Frequently Asked Questions
Substrates are normally prepared by grit blasting prior to coating, but in some cases delamination may occur. There are a number of things that can be done to try and eliminate the issue. Trial and error is the fastest policy in this case, but you must check your surface preparation first.
Check:
- That your substrate preparation is adequate and the blast media and blast parameters are appropriate for your coating type and thermal spray process. If you do not degrease and grit blast your substrate immediately before spraying to a near white metal or white metal finish then this is the most likely cause of delamination. Your spraying parameters. If you are too close to/far from, the substrate you may be causing the problem. Likewise if you are using equipment that has not been calibrated for a long time.
- Try and work to standards as these will help you with best practice and quality
Try some of the following:
- Changing the grit type and/or the grit blast size. This will help provide an anchor for the coating. This becomes critical as the hardness of the substrate increases. The grit type and size is also dependent on spraying process and consumable selection.
- Try to put the coating down in layers that are not too thick (check what is recommended with the supplier of both the equipment and consumables)
- Look at the substrate and check its temperature. Significant oxidation of the substrate should not occur because of spraying. Cooling may be required.
- Try preheating the substrate prior to spraying e.g. with a few passes of a spray gun.
- If all has failed, try a bond coat. Your equipment or consumable supplier should be able to recommend a suitable bond coat. For example good bond coat materials include nickel chrome and tungsten carbide coating materials.
Further information on surface preparation prior to application of thermal spray coatings can be found here:
See further information about Materials & Corrosion Management or please contact us.