PaintSquare.com
      | Connect Follow us on Twitter Like us on Facebook
About | Subscribe | Advertise
  

 

Download our free Wastewater Treatment Coating Systems eResource Book

Problem Solving Forum

| More

May 6 - May 12, 2013

How does the concave or convex curvature of a surface affect the dry film thickness reading?



More items for Quality Control


Selected Answers

From Tom Swan of M-TEST on June 21, 2013:
I am assuming the question refers to how the DFT readings are effected  when using a Magnetic DFT gauge. On a flat surface, the magnetic field is spherical and decreases by the cube of the distance from the surface being measured. Once the strength of the field is determined (reason for 2-point calibration), it is easy to calculate the DFT if you know the strength of the magnetic field at any given point. In theory, it will work for any DFT thickness, but in reality, it is determined by the size of the coil in the probe generating the field. That is why DFT probes get larger as the thickness they will measure gets greater. As far a curvature, picture a fixed- ize bubble on a flat surface, As you bend the surface away from the bubble (convex), the bubble begins to flatten out. Assuming the bubble was 3 mils tall when you started, as you begin to bend the surface, the top of the bubble gets closer to the surface decreasing the distance to 2 mils or 1 mil, even though the size of the bubble did not change. On a convex surface the magnetic field is bent towards the surface making the measured distance less than it actually is. On convex surfaces the field flattens. On a concave surface just reverse what I just said. The magnetic field bulges out. By doing a 2-point calibration, you let the meter know what the shape of the magnetic field is so it can judge the distance based on both the shape and the strength of the magnetic field. Since the magnetic field decreases at the cube of the distance to the surface, small differences in the magnetic field strength can magnify errors based on curvature. That being said, except with relatively small objects such as small piping, the errors are generally pretty small.

From Mark Puckett of Orfanos Contractors, Inc. on June 21, 2013:
You need to contact the gauge manufacturer of the specific instrument you are using with the details of what you actually measuring.It would depend on the type of gauge and probe utilized and the orientation of the gauge, among other factors, as well as the substrate and coating or lining being measured.

From Karen Fischer of Amstar of WNY on June 12, 2013:
I believe the question is asking how the curvature affects the READINGS taken of the ry film thickness, not how the curvature affects the paint. Seems to me that logically, it would depend on the degree of curvature and how "flat" the Type 2 Gage can rest on the surface. The ability of the probe region of the gage to "rock" on a convex surface or be held further away from the pinpoint on a concave surface is likely to affect the accuracy of a reading.

From Gerald Burbank of Burbank on June 10, 2013:
Depending on the curvature, convex surfaces can cause wet coatings to pull away from the peak of the curve. The steeper the angle, and the less viscous the coating, the greater the effect that surface tension will have (as with edges), by thinning the wet film at the peak. Conversely, fluids will tend to gather in the trough of a convex surface due to surface tension along the edges. As stated in Mr. Tibbetts' post, other factors come into play as well. I imagine that ambient conditions and gravity plays a role as well. Gravity would tend to offset some of the effects of surface tension on a convex curve where the peak is inverted. Estimating the degree to which wet coatings would tend to flow toward or away from the peaks and troughs of a curved surface would need to take into account all of these variables.

From Ken Tibbetts of K C Tibbetts Company on June 6, 2013:
It all depends on the method of coating application--dipping, hand, robot, electrodeposition, etc. Of course, there's substrate temperature, basic material from which the substrate is made, the coating itself, size of object, atmospheric conditions, and lots more. There is no one right or wrong answer to the question. Give me details and I'll give a specific answer,

Please sign in to submit your answer this question    

Tagged categories: Coating / Film thickness; Dry Film Thickness (DFT)


Current PSF Question | Submit a PSF Question | Full PSF Archive

KTA-Tator, Inc. - Corporate Office
KTA-Tator
Coatings Inspection

Any structure, any height, any place - A qualified coatings inspector is always available. Call 800-245-6379.


Fischer Technology Inc.
MP0R with rotating display screen

Automatic rotating display screen just like your smart phone. Click for Video
Call 800-243-8417


SSPC: The Society for Protective Coatings
http://www.sspc.org/

Join SSPC and Enhance
Your Career !


Elcometer, Inc.
Elcometer 266
DC Holiday Detector

Easily Finds Pinholes, Flaws & Thin Spots; Safer, More Reliable Testing; Voltage-Adjustable Keypad; Dual-Safety Switch On Handle.


WINOA Group
W Abrasives : Maintenance Pack

The blasting company able to reduce your maintenance costs up to 30% by fine-tuning consumption, and increasing productivity. Visit us during the GIFA (Hall15 - D14).


Advanced Recycling Systems
ADVANCED RECYCLING SYSTEMS (ARS)

Recycling Machines, Dust Collectors, Rapid Deployment units are time-tested and approved for the rugged industrial environment. Contact ARS today!
(330)536-8210


DeFelsko Corporation
PosiTector 200 for concrete

Rugged, simple and affordable coating thickness gage for concrete measures protective coatings including polyurea.


Commercial Sand Blasting & Painting Ltd.
Reliable Service & Superior Workmanship

We’re ready to meet any of your protective coating and lining needs. We can work on your site or in our facilities, with large shops (60,000 sq ft), 40 acres of yard space, and cranes and forklifts on site.


HoldTight Solutions Inc.
NO FLASH RUST -
NO CONTAMINANTS

Our HoldTight®102 salt remover & flash rust preventer prevents flash
rust by removing surface contaminants. It has no equal; only wannabees.
Contact us for your
nearest distributor.
(800) 319.8802 sales@holdtight.com


Blastox/The TDJ Group, Inc.
Blastox - One Step
Lead Abatement

Don't waste $$ on added labor steps with other methods. Don't mix, meter or apply at the job-site. Avoid strict hazardous waste rules.
Let your painters paint!

 
 
 
Technology Publishing

The Technology Publishing Network

The Journal of Protective Coatings & Linings (JPCL) PaintSquare
Durability + Design Paint BidTracker

 
EXPLORE:      JPCL   |   PaintSquare News   |   Interact   |   Buying Guides   |   Webinars   |   Resources   |   Classifieds
REGISTER AND SUBSCRIBE:      Free PaintSquare Registration   |   Subscribe to JPCL   |   Subscribe to PaintSquare News
MORE:      About PaintSquare.com   |   Privacy policy   |   Terms & conditions   |   Site Map   |   Search   |   Contact Us
 

© Copyright 2000-2015, Technology Publishing / PaintSquare, All rights reserved
2100 Wharton Street, Suite 310, Pittsburgh PA 15203-1951; Tel 1-412-431-8300; Fax 1-412-431-5428; E-mail webmaster@paintsquare.com