Masking Issues

Chromic acid anodization (CAA) is the one of the oldest and most widely used processes in the aerospace and metal finishing industries. Type I Chromic Acid Anodizing is an electrochemical process that creates a thin aluminum oxide film by rapidly controlling the oxidation of an aluminum surface. The resulting aluminum oxide film is electrically non-conductive. CAA produces a thinner film than Type II and Type III Anodizing (hard coat) and produces enhanced drawing and forming characteristics and is often is used for flight-critical aluminum components that are subjected to high stresses.

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Masking caps and plugs need to fit properly in order to work as anticipated. Part III dives into what happens if those aren't quite right.

A new vehicle cab rolls down an e-coat line with 65 threaded holes which needed to be masked. A call is placed by a purchasing agent to a supplier that sells masking plugs. The size of the holes is relayed to the supplier who sends a variety of masking solutions for the holes in each part. Sounds simple right?

Not so fast… CFS was invited to evaluate why the current supplier’s plugs had failed - causing extensive tapping of all threaded holes after being coated. We quickly determined that the masking did not fit properly. Some were too small, others too big. The original supplier did not...

In Part I we discussed how masking can fail as the part surpasses it's life cycle. In Part II we will discuss what happens when the mask is not the correct one for the process being used. 

Often when our team members are on-site with large customers, we are presented with opportunities in new departments or on different production lines. We hear “it’s what we had on hand and it worked…kinda”. Sometimes having masking experts take a look can be a game changer.

For a recent customer, we saw a very cumbersome, mechanical masking solution being utilized. It required a bit of finessing to insert, the use of an impact wrench to apply and a tremendous amount of torque for it to expand and fill the void. Unfortunately, this pr...

A Guide to the Cost of Failed Masking in Finishing Processes

A rack of discards sits in the middle of the room. Shelves of streaked parts, awaiting their disposal. “What happened”, we ask? “Oh, the plugs must have leaked as they were coated”, was the reply. We discuss whether rework is an option, but in the end, it is cheaper to just scrap them rather than strip and start over. “That is why we called you”, they sighed.

Masking can fail for several reasons:

1. The mask is not correct for the process being used
2. The mask is not sized properly
3. The mask has reached its end of life

For this article we will focus on the third mode of fai...