Critical Coating Applications

Is there such a thing?

Too many people in this industry do not know the role of coatings and surface modifications and who think of coatings as paint only. Let me inform you that there are many critical coating systems which provide the key solution for mechanical equipment to work and interact in the first place.

Currently in API, coatings are being classified as a critical supply chain process. Whether they are part of a critical bolt application, molybdenum with a finish of 16 or better, surface blast after welding and machining with passivation, or splash environment wear protection against hydrogen stress cracking. All of these systems have been critical in allowing oil tools to work. In many cases oil tools are nothing more than designed metal structures , which use rubber to act as the joints and coatings the skin of the operation.

A critical part that is usually missing is the understanding of how the rubber and the coatings work alongside the metal oil tools. Rarely, do I find anyone in #purchasing, #procurement ,or #supplychain that understands the process controls surround coatings. Time, temperature, use of rare earth elements, experience of applicators, lift capabilities, insulated facilities, are just a few things that can stop production cold.

Questions we should ask in written engineering specifications:

1. Do you have any coatings that over lap one another? How do you test for them?
2. Do you have any coatings that require a finish less than 32?
3. Do you have a log of your zinc phosphate tank readings prior to application as part of your certification for cure along with part metal temperature?
4. Is a rub test performed on PTFE applications to insure cure was met? If so what solution was used for solvent base and for water base applications?
5. Is there an internal NCR report when it comes to plating? What are the procedures you have for stripping? How many times is a part allowed to be stripped, before it is classified non-reworkable?
6. What percentage of acid do you use in your stripping process? How long is the part subjected to cleaner, stripper, plating chemistry?
7. Are you utilizing hexavalent coatings still? What are you going to use instead?

There are many questions that need to be asked and signed off on, when a coating is classified a critical application. This is a discussion that needs to ask questions from both sides and a proper understanding of the process and materials needs to be addressed.

Problems from the Field

In the field issues that I have personally worked on where critical application that were ignored, (Meaning there was no written process to check for issues at time of failure) or done incorrectly with little knowledge of being able to check to see if process was done right (inspector did not know what to look for due to experience with application).

Even though the quality procedures were handled by a certified inspector, that inspector did not know the job in which the tool performed, nor the correct way to test whether the coating was done correctly. Results were critical, because the tools were in the field less than 6 months, due to excessive corrosion. In other cases the tool failed and was the major cause of hydraulic pressure loss, uncontrolled shutdown and loss of tool control. All of which put service works at risk in the field and caused considerable financial cost.

-Ian MacMoy API 20P Chair and Coating Specialist with Bricco Metal Finishing.