This week, the overall grades of four Chemicals stocks are lower, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Ferro Corp.’s (NYSE:FOE) rating falls this week to an F (“strong sell”), down from last week’s D (“sell”). Ferro Corporation sells, distributes, markets, and trades propane and other natural gas liquids. For a full analysis of FOE stock, visit Portfolio Grader.

Arabian American Development (NYSE:ARSD) is on the decline this week, earning a D (“sell”) after receiving a C (“hold”) last week. Arabian American Development owns and operates a petrochemical facility located in southeast Texas, which specializes in high purity petrochemical solvents and other solvent type manufacturing. The stock gets F’s in Earnings Momentum, Earnings Surprise, and Sales Growth. For more information, get Portfolio Grader’s complete analysis of ARSD stock.

Slipping from C to a D rating, Albemarle (NYSE:ALB) takes a hit this week. Albemarle develops, manufactures, and markets specialty chemicals for the polymer additives, catalysts, and fine chemicals markets. The stock also gets an F in Sales Growth. To get an in-depth look at ALB, get Portfolio Grader’s complete analysis of ALB stock.

This week, Koppers Holdings’ (NYSE:KOP) rating worsens to a D from the company’s C rating a week ago. Koppers Holdings manufactures carbon compounds and wood treatments. The stock also gets an F in Earnings Surprise. For a full analysis of KOP stock, visit Portfolio Grader.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.