard Test Method for Hydrophobic Surface Films by the Water-Break Test" — aka the water mist method — is great. However, always keep in mind that it only works when used on non-hydro- phobic surfaces, such as steel. If there is any coating on the surface, it would be hydrophobic, and the water will bead up — just as it does on oil. Galvanizing Systems Q: A galvanized firefighting pipe system is being installed. A n external coating of red color is required, but an internal coating is not required, since it is galvanized. A modification on the wear plate is done on site, whereby fillet welding is done. T his caused some discoloration on the internal portion of the pipe. A fter feathering on the internal portion where welding is done, DFT measure- ments were taken on the galvanized area of the pipe internal. T he reading of the zinc coating is 150 microns (5.9 mils). My question is this: Will the heat from the welding cause the zinc coating to melt and cause the adhesion bonding between the substrate and zinc to weaken? I ask this since the DFT of the zinc still exists. Does it need to be repaired? If so, would a modified epoxy coat over the affected area be enough? W hat would be the repair procedure? A: A s the weld zinc coat bur ns out, it w i l l require add itiona l zinc coating. You shou ld use a zinc-r ich epox y coat to reinforce the zinc layer. Ma ke sure the weld is unifor m and f ree of water-hold ing recessions. A good sur face preparation is the basic requirement for good ad hesion of the zinc-r ich epox y coat. CP Notes From the Blog Wr i te in Re ad e r In q u ir y #363