Transformer Painting in a Nutshell

This is a picture of a transformer that R&H painted in Minnesota. It has 3 large radiator banks, and is located at a wind energy farm in southern MN.

Large substation transformers are a major capital expense for transmission and distribution companies. It is commonplace for companies to plan on using them for decades, sometimes even longer. If customer demand requires replacing a transformer with a larger one, often times the small one will be sold on the secondary market, and installed by another utility. While the chassis and other key components of a transformer are built to last, the paint coatings may not be. Regularly scheduled maintenance is an important function in the transformer lifecycle, and that should include inspection of coatings and timely maintenance painting as required.

This is a picture of the top of a transformer. Most of the paint has worn off, and large patches of orange are starting to show through.

This transformer is overdue for painting. While the sides of the unit do not show much weathering, you can see the top is much worse. This is very common and has to do with the top typically getting the most sunlight, and also pools of rain water accelerating the wear. From this point on, surface preparation costs are going to skyrocket. There are already some areas progressing from “tight rust” to “loose rust”. This raises the bar significantly in terms of surface prep required.

For the most efficient use of your maintenance budget, I recommend getting a maintenance coat before your equipment is showing major signs of corrosion. We can go further in depth on this at a later date, but the basic reason is as follows. In any given painting project, roughly half the money spent is allocated towards surface prep, aka cleaning. Removing rust, grease, failed coatings, and any other surface contaminants is absolutely mandatory before any new paint can be applied. The worse shape your transformer is in, the more work is required to get it “paint ready.” While a little grease or a lot of grease maybe doesn’t drastically affect the contract cost, the level of corrosion usually does.


Ideally, you should schedule painting before corrosion has taken over, or as soon as you see the slightest orange shades starting to show in the existing paint film. That way surface prep can be kept to a minimum, and involves just “cleaning” similar to cleaning dirty dishes. Now on the other hand, if you try to stretch out the maintenance schedule, you’re not necessarily saving money. Every day/week/month/year that goes by, increases your costs of surface prep. Ferrous metal surface prep basically starts out at just washing and scrubbing, and progresses up (in terms of cost) ending with sand blasting. Staying closer to the “washing” end up the spectrum will ensure you’re getting the most for your maintenance dollar. Let it go too long, and create too much loose rust, and you can literally get to the point where you might as well scrap it and buy a new transformer. Chances are it’s leaking all over the place anyhow.


While painting a transformer is not extraordinarily difficult, there are several key items that must be accounted for. The first item being safety! There are inherent risks involved with substation work, and it’s crucial that they are mitigated as much as possible.  Working in and around high voltage equipment does not provide for much room to “learn as you go”. Make a wrong move and it’s over. Literally and figuratively!


Most of the risk can be eliminated by following proper shut down and grounding out procedures. This is typically performed by the owners trained electrical personnel. Then its up to the painting contractor to perform their job satisfactorily. Proper training and use of lanyards, harnesses, ladders, and more is an integral part of providing a quality product and making sure everyone goes home safely.


While painting the body of a transformer is fairly straightforward, the radiator banks are another story. There is really only one way to accomplish it, while in the field, and that is by flow coating. Flow coating will give you a finished product very similar to if you disassembled the radiators, and hauled them to a shop to have them dipped. It is the only way (so far) to make sure that every single nook and cranny in the radiator gets coated.


Doing a good job of it requires extreme care, and due diligence on the part of the contractor. If the coating was to get applied too heavily, it could have a noticeable effect on the radiators ability to cool off the oil. In that case, your looking at major downtime, and major expense! If it’s too thin, it won’t last as long as it should. There aren’t really any good tools for measuring mil thickness of the paint, when you can’t even fit your arm in between the fins. Achieving the proper thickness is based solely off experience, and knowing what to look for (how the paint behaves) throughout the process. So it’s a delicate balancing act that requires a lot of experience by the applicator. 

So while transformer painting definitely isn’t rocket science, you’ll want to make sure that your projects are being handled by someone with experience. As you know, an ounce of prevention is worth a pound of cure and, its hardly worth painting to begin with if you don’t have a solid plan of action, and full faith that your contractor can take care of your needs.


Thank You, Bryce Raisanen
Feel free to like, share, comment, ask questions!

I’ve shortened the video below, to show just the cleaning portion of a transformer job. Responsible management got the painting scheduled before it was in too rough of shape, and with four people (I think?) we were able to complete all of the surface prep in short order.

This is a picture of a transformer that R&H Painting painted near Minneapolis, MN.

This is a picture of a large substation transformer that R&H painted near Blaine, MN.



This is another picture of the transformer that R&H painted nearby Blaine, MN.


This is a picture of a new paint job we put on a transformer in MN. We used a high gloss industrial coating from Induron coatings.


This is a finished picture of a large transformer that R&H painted in the fall of 2015 in central MN, not far from Minneapolis.


  1. Larry Rebman says:

    He’s right – the integrity of the transformer tank and radiators is critical to keeping the insulating oil and core assembly free of contaminants, to maintaining the cooling and voltage ratings and protecting the environment from spills. Corrosion can be hard to repair, and these thing are heavy, very expensive to ship. Keeping the tank and radiators intact maintains proper oil level to preclude a possible cause of equipment failure, fire and power outages.

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