VISUAL KEYS For Successful Base Material Preparation Welcome to Visual Keys for Successful Base Material Preparation. The purpose of this presentation is to familiarize you with the visual keys that are associated with preparatory steps for commonly used base materials. After viewing this presentation you should be able to identify commonly used base materials by performing a test etch on a sample area of the surface to be plated. And you should have a good understanding of the visual keys associated with each step of the preparatory procedures for commonly used base materials. VISUAL KEYS For Successful Base Material Preparation Copyright © 2012 SIFCO Applied Surface Concepts

Base Material Identification Obtaining good adhesion of a SIFCO Process deposit begins with proper identification of the surface being plated on. Occasionally, the operator is misinformed as to the identity of the base material or is not informed or aware that a coating is present on the surface. This can lead to adhesion problems. An alert operator will frequently detect incorrect identifications or the presence of coatings by carefully watching the etching operation. Each base material requires a specific preparatory process to ensure that the plated deposit has good adhesion. One of the most important steps needed to ensure good adhesion of a brush plated deposit is to make sure that you have correctly identified the base material you’ll be plating on.

Base Material Identification

Preparation A SIFCO Process preparatory cycle consists of a number of operations, each one performing a specific function. The number and types of operations, and the solutions used, depend on the base material and not the plating solution to be used later. Each operation should be carried out properly to ensure obtaining maximum adhesion. The operations are properly carried out when: The proper solutions are used in the proper sequence. The solutions are used in the proper direction of current flow, i.e. forward current or reverse current. The operations follow each other as rapidly as possible and with the surface not being allowed to dry between operations. The desired results are obtained in each operation. Visual tests are important and the operator should pay particular attention to them. Preparing a correctly identified base material involves a series of operations or steps. Each step performs a different function. Please note that it is the base material that determines the preparatory steps to be used.

Electrocleaning Etching Usually performed first Removes the last traces of dirt, oil, and grease Removes the light oxide films on some metals such as copper. Usually done in forward polarity Etching Performed in reverse polarity Removes oxides, corrosion products and smeared and contaminated surface material Ok, let’s start with a brief description of each of the different types of operations. An electrocleaning or cleaning and deoxidizing operation is usually performed first on most base materials to remove the last traces of dirt, oil, and grease. It also removes the light oxide films on some metals, such as copper. In most cases this step is done in forward polarity. The visual key for a successful electrocleaning operation is in the following rinse. If a part is sufficiently electrocleaned, there will be no waterbreaks on the surface of the rinsed part.

Desmutting Activating Follows the etch on some base materials Removes loose layer of insoluble material on the surface. Done in reverse polarity Activating Removes passive oxide film No visual key (except for chrome) Done in forward polarity Temporary state Some materials when etched will result in the formation of a loose insoluble material on the surface. The desmutting operation, done in reverse current, removes that film. The resulting surface should be uniformly lighter in color.

The Rinse In most cases, a thorough water rinse should follow each preparatory step. One of the most critical is the rinse after the electrocleaning operation. If water “breaks” on the surface, either the electrocleaning time was too short or the voltage was too low, and the operation should be repeated. Finally, let’s discuss the rinse. With the exception of the activation step, a rinse will follow each preparatory operation. A good rinse will use enough water to completely displace the solution from the previous operation. And always, always, always, Look for water breaks!

Water Break A “water break” is when a water film breaks into beads such as on a waxed car. If this occurs, the surface is not clean! Water Break Clean Surface Look carefully for water breaks. If you’re rotating a part, you may want to briefly stop the rotation and observe. If the water does not sheet off the part, you’ll need to repeat the operation and perhaps use a higher voltage or a longer duration or a combination of the two.

Visual Keys The following series of slides shows what the operator should look for in each of the preparatory operations. Consider: Appearance of the base material before and after the operation Appearance of the cover and the solution in the cover after the operation. Now that we’ve touched on the fundamentals of base material identification and the various preparatory operations, it’s time to take a detailed look at the visual keys for each of the preparatory steps used on the most common base materials you’re likely to run into. In general, before you start a preparatory operation, take a few minutes to review the visual keys for that base material. If you know what to look for, and you take the time to look, and you proceed from one step to the next only if you see what you are expecting, then you should have a successful outcome with your preparatory operation.

Carbon Steel This is carbon steel before being etched. This particular sample has a uniformly light and grainy appearance that is a result of the processing operation to produce the panel.

Carbon Steel Before After This is carbon steel after being etched. Note that the surface is uniformly grey and dull in appearance. The lack of a dark smut on the surface indicates that it is a low carbon steel. Note that the cover material is clean and only very slightly colored by the residual solution.

Carbon Steel Before After This slide shows the carbon steel after being desmutted. The surface appearance lightened and the color of the cover material has darkened only slightly.

300 Stainless This slide shows a 300 series stainless steel after electrocleaning and before being etched. It has a satiny to semi shiny appearance.

300 Stainless Before After Note the uniformly dull appearance of the etched surface of the 300 series stainless, and the light green color in the cover material.

400 Stainless This slide shows a 400 series stainless steel after electrcleaning and before etching. There are a few scratches present in the satiny to semi shiny surface.

400 Stainless Before After This particular alloy did not produce a very dark blue-green coloration in the cover, indicating a low carbon content. Note the uniformly etched surface that is more dull in appearance than before etching.

400 Stainless Before After Desmutting this panel did not significantly lighten the surface appearance, but there is some indication of a light smut in the cover.

Monel This slide shows a monel panel after electrocleaning and before etching.

Monel Note the uniform light gray surface of the panel and the smut that has developed in the cover.

Monel After desmutting the surface again appears clean.

Copper This slide shows copper before and after electrocleaning

Copper Note the uniformly clean etched appearance of the panel and the blueish color of the solution in the cover.

Chrome This is a very shiny chrome deposit before electrocleaning

Chrome After the etch the surface remains shiny. The color of the solution in the cover is bright yellow.

Chrome This slide shows how the activation step, when properly carried out darkens the surface of the chrome.

Summary Successful adhesion hinges on correctly identifying the base material and performing the correct preparatory operations for that material in the right sequence and ensuring that the visual keys are observed for each step. In summary, successful adhesion hinges on correctly identifying the base material and performing the correct preparatory operations for that material in the right sequence and ensuring that the visual keys are observed for each step.