Thermal spray coatings have a limited life and the time between inspections is crucial in planning for the recoating of components before a failure occurs.
Set a Baseline Inspection Schedule
The initial inspection interval depends upon the operating conditions. For instance, in abrasive or corrosive applications or where operating temperatures exceed 500°C, it is recommended to inspect coatings every 3 to 6 months. In less severe operating conditions, coatings can be inspected every 12 months. It is recommended to use the coating manufacturer’s data as a guide for the initial inspections and then alter as necessary based on site experience.
Watch for These End-of-Life Signs
Signs of coating end of life include visible surface attack such as spalling, blistering and pitting. Porosity breakthrough where corrosion products are observed to be leaking through the coating to attack the substrate surface is also indicative of coating failure. Measuring coating thickness and recording loss on a consistent basis can also highlight coating wear. A general rule of thumb is to plan for a recoating life of 20-25% thickness wear.
Use Gauges to Track Wear Between Shutdowns For more on thermal sprays, take a look at www.poeton.co.uk/surface-treatments/thermal-metal-sprays.
Regularly measuring and recording the thickness of coatings using such gauges between shutdowns provides a consistent and accurate method of determining wear rates. Instead of allowing coatings to fail catastrophically between planned shutdowns, the resulting data can help predict and allow for the necessary maintenance to be carried out prior to the next shutdown. Thermal Sprays are worth getting right.
Decide Between Touch-In and Full Recoat
In all cases the decision to undertake a touch-in of the topcoat as opposed to a full recoat depends on the condition of the bond coat. If in doubt, carry out adhesion tests to confirm the integrity of the bond coat prior to any touch-in work. uk/surface-treatments/thermal-metal-sprays/).
Build a Site-Specific Interval Over Time
Record all findings, all thickness measurements and the date of any re-coating in simple logs. uk/){rel=”nofollow”} to form a recognised inspection regime after a couple of coating cycles. As the intervention data is gathered for each part, (not for the whole site) it can then be refined over time to form the optimal interval for that part in that environment.
A simple log of findings, readings and recoat dates from inspections of components in service, when done as part of a planned preventive maintenance inspection, forms the best tool to ensure that items that have been coated are kept in service for as long as possible before failure.
